| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 636.1 | Payload Summary for 06/18/90 | 4347::GRIFFIN | Dave Griffin | Wed Jun 20 1990 19:45 | 35 |
| Payload Status Report
Kennedy Space Center
Monday, June 18, 1990
George H. Diller
407/867-2468
FTS 823-2468
GAMMA RAY OBSERVATORY
On Friday, June 15, there was a pressurization test of the
orbit attitude thrusters (OAT). They were pressurized with
gaseous nitrogen to 10% above flight level.
Today there is a partial loading of hydrazine attitude
control propellant to wet seals in a pair of thrusters which will
allow these seals to seat. This could reduce or eliminate a
small amount of leakage in one of the thrusters which was
detected in early testing. Twenty pounds of fuel, or about 2 1/2
gallons, will be loaded aboard. Tomorrow the system will be
repressurized to begin three days of leak checks.
In other work, mechanical preparations were begun for an
upcoming functional test scheduled for next week. Also, thermal
blanket closeouts have started on a limited portion of the
spacecraft.
From: [email protected] (Peter E. Yee)
Newsgroups: sci.space
Date: 19 Jun 90 18:23:26 GMT
Organization: NASA Ames Research Center, Moffett Field, CA
|
| 636.2 | Payload Summary for 09/26/90 | 4347::GRIFFIN | Dave Griffin | Thu Sep 27 1990 18:43 | 23 |
| From: [email protected] (Peter E. Yee)
Organization: NASA Ames Research Center, Moffett Field, CA
Payload Status Report
Kennedy Space Center
Wednesday, September 26, 1990
George H. Diller
407/867-2468
FTS 823-2468
GAMMA RAY OBSERVATORY
This week, testing of GRO is underway using the Goddard
Space Flight Center's remote Compatability Test Van. Tests
include radio frequency system checks of the spacecraft's command
and data handling module and its associated communications links.
Testing of this subsystem characterizes its performance and
establishes any trends in the performance of the module since it
was last exercised at TRW's Space Park facility in California.
|
| 636.3 | NASA's "quick peek" at GRO (launch date is wrong) | 4347::GRIFFIN | Dave Griffin | Wed Nov 28 1990 00:03 | 29 |
| GAMMA RAY OBSERVATORY
GRO, the gamma ray element of the Great Observatories
program, will be a free-flying observatory with an
operational lifetime of four years. This lifetime can be
extended to eight years through reboost of the spacecraft
and refueling of its Multimission Modular Spacecraft
modules. The Gamma Ray Observatory will cover a wavelength
range of 0.05 to 30,000 Mev, and its 15,790-kg mass will
orbit at an altitude of 350-450 km and an inclination of
28.5 degrees. Its complement of science instruments,
developed by Principal Investigators, includes an oriented
scintillation spectrometer experiment, a Compton telescope,
an energetic gamma ray experiment, and a burst and transient
source experiment. The Compton telescope has been developed
in the Federal Republic of Germany.
Scheduled to be launched by the space shuttle in 1990,
the Gamma Ray Observatory will:
(1) study gamma ray emitting objects originating in our
galaxy and beyond;
(2) investigate evolutionary forces in neutron stars and
black holes;
(3) search for evidence of nucleosynthesis; and
(4) search for primordial black hole emissions.
|
| 636.4 | GRO payload status report - 01/17/91 | PRAGMA::GRIFFIN | Dave Griffin | Mon Jan 21 1991 10:52 | 44 |
| From: [email protected] (Peter E. Yee)
Date: 18 Jan 91 18:45:33 GMT
Organization: NASA Ames Research Center, Moffett Field, CA
Payload Status Report
Kennedy Space Center
Thursday, January 17, 1990
George Diller
407/867-2468
FTS 823-2468
GAMMA RAY OBSERVATORY (GRO) STS-37/Atlantis
Yesterday the alignment of the spacecraft's two sun sensors
was accomplished.
Fueling of GRO for its on-orbit activity was completed late
last last week as scheduled. A total of 4200 pounds of
monomethyl hydrazine was loaded aboard (three to four times more
fuel than is required by most spacecraft). This large quantity
of fuel will permit extended mission operations.
On Monday and Tuesday, work was performed to remove the
spacecraft's test batteries and then reinstall the six nickel
cadmium flight batteries which are housed in two modular power
supply units (MPS). The MPS units were installed on the
spacecraft yesterday and then the batteries were charged. Today
the spacecraft is being powered up.
The Instrument Switching Unit (ISU) which was removed on
December 23, shipped to TRW, repaired and then retested, was
reinstalled on the spacecraft yesterday. Integration and system
tests are scheduled to start Friday. The ISU contains circuitry
which controls electrical signals to various equipment throughout
the Observatory.
GRO is scheduled to be moved from its current location at
the Payload Hazardous Servicing Facility (PHSF) to the Vertical
Processing Facility (VPF) on Feb. 6 where final tests will be
performed and work will be done to prepare it for integration
with the Space Shuttle Atlantis.
|
| 636.5 | Gamma Ray Telescope set for launch | PRAGMA::GRIFFIN | Dave Griffin | Thu Jan 31 1991 19:23 | 84 |
| From: [email protected] (WILLIAM HARWOOD, UPI Science Writer)
Date: 31 Jan 91 16:29:03 GMT
UPI SCIENCE
CAPE CANAVERAL, Fla. (UPI) -- NASA's Gamma Ray Observatory has been
thoroughly tested to ensure it has no hidden problems like the flawed
mirror hobbling its more famous space telescope cousin, officials say.
The second in a series of ``great observatories'' expected to
revolutionize humanity's knowledge of the cosmos, the $550 million Gamma
Ray Observatory is scheduled for launch aboard the space shuttle
Atlantis around the end of March or early April.
Unlike the $1.5 billion Hubble Space Telescope, ``GRO'' is not
capable of detecting visible light. Like its name suggests, the
satellite was built to study high-energy gammay rays emitted by the most
violent stars and galaxies in the universe.
By studying such radiation, scientists hope to gain insights into the
processes inside a smorgasbord of celestial objects, including exploding
stars, enigmatic quasars and black holes.
``They (gamma rays) are very penetrating and related to the most
high-enegy processes taking place,'' said project scientist Donald
Kniffen. ``Therefore, they are a very effective probe of high energy
processes in stellar objects in the deepest parts of our galaxy and on
beyond our galaxy.''
The squat 35,000-pound satellite, which fills up half of the
shuttle's 60-foot-long cargo bay, looks like a giant insect when its two
solar panels are unfolded, stretching 70 feet from tip to tip and
generating 2,000 watts of power.
NASA plans to launch GRO into a 280-mile-high orbit tilted 28.5
degrees to the equator.
``We're in the final two months of training,'' shuttle skipper Steven
Nagel said last week. ``It's going very well. We've got a lot of work
ahead of us, but we'll be ready to fly.''
Equipped with four instruments weighing up to 2 tons each, GRO is
expected to spend two years mapping high-energy gamma ray sources across
the entire sky with 10 times the sensitivity of any previous such
satellite. The satellite may be refueled later by a visiting shuttle
crew to extend its mission.
Future great observatories are being built to study X-rays and
infrared radiation from vantage points high above Earth's obscuring
atmosphere, giving astronomers a chance to study the entire
electromagnetic spectrum in unprecedented detail.
The latest phase of America's intellectual assault on the cosmos
began April 25, 1990, when the Hubble Space Telescope was deployed from
the shuttle Discovery.
NASA managers later discovered Hubble's supposedly perfect 94.5-inch
mirror was seriously flawed, preventing the telescope from bringing
starlight to a sharp focus.
Concern about Hubble's trouble prompted additional reviews to make
sure no hidden problems were awaiting the Gamma Ray Observatory. None
was found.
``There is a lot of difference between the Hubble and the GRO in the
way the signals are collected,'' said project manager John Hraster. ``We
don't have a comparable single system, such as the mirror system.''
GRO is not equipped with a mirror for the simple reason that the
particles, or ``photons,'' making up gamma rays are so energetic they
would simply penetrate and pass through any kind of conventional mirror
or lens.
Instead, the Gamma Ray Observatory is equipped with four massive
instruments to record the passage of gamma rays packing various amounts
of energy.
As the gamma rays smash into devices called scintillators, visible
light will be produced that can be studied by various instruments to
learn more about the radiation itself.
Hraster said GRO's four instruments were tested separately and then
all together in separate ``end-to-end tests'' to simulate the
satellite's operation in orbit. The observatory passed with flying
colors and engineers do not anticipate any major problems in orbit.
One of the mysteries of quantum physics is the wave-particle duality
of nature: depending on the instruments used, electromagnetic radiation
can behave like oscillating waves or discrete particles, or photons.
``Gamma rays because of their very high energy nature, really have
more particle-like properties than they do wave-like properties in the
wave-particle duality of nature,'' Kniffen said. ``Therefore, particle-
type detectors are used as opposed to the telescopes that you might be
used to for visible observations.''
The GRO instruments will be used for at least two years, taking up to
two weeks per observation.
``We on the science team of the Gamma Ray Observatory are very
excited about what we know we're going to be able to see based on
previous missions and theoretical analysis,'' Kniffen said.
``With such a tremendous increase in observing capability ... it's
the unexpected that really adds to the excitement. So we're all eagerly
anticipating the launch and many, many exciting results coming from the
mission.''
|
| 636.6 | GRO Status Report - February 8, 1991 | PRAGMA::GRIFFIN | Dave Griffin | Fri Feb 08 1991 19:20 | 35 |
| From: [email protected] (Peter E. Yee)
Date: 8 Feb 91 19:28:13 GMT
Organization: NASA Ames Research Center, Moffett Field, CA
GRO Status Report
Kennedy Space Center
February 8, 1991
George Diller
407/867-2468
FTS 823-2468
GAMMA RAY OBSERVATORY/STS-37 (Atlantis-April, 1991)
The Gamma Ray Observatory began its 1-mile trip from the
Payload Hazardous Servicing Facility to the Vertical Processing
Facility (VPF) at 5:00 a.m. Thursday morning as scheduled. It
arrived at the VPF air lock about one hour later and was moved
into the high bay at 8:30 a.m. Work was completed by early
afternoon to remove the protective covers and the anti-static
liner over the spacecraft. Preparations are being made today for
hoisting the Observatory into the west test cell. The actual
crane operation is scheduled for Saturday morning.
Next week, on Feb. 12 a two-day stand alone Observatory
functional test will be conducted. The following week the
integrated electrical tests are scheudled to start, beginning
with the Interface Verification Test on Feb. 19 to verify the
GRO's electrical compatability with the orbiter. The end-to-end
test will follow on approximately Feb. 21 to verify
communications between the Observatory and the Payload Operations
Control Center at Goddard. The payload will go to the pad on or
about Mar. 6.
|
| 636.7 | GRO Activity Report - 3/12/91 | PRAGMA::GRIFFIN | Dave Griffin | Tue Mar 12 1991 18:20 | 61 |
| From: [email protected] (Ron Baalke)
Date: 12 Mar 91 15:47:33 GMT
Organization: Jet Propulsion Laboratory, Pasadena, CA.
PAYLOAD TEST AND ACTIVITY SHEET
Kennedy Space Center, Florida
March 12, 1991
George Diller
407/867-2468
FTS 823-2468
GAMMA RAY OBSERVATORY
STS-37/Atlantis
HISTORICAL ACTIVITY
Arrival of Spacecraft at PHSF: 2/6/90
First functional test begins: 2/26
Install High Gain Antenna: 11/8
Final functional test complete: 12/4/90
Spacecraft Fueling complete: 1/11/91
Install Flight Batteries: 1/15
Airborne Electrical Support Equipment (AESE) arrives: 1/24
Install orbiter Airborne Electrical Support Equipment (AESE): 2/1
Transfer GRO to Vertical Processing Facility: 2/7
Installation into west test cell: 2/9
VPF Standalone Functional Test: 2/12-13
Interface Verification Test (IVT) of AESE: 2/17
IVT of GRO (orbiter interfaces simulated): 2/23
End-to-End (ETE) communications test (MILA/GSFC/TDRS): 2/25
Payload Readiness Review: 2/25
MILA RF communications test: 3/4
Transfer payload to canister: 3/11
ACTIVITY FORECAST * denotes change
Roll to Pad 39-B/Transfer to PCR: 3/13*
Initial GRO Battery Charging: 3/14*
Payload installation into Atlantis: 3/17*
TCDT: 3/19-20*
Astronaut payload bay walk down: 3/19
Interface Verification Test: 3/21*
Launch Readiness Review: 3/21
GRO/orbiter end-to-end test: 3/25*
Battery reconditioning: 3/25-30*
GRO Flight Closeout operations: 4/1*
Close payload bay doors: 4/2*
end
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |___ M/S 301-355 | Change is constant.
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 |
|_____|/ |_|/ |_____|/ |
|
| 636.8 | Gamma Ray Observatory ready for launch--last milestone reached | PRAGMA::GRIFFIN | Dave Griffin | Thu Apr 04 1991 19:31 | 69 |
| From: [email protected] (Peter E. Yee)
Date: 4 Apr 91 19:14:55 GMT
Organization: NASA Ames Research Center, Moffett Field, CA
George Diller April 3, 1991
Kennedy Space Center
407/867-2468
KSC Release No. 42-91
GAMMA RAY OBSERVATORY READY FOR LAUNCH--LAST MILESTONE REACHED
The payload bay doors of the Space Shuttle Atlantis were
closed for flight at 9:50 A.M. on Tuesday, April 2, concluding
over 15 months of testing and prelaunch preparation of the Gamma
Ray Observatory (GRO) by the NASA/TRW payload test team.
GRO arrived at the Kennedy Space Center on February 6, 1990,
and was placed in the Payload Hazardous Servicing Facility (PHSF)
located in the KSC Industrial Area where final assembly, fueling,
and functional testing were performed. The spacecraft was loaded
with 4,200 gallons of hydrazine propellant, the largest quantity
ever to be loaded aboard a satellite.
With the remanifesting of Space Shuttle flights during 1990
because of the hydrogen leak difficulty, NASA and TRW management
took advantage of having additional time to study each of the
problems on the Hubble Space Telescope to determine whether they
might also apply to the Gamma Ray Observatory. The test team
researched engineering specifications and historical test data in
search of any problems which may have gone undetected. In
addition, more contingency planning was done based on the Hubble
experience.
By the time GRO was ready to be moved to the Vertical
Processing Facility (VPF) for its integrated testing, the team
was confident they would not have similar problems and that
indeed every system on the Observatory was functioning as
designed.
The astronauts also had an opportunity to inspect GRO at the
conclusion of its testing in the PHSF.
On February 7, 1991, a year and a day after the spacecraft
arrived at KSC, it was moved to the VPF to begin checkout of its
Space Shuttle interfaces. The NASA/McDonnell Douglas team at KSC
verified that all was in readiness, and that associated
communications links were operating. On March 13, the Gamma Ray
Observatory was moved to the launch pad, and loaded aboard the
Space Shuttle Atlantis four days later.
While GRO fills only half of the payload bay of Atlantis, it
weighs in at 34,493 pounds, the heaviest satellite to be deployed
by the Space Shuttle into low Earth orbit.
After interface checks and a brief functional test, followed
by a final communications checkout, the flight batteries were
reconditioned and a trickle charge established. Removing the
trickle charge and reading the battery voltages are the last
items on the checklist before commiting GRO to launch. This
operation occurs 50 minutes before the liftoff.
"With the payload bay doors closed, we've reached a point
we've been anticipating for a long, long time," said Observatory
Manager Marty Davis from the Goddard Space Flight Center.
"There's no remaining work to be done. Now its just the anxious
wait."
|
| 636.9 | Since when did they start measuring hydrazine in gallons? | PRAGMA::GRIFFIN | Dave Griffin | Thu Apr 04 1991 19:35 | 6 |
| > with 4,200 gallons of hydrazine propellant, the largest quantity
> ever to be loaded aboard a satellite.
I think this is a slip. It's supposed to be pounds.
- dave
|
| 636.10 | Payload Summary for 04/03/91 | PRAGMA::GRIFFIN | Dave Griffin | Thu Apr 04 1991 19:40 | 50 |
| From: [email protected] (Peter E. Yee)
Date: 4 Apr 91 19:12:30 GMT
Organization: NASA Ames Research Center, Moffett Field, CA
PAYLOAD TEST AND ACTIVITY SHEET
Kennedy Space Center, Florida
April 3, 1991
George Diller
407/867-2468
FTS 823-2468
GAMMA RAY OBSERVATORY
STS-37/Atlantis
HISTORICAL SUMMARY
Arrival of Spacecraft at PHSF: 2/6/90
First functional test begins: 2/26
Install High Gain Antenna: 11/8
Final functional test complete: 12/4/90
Spacecraft Fueling complete: 1/11/91
Install Flight Batteries: 1/15
First Joint Integrated Simulation (JIS): 1/16
Airborne Electrical Support Equipment (AESE) arrives at VPF: 1/24
Astronaut payload sharp edge inspection: 1/29
Install orbiter Airborne Electrical Support Equipment (AESE): 2/1
Transfer GRO to Vertical Processing Facility: 2/7
Installation into VPF west test cell: 2/9
VPF Stand-alone Functional Test: 2/12-13
Interface Verification Test (IVT) of AESE: 2/17
IVT of GRO (orbiter interfaces simulated): 2/22
End-to-end (ETE) communications test (MILA/GSFC/TDRS): 2/25
Payload Readiness Review: 2/25
MILA RF communications test: 3/4
Transfer payload to canister: 3/11
Roll to Pad 39-B/Transfer to PCR: 3/13
Initial GRO Battery Charging: 3/13
Payload installation into Atlantis: 3/17
Astronaut payload bay sharp edge inspection: 3/19
Interface Verification Test (IVT): 3/21
GRO end-to-end test: 3/25
Battery reconditioning: 3/25-3/30
Final JIS-Nominal Day 3 deploy: 3/27
GRO final closeouts for flight: 4/1
Close payload bay doors: 4/2
|
| 636.11 | Gamma Ray Observatory State Vectors/Keplarian Elements 4/8/91 | PRAGMA::GRIFFIN | Dave Griffin | Tue Apr 09 1991 19:30 | 28 |
| Gamma Ray Observatory State Vectors/Keplarian Elements 4/8/91
Gamma Ray Observatory Vector
Liftoff Time: 1991:095:14:22:44.952
Liftoff Date: 4/5/91
Vector Time (GMT) : 098:06:22:44.952
Vector Time (MET) : 002:16:00:00.000
Orbit Count : 42
Weight : 34442 LBS
Drag Coefficient : 2.0
Drag Area: 502.7 SQ FT
M50 Elements Keplerian Elements
----------------------- --------------------------
X = 17784338.2 FT A = 3689.4166 NM
Y = -9313151.3 FT E = 0.000481
Z = 9960718.3 FT I (M50) = 28.30452 DEG
Xdot = 13256.152549 FT/S Wp (M50) = 59.15065 DEG
Ydot = 20868.092042 FT/S RAAN (M50) = 219.47854 DEG
Zdot = -4135.596178 FT/S / N = 51.23345 DEG
Anomalies \ M = 51.19046 DEG
HA = 244.891 NMI
HP = 240.646 NMI
|
| 636.12 | GRO Status Report #8 - 04/15/91 | PRAGMA::GRIFFIN | Dave Griffin | Mon Apr 15 1991 20:28 | 96 |
| GRO Status Report #8
GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #8
April 15, 1991, 9:00 a.m.
CURRENT STATUS OF OBSERVATORY:
o The Goddard Space Flight Center Payload Operation Control
Center reports that the Gamma Ray Observatory (GRO) is in its
normal pointing mode with solar arrays oriented towards the Sun.
o GRO is in orbit at an altitude of 287 x 280 statute miles (462
x 451 kilometers).
DEVELOPMENTS SINCE STATUS REPORT #7:
o Friday, controllers successfully commanded the spacecraft to
perform two maneuvers in the pitch axis. First, GRO was pitched
down 30 degrees, within the fine Sun sensor's limits then GRO was
pitched down an additional 30 degrees to evaluate operation
outside the normal fine Sun sensor limits. Both of the
spacecraft's fine Sun sensors checked out within specifications,
as expected.
o This weekend, controllers compared the observatory's two fixed
head star trackers. The star trackers were trained on the same
star field so that their accuracy could be evaluated. Both
star trackers have worked well independently in supporting the
various attitude pointing modes and this weekend's test verifies
that they are both in agreement.
SUBSYSTEMS / INSTRUMENT STATUS:
COMMUNICATIONS AND DATA HANDLING:
o Command and telemetry links with the spacecraft remain
excellent.
POWER:
o Spacecraft batteries are charged at 100 percent and working
well.
ATTITUDE AND CONTROL DETERMINATION:
o GRO has returned to a normal pointing mode.
THERMAL:
o Temperature sensors indicate nominal readings.
PROPULSION:
o System is stable.
o A review team will meet tomorrow, Tuesday, April 16, 1991 at
the Goddard Space Flight Center to investigate the tank one
pressure transducer and the valve mis-configuration anomalies. No
impact on the mission is seen by these anomalies at this time.
INSTRUMENTS:
o All instrument heaters are on.
o Instrument low-voltage turn-on begins today.
o Turn-on runs through tomorrow (April 16, 1991) will resumes on
Thursday, April 18 and Friday, April 19.
o Instrument turn-on still scheduled to be completed no earlier
than April 29, as planned.
o Instrument calibration begins no earlier than April 29 to be
completed no earlier than May 14, as planned.
o Science operations of the observatory begins no earlier
than May 15, 1991.
UPCOMING EVENTS:
o Controllers initially planned to test the B-side attitude
control electronics today, however, a determination was made to
run the controllers through the maneuver on the GRO simulator
before attempting the change-over from the A-side attitude
control electronics to the B-side attitude control electronics on
the spacecraft.
o The B-side attitude control electronics check will be done on
Wednesday, April 17, 1991.
o Instrument turn-on will begin today, be suspended during B-side
electronics check-out, and resume on Thursday, April 18, 1991.
|
| 636.13 | GRO Status Reports #1-4 (back issues) | PRAGMA::GRIFFIN | Dave Griffin | Wed Apr 17 1991 18:32 | 278 |
| GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #1
April 6, 1991, 3:00 p.m.
CURRENT STATUS OF OBSERVATORY:
The check-outs of the Gamma Ray Observatory (GRO) to date
show the observatory is in excellent shape.
The in-bay functional test, (a check-out of GRO while it
remains in the shuttle's payload bay), began at 6:39 a.m. EST,
Saturday morning, April 6. The GRO team stepped through the
planned GRO check-list, and all functions were nominal. The
results of the subsystem/instrument test follow:
COMMUNICATIONS AND DATA HANDLING SYSTEM:
The transmitters are working fine. The direct link between GRO and
TDRSS (Tracking and Data Relay Satellite System) was successful and
the link should function well after deployment.
POWER: The batteries were on-line for the battery test, and the
state-of-charge remains 100%.
ATTITUDE AND CONTROL DETERMINATION:
The gyros were operating nominally and were tracking the rate of
motion of the orbiter. All four reaction wheels (used to control
the attitude of GRO) checked out. (Once turned in one direction
they turned GRO in the opposite direction.)
THERMAL:
Temperatures on GRO are nominal. The Airborne Electrical Support
Equipment, which gets electrical power from the shuttle and powers
heaters on GRO, was turned on when the payload bay doors were
opened after launch. All temperatures were nominal and the
parameters remained nominal as they were monitored throughout
Friday night and Saturday.
PROPULSION:
Pressures and temperatures are as they should be.
INSTRUMENTS:
A visual check by the shuttle's television cameras shows all four
instruments are in good mechanical condition. The instruments will
be turned on within the next two weeks.
UPCOMING EVENTS:
GRO will remain in a passive mode until deployment activities begin
Sunday morning, April 7, at 5:53 a.m. EDT. Deployment should be
completed within 10 hours, after which GRO should be a free flyer.
###
GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #2 April 7, 1991, 8:00
p.m. EST
CURRENT STATUS OF OBSERVATORY:
After release from the Space Shuttle Atlantis, the Gamma Ray
Observatory (GRO) took control and went into a Sun reference
pointing mode (pointing toward the Sun) and convergence to a stable
condition in that mode is taking place now.
DEVELOPMENTS SINCE LAST STATUS REPORT:
GRO deployment procedures were nominal through the deployment of
the solar arrays.
The high gain antenna deployment proceeded well until the command
was given to deploy. After a series of contingency operations
failed to release the antenna, an Extra Vehicular Activity (EVA),
that was a planned contingency, was executed by Astronauts Jerry
Ross and Jay Apt. Ross shook the antenna boom laterally, which
broke it free from the obstruction. Based on this success, the
decision was made to perform the rest of the deployment with Ross
handcranking the antenna to full extension. Preliminary findings
indicate that the obstruction may have been caused by the thermal
blanket on the boom becoming caught on the latch mechanism.
Once the antenna was freed and deployed by the astronaut the
remainder of the spacecraft testing was completed prior to release
at MET 2/8:15 or 6:37 p.m. EDT.
COMMUNICATIONS AND DATA HANDLING SYSTEM:
All equipment is working well. A direct link test between GRO and
TDRSS (Tracking and Data Relay Satellite System), conducted while
GRO was in the payload bay, was successful.
POWER: The state-of-charge of the batteries is 100%. Full power
output from the solar arrays was received.
ATTITUDE AND CONTROL DETERMINATION: All sensors are operating
properly. The High Gain Antenna's azimuth and elevation (movement
up and down and sideways) works properly.
THERMAL: All temperatures appear normal.
PROPULSION: All pressures and temperatures look good. The anomoly,
which has not been repeated, on one heater circuit is under
investigation.
INSTRUMENTS: Indications from housekeeping data (temperature,
pressure, etc.) are all nominal. The instruments will be turned on
within the next two weeks.
UPCOMING EVENTS: Spacecraft checkouts have commenced and will
continue 24 hours daily for several days.
###
GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #3 April 8, 1991, 1:00
p.m.
CURRENT STATUS OF OBSERVATORY: The Gamma Ray Observatory (GRO) is
stable in the Sun reference pointing mode (SRPM), pointing towards
the Sun, controlled by the control processing electronics (CPE)
computer system. GRO's altitude is 462x451 kilometers
(approximately 249 nautical miles above Earth).
DEVELOPMENTS SINCE LAST STATUS REPORT: All stars were found in the
star trackers (sensors that look for stars and provide information
that is used to determine the attitude of the observatory). The
observatory communicated successfully with the Tracking and Data
Relay Satellite System (TDRSS) through the High Gain Antenna (HGA).
There is no evidence of damage to the HGA from the Extravehicular
Activity (EVA). Tape recorder data was transmitted successfully to
the data collection center at Goddard Space Flight Center,
Greenbelt, MD.
COMMUNICATIONS AND DATA HANDLING SYSTEM: The direct link of the
high gain antenna with TDRSS is working well. Transmission of 512
kps (kilobits per second) data dump to Goddard was completed.
POWER: State-of-charge of the batteries is 100%. Abundant power is
available from the solar arrays. The power loads on the two
modular power systems (MPS) on both sides of the spacecraft are
well balanced.
ATTITUDE AND CONTROL DETERMINATION: The control processing
electronics computer system is keeping the observatory in the Sun
reference pointing mode successfully. All sensors are normal. The
fixed head star trackers (FHST) have all the appropriate stars in
their fields of view.
THERMAL: Nominal.
PROPULSION: Tank 1 pressure transducer (measuring device) shows an
apparent malfunction. However, temperature of the tank is normal.
The cause of this anomaly is being investigated; the success of the
mission will not be affected by the transducer problem.
There was an anomaly when commands were given to the isolation
valves (valves in the propulsion system that isolate the thrusters)
in the propulsion system. The problem is under investigation.
Certain thruster modes will not be used until the isolation valve
anomaly is better understood.
A temporary problem, a temperature higher than expected on one
heater circuit on the Orbit Adjust Thruster 2, that occurred
yesterday has not recurred. The heater is operating normally now.
A temporary partial short may have caused the problem.
INSTRUMENTS: Burst and Transient Source Experiment (BATSE);
Oriented Scintillation Spectrometer Experiment (OSSE); and
Energetic Gamma Ray Experiment Telescope (EGRET): all three
instruments are off; their heaters are on.
The Imaging Compton Telescope (COMPTEL) is off; the heat pipe (a
device to transfer heat from one point to another) is working well
and controlled by the on board computer (OBC).
UPCOMING EVENTS: The Sun reference pointing mode aboard GRO will be
controlled by the on board computer, changing from the controlled
processing electronics computer. If time allows GRO will go to the
sequence of normal maneuver mode, then to normal pointing mode on
the OBC.
Instrument turn-on is expected to begin about April 17 and will be
completed about April 26. Science data will start being acquired
about April 19.
###
GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #4 April 9, 1990, 9:00
a.m.
CURRENT STATUS OF OBSERVATORY: Technicians at the Goddard Space
Flight Center, Payload Operation Control Center are currently
concentrating on tests of the spacecraft pointing systems, and data
handling systems. The spacecraft appears healthy and nominal, at
an altitude of 462 x 451 kilometers (approximately 285 statute
miles).
DEVELOPMENTS SINCE STATUS REPORT #3:
o Command switched from Sun reference pointing mode on the control
processing computer system to the same mode in on-board computers,
successfully.
o On-board computer switched successfully to normal pointing mode.
o On-board computer performed 2 degree normal calibration maneuver,
successfully.
o Spacecraft then returned to normal pointing mode, as planned.
COMMUNICATIONS AND DATA HANDLING:
o Switch made from low gain to high gain antenna, successfully.
o Tape recorder data dumps have been successfully performed.
o Command link tested and operating well.
POWER:
o Batteries are at 100% state-of-charge and looking good.
ATTITUDE AND CONTROL DETERMINATION:
o Performance ten times better than expected.
o Expected accuracy to within .5 degrees, observed accuracy is from
.014 degrees to .022 degrees.
THERMAL:
o Temperature sensors indicating nominal readings.
PROPULSION:
o Technicians developing plans to troubleshoot transducer and valve
anomaly today.
o Yesterday, there was an indication that propellent tank one
pressure transducer had malfunctioned. Since the temperature is
nominal this problem has no impact on mission.
o Also yesterday, an anomaly surfaced in commanding the valves that
isolate the flow of propellent to the spacecraft's thruster. Some
thruster modes will not be used until the cause is known. No
impact on mission is seen by this anomaly at this time.
INSTRUMENTS:
o All instruments are switched off.
o Instrument heaters are on and functioning normally.
o Instrument turn-on slated to begin no earlier than April 17,
completed no earlier than April 29, as planned.
o Instrument calibration to begin no earlier than April 29 will be
completed no earlier than May 14, as planned.
UPCOMING EVENTS:
o Further checkouts of the pointing system are planned.
o Two 90 degree rolls of the spacecraft are to be commanded from
the ground.
o Communications at higher and lower rates will be done to further
test the communications systems.
o Science observations to start no earlier than May 15, 1991.
-end-
|
| 636.14 | GRO Status Reports #5-7 (back issues) | PRAGMA::GRIFFIN | Dave Griffin | Wed Apr 17 1991 18:35 | 243 |
| GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #5 April 10, 1991, 11:30
a.m.
CURRENT STATUS OF OBSERVATORY:
o The Goddard Space Flight Center Payload Operation Control Center
reports all systems operating nominally or better (except for the
two propulsion system anomalies discussed below).
o GRO is in its normal pointing mode with solar arrays indexed to
the Sun.
DEVELOPMENTS SINCE STATUS REPORT #4:
o As part of the mission plan, the spacecraft was rolled 180
degrees around its x-axis in two steps. The first step was a roll
of 60 degrees, the second step was a roll of an additional 120
degrees.
COMMUNICATIONS AND DATA HANDLING:
o There were good command and telemetry links both during and after
the 180 degree roll maneuvers.
o Missed communications on two passes because of temporary
difficulty with TDRS East. This did not affect operations.
POWER:
o Spacecraft batteries are charged at 100 percent and working well.
ATTITUDE AND CONTROL DETERMINATION:
o The 180 degree roll maneuver worked as planned. Performance in
pitch and yaw was excellent.
THERMAL:
o Temperature sensors indicate nominal readings.
PROPULSION:
o System is stable.
o Goddard is forming a review team which will meet next week to
investigate the tank one transducer (measuring device) and valve
misconfiguration anomalies. No impact on the mission is seen by
these anomalies at this time.
INSTRUMENTS:
o All instruments are switched off.
o All instrument heaters are on.
o The OSSE project was provided telemetry in the science format in
order to look at pointing data.
o Instrument turn-on still scheduled to begin no earlier than April
17 and be completed no earlier than April 29, as planned.
o Instrument calibration to begin no earlier than April 29 to be
completed no earlier than May 14, as planned.
UPCOMING EVENTS:
o Additional calibration maneuvers. Today, there will be a yaw
maneuver around the z-axis of approximately 90 degrees.
###
GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #6 April 11, 1991, 9:00
a.m.
CURRENT STATUS OF OBSERVATORY:
o The Goddard Space Flight Center Payload Operation Control Center
reports the Gamma Ray Observatory (GRO) is in its normal pointing
mode with solar arrays indexed to the Sun.
o The spacecraft is holding a 28 degree yaw (Z-axis) induced by
controllers yesterday.
o GRO is in orbit at an altitude of 287 x 280 statute miles (462 x
451 kilometers).
DEVELOPMENTS SINCE STATUS REPORT #5:
o As part of the mission plan, the spacecraft was yawed to 28
degrees. It exceeded the commanded yaw by 2 degrees to 30 degrees.
GRO was corrected back to 28 degrees by controllers. Controllers
will use this information, as planned, to adjust the torque limits
of the spacecraft. The spacecraft reacted as designed.
COMMUNICATIONS AND DATA HANDLING:
o There were good command and telemetry links both during and after
the yaw maneuvers.
o Special communications tests with Atlantis revealed GRO
transmissions caused interference with normal space shuttle
communications. Communication frequencies of the orbiter and the
GRO are very close causing this interference. Technicians expected
this problem and no mission impact is expected.
POWER:
o Spacecraft batteries are charged at 100 percent and working well.
ATTITUDE AND CONTROL DETERMINATION:
o The 28 degree yaw maneuver worked well.
THERMAL:
o Temperature sensors indicate nominal readings.
PROPULSION:
o System is stable.
o Goddard is forming a review team which will meet Tuesday, April
16, 1991 at the Goddard Space Flight Center to investigate the tank
one pressure transducer and valve misconfiguration anomalies. No
impact on the mission is seen by these anomalies at this time.
INSTRUMENTS:
o All instruments are switched off.
o All instrument heaters are on.
o Instrument turn-on still scheduled to begin no earlier than April
17 and be completed no earlier than April 29, as planned.
o Instrument calibration to begin no earlier than April 29 to be
completed no earlier than May 14, as planned.
UPCOMING EVENTS:
o Today controllers will maneuver the spacecraft back to normal
pointing in the yaw axis. Two maneuvers in the pitch axis will
then be performed. First, GRO will pitch down 30 degrees, within
the fine Sun sensor's limits then another 30 degrees to exceed
limits to test the fine Sun sensor.
###
GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #7 April 12, 1991, 9:00
a.m.
CURRENT STATUS OF OBSERVATORY:
o The Goddard Space Flight Center Payload Operation Control Center
reports the Gamma Ray Observatory (GRO) is in its normal pointing
mode with solar arrays oriented towards the Sun.
o GRO is in orbit at an altitude of 287 x 280 statute miles (462 x
451 kilometers).
DEVELOPMENTS SINCE STATUS REPORT #6:
o Controllers removed the reaction wheel torque limits, believed
to be the cause of yesterday's nearly 3 degree overshoot. This
overshoot occurred in the yaw axis. When the spacecraft was
commanded to yaw 28 degrees, it overshot to just over 30 degrees.
GRO self-corrected back to 28 degrees, as designed. Controllers
then removed the reaction wheel torque limits and re-commanded the
28 degrees yaw. The overshoot was reduced from just under 3
degrees to 0.13 degrees. This is well within limits. The
spacecraft reacted as designed.
o This test verifies the yaw gyro alignment.
SUBSYSTEMS / INSTRUMENT STATUS:
COMMUNICATIONS AND DATA HANDLING:
o Command and telemetry links with the spacecraft remain excellent.
o Controllers successfully demonstrated simultaneous communication
using the Tracking and Data Relay Satellite System. GRO received
commands from the Tracking and Data Relay Satellite (TDRS) East
while simultaneously relaying telemetry to Earth via TDRS West.
POWER:
o Spacecraft batteries are charged at 100 percent and working well.
ATTITUDE AND CONTROL DETERMINATION:
o GRO has returned to normal pointing from the 28 degrees yaw
maneuver.
THERMAL:
o Temperature sensors indicate nominal readings.
PROPULSION:
o System is stable.
o Controllers have taken steps to ensure GRO receives no propulsion
commands until the tank one pressure transducer and valve
misconfiguration anomalies are fully understood. Goddard has
formed a review team which will meet Tuesday, April 16, 1991 at the
Goddard Space Flight Center to investigate the anomalies. No
impact on the mission is seen by these anomalies at this time.
INSTRUMENTS:
o All instruments are switched off.
o All instrument heaters are on.
o Instrument turn-on still scheduled to begin no earlier than April
17 and be completed no earlier than April 29, as planned.
o Instrument calibration to begin no earlier than April 29 to be
completed no earlier than May 14, as planned.
o Science operations of the observatory are to begin no earlier
than May 15, 1991
UPCOMING EVENTS:
o Today controllers will command the spacecraft to perform two
maneuvers in the pitch axis. First, GRO will pitch down 30
degrees, within the fine Sun sensor's limits then GRO will pitch
down an additional 30 degrees to evaluate operation outside the
normal fine Sun sensor limits.
o This weekend, controllers plan to compare the observatory's two
f
|
| 636.15 | GRO Status Report #9 - 04/16/91 | PRAGMA::GRIFFIN | Dave Griffin | Wed Apr 17 1991 18:43 | 81 |
| GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #9
April 16, 1991, 9:00 a.m.
CURRENT STATUS OF OBSERVATORY:
o The Goddard Space Flight Center Payload Operation Control
Center reports that the Gamma Ray Observatory (GRO) is in its normal
pointing mode with solar arrays oriented towards the Sun.
o GRO is in orbit at an altitude of 287 x 280 statute miles (462 x
451 kilometers).
DEVELOPMENTS SINCE STATUS REPORT #8:
o Instrument turn-on began yesterday, will be suspended during
B-side electronics check-out on Wednesday, and resumes on Thursday,
April 18, 1991.
o At 11:29 a.m. EDT, yesterday, the Oriented Scintillation
Spectrometer Experiment (OSSE) successfully detected the charged
particles of the South Atlantic anomaly during Orbit 156. This is a
positive indication that OSSE is alive and well.
o Controllers initially planned to test the B-side attitude control
electronics yesterday, however, a determination was made to run the
controllers through the maneuver on the GRO simulator before
attempting the changeover from the A-side attitude control
electronics to the B-side attitude control electronics on the
spacecraft.
COMMUNICATIONS AND DATA HANDLING:
o Command and telemetry links with the spacecraft remain excellent.
POWER:
o Spacecraft batteries are charged at 100 percent and working well.
ATTITUDE AND CONTROL DETERMINATION:
o GRO is in a normal pointing mode.
THERMAL:
o Temperature sensors indicate nominal readings.
PROPULSION:
o System is stable.
o The first meeting of the review team, formed to investigate the
tank one pressure transducer and the valve mis-configuration
anomalies, takes place today at 1:00 p.m. EDT at the Goddard Space
Flight Center, Greenbelt, Md. No impact on the mission is seen by
these anomalies at this time.
INSTRUMENTS:
o All instrument heaters are on.
o Instrument turn-on began yesterday.
o Turn-on runs through today and resumes on Thursday, April 18 and
Friday, April 19.
o Completetion of Instrument turn-on still scheduled to be for no
earlier than April 29, as planned.
o Instrument calibration begins no earlier than April 29 to be
completed no earlier than May 14, as planned.
o Science operations of the observatory begins no earlier than May
15, 1991.
UPCOMING EVENTS:
o The B-side attitude control electronics check will be done on
Wednesday, April 17, 1991.
o Instrument turn-on continues.
|
| 636.16 | GRO Status Report #10 - 04/17/91 | PRAGMA::GRIFFIN | Dave Griffin | Wed Apr 17 1991 18:48 | 82 |
| GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #10
April 17, 1991, 9:00 a.m.
CURRENT STATUS OF OBSERVATORY:
o The Goddard Space Flight Center Payload Operation Control
Center reports that the Gamma Ray Observatory (GRO) is in its
normal pointing mode with solar arrays oriented towards the Sun.
o GRO is in orbit at an altitude of 287 x 280 statute miles (462
x 451 kilometers).
DEVELOPMENTS SINCE STATUS REPORT #9:
o All four instruments were activated yesterday with low voltage.
o Controllers activated the Burst and Transient Source Experiment
(BATSE) with high voltage yesterday afternoon.
o At 11:30 p.m. EDT, last night, both the Oriented Scintillation
Spectrometer Experiment (OSSE) and the Burst and Transient Source
Experiment (BATSE) detected a solar flare. This is a very
positive indication that both BATSE and OSSE are functioning
well.
COMMUNICATIONS AND DATA HANDLING:
o Command and telemetry links with the spacecraft remain
excellent.
POWER:
o The spacecraft solar array performance is better than expected
and the batteries are charged at 100 percent and working well.
ATTITUDE AND CONTROL DETERMINATION:
o GRO continues in a normal pointing mode.
THERMAL:
o Temperature sensors indicate nominal readings.
PROPULSION:
o System is stable.
o The members of the review team, formed to investigate the tank
one pressure transducer and the valve mis-configuration
anomalies, met yesterday. Propulsion system technical experts
presented the chronology of events that occurred during
propulsion system activation. The review is continuing today. No
impact on the mission is seen by these anomalies at this time.
INSTRUMENTS:
o All instrument heaters are on.
o All instrument low-voltage power supplies are on.
o High-voltage turn-on runs through today and resumes on
Thursday, April 18, and Friday, April 19.
o Instrument turn-on still scheduled to be completed no earlier
than April 29, as planned.
o Instrument calibration begins no earlier than April 29 to be
completed no earlier than May 14, as planned.
o Science operations of the observatory begins no earlier
than May 15, 1991.
UPCOMING EVENTS:
o The B-side attitude control electronics check has been re-
scheduled so that more time can be devoted to refining
procedures.
o Instrument high-voltage turn-on continues.
|
| 636.17 | In case you were wondering... | PRAGMA::GRIFFIN | Dave Griffin | Wed Apr 17 1991 18:53 | 14 |
| I won't be posting these every day for the next few months or anything.
The first week or two of activities starting up a major space observatory is,
to me - and I expect others, fascinating. So I thought I'd post the
reports here.
If the volume of the reports doesn't die down soon, I'll either resort to
weekly summary postings with the daily reports available as files in the
pragma space "archives".
If you have opinions on this either way, I'd be interested in them. Drop
me a mail message.
- dave
|
| 636.18 | GRO Status Report #11 - 04/18/91 | PRAGMA::GRIFFIN | Dave Griffin | Thu Apr 18 1991 19:35 | 86 |
| GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #11
April 18, 1991, 9:00 a.m.
CURRENT STATUS OF OBSERVATORY:
o The Goddard Space Flight Center Payload Operation Control
Center reports that the Gamma Ray Observatory (GRO) is in its
normal pointing mode with solar arrays oriented towards the Sun.
o GRO is in orbit at an altitude of 287 x 280 statute miles (462
x 451 kilometers).
DEVELOPMENTS SINCE STATUS REPORT #10:
o The Burst and Transient Source Experiment is continuously
operating with high voltage and controllers report all systems
normal.
o The Oriented Scintillation Spectrometer Experiment is
continuously operating with high voltage and controllers report
all systems normal.
o The Energetic Gamma Ray Experiment has completed a partial turn
on of high voltage and will complete high voltage turn-on this
afternoon.
o The Imaging Compton Telescope continues to operate at low
voltage and high voltage is scheduled for turn-on Friday, April
19, 1991.
COMMUNICATIONS AND DATA HANDLING:
o Command and telemetry links with the spacecraft remain
excellent.
o There will be a meeting today at the Goddard Space Flight
Center of a committee formed to investigate the conditions that
led Astronauts Jerry Ross and Jay Apt to perform an emergency
extra-vehicular activity on Sunday, April 7, to free the Gamma
Ray Observatory high-gain antenna.
POWER:
o The spacecraft solar array performance is better than expected
and the batteries are charged at 100 percent and working well.
ATTITUDE AND CONTROL DETERMINATION:
o GRO continues in a normal pointing mode.
THERMAL:
o Temperature sensors indicate nominal readings.
PROPULSION:
o System is stable.
o The members of the review team, formed to investigate the tank
one pressure transducer and the valve mis-configuration
anomalies, met through noon yesterday. Project management is
currently reviewing the recommendations of the committee. The
review is continuing today. No impact on the mission is seen by
these anomalies at this time.
INSTRUMENTS:
o High voltage turn-on continues today.
o Instrument calibration begins no earlier than April 22 to be
completed in early May, as planned.
o Science operations of the observatory begins in early May.
UPCOMING EVENTS:
o The B-side attitude control electronics check has been re-
scheduled to begin at 10:00 a.m. EDT, Sunday, April 21, 1991.
o Instrument high voltage turn-on continues.
|
| 636.19 | GRO Status Report #12 - 04/19/91 | PRAGMA::GRIFFIN | Dave Griffin | Fri Apr 19 1991 19:01 | 70 |
| GAMMA RAY OBSERVATORY (GRO) STATUS REPORT #12
April 19, 1991, 9:00 a.m.
CURRENT STATUS OF OBSERVATORY:
o The Goddard Space Flight Center Payload Operation Control
Center reports that the Gamma Ray Observatory (GRO) is in its
normal pointing mode with solar arrays oriented towards the Sun.
o GRO is in orbit at an altitude of 287 x 280 statute miles (462
x 451 kilometers).
DEVELOPMENTS SINCE STATUS REPORT #11:
o The Burst and Transient Source Experiment (BATSE) is continuously
operating with high voltage and controllers report all systems
normal. BATSE observed its first Gamma Ray Burst at approximately
8:40 a.m. EDT, yesterday, April 18.
o The Oriented Scintillation Spectrometer Experiment is
going through a series of high voltage turn-ons and turn-offs.
o The Energetic Gamma Ray Experiment completed a short high-voltage
turn-on of the spark chamber.
o The Imaging Compton Telescope continues to operate at low
voltage and high voltage is scheduled for turn-on this morning.
The process will continue over a 24-hour period.
COMMUNICATIONS AND DATA HANDLING:
o Command and telemetry links with the spacecraft remain
excellent.
POWER:
o The spacecraft solar array performance is better than expected
and the batteries are charged at 100 percent and working well.
ATTITUDE AND CONTROL DETERMINATION:
o GRO continues in a normal pointing mode.
THERMAL:
o Temperature sensors indicate nominal readings.
PROPULSION:
o System is stable.
o The Project Office is evaluating the information presented by the
GSFC and the TRW investigation team which met on April 16 and April
17. The team was formed to investigate the tank one pressure
transducer and the valve position anomaly.
INSTRUMENTS:
o High voltage turn-on continues today.
o Instrument calibration begins no earlier than April 22 to be
completed in early May, as planned.
o Science operations of the observatory begins in early May.
|
| 636.20 | Posting policy change | PRAGMA::GRIFFIN | Dave Griffin | Fri Apr 19 1991 19:04 | 10 |
| O.K. - I'm switching to newsworthy events only.
Daily status reports (or whatever frequency NASA spits them out) can be
found at:
pragma::public:[nasa.gro]
starting on Monday.
- dave
|
| 636.21 | GRO grabs first target of opportunity | PRAGMA::GRIFFIN | Dave Griffin | Mon Jun 17 1991 10:46 | 50 |
| 6/14/91: GRO SPACECRAFT GRABS FIRST TARGET OF OPPORTUNITY
RELEASE: 91-91
NASA's Gamma Ray Observatory (GRO) was maneuvered to point at its first
scientific target of opportunity, the sun, on Friday, June 7, 1991, at 7:45
p.m. EDT. The 17-ton observatory was repositioned by controllers at the
Goddard Space Flight Center, Greenbelt, Md., to gather data from two X-class
solar flares that occurred on Saturday and Monday nights.
The X-class is the largest and most powerful type of solar flare.
Solar flares are temporary outbursts of intense solar radiation that have been
observed blasting hot loops of gas more than 430,000 miles into space. These
high energy outbursts have been known to disrupt the Earth's magnetic field and
cause interference with communications equipment and electrical power
distribution systems.
While much is known about the composition and magnitude of solar
flares, surprisingly little is known about the thermonuclear processes of these
dynamic solar phenomena. The decision to observe the sun was made by project
scientists and engineers about noon Friday. The flight operations team was able
to complete the maneuver in about nine hours. The normal time for this type of
maneuver is about 36 hours. The fast action of the team gained 23 additional
hours of observing time, allowing GRO to capture data on Saturday's flare which
otherwise would have been lost, officials said.
All four of GRO's instrument teams report that they are receiving good
data on the solar activity, the most sensitive high-energy measurements ever of
the sun. Project Scientist Dr. Neil Gehrels will decide this week whether to
continue solar observations or to move on to the next scheduled target,
Supernova 1991 T, on Thursday, June 14.
The repositioning of GRO demonstrates not only the flexibility of the
spacecraft but also the efficiency of the planned target of opportunity
program, officials explained. This program, they said, allows the scientific
community to position the spacecraft toward significant celestial events that
cannot be predicted. In addition to solar activity, other examples of this
type of event include supernova or other unplanned gamma-ray events.
Science operations for GRO began Thursday, May 16, 1991, with the
observatory pointed toward a pulsar in the Crab Nebula. Science operation plans
call for a full-sky survey expected to last 15 months. GRO was launched on
April 5, 1991, aboard the Space Shuttle Atlantis and deployed on April 7, 1991.
Its mission is to search for highly energetic gamma rays emitted by some of the
most violent processes in the universe.
GRO orbits Earth at an altitude of 287 x 280 statute miles. GRO is
managed and operated by the Goddard Space Flight Center for NASA's Office of
Space Science and Applications.
|
| 636.22 | GRO Status Report - July, 1, 1991 | PRAGMA::GRIFFIN | Dave Griffin | Wed Jul 03 1991 11:18 | 36 |
| GAMMA RAY OBSERVATORY STATUS REPORT
July 1, 1991
The Gamma Ray Observatory (GRO) spacecraft is performing normally. GRO is
in orbit at an altitude of 287 x 280 statute miles (462 x 451
kilometers).
Reports from GRO's instrument sites indicate that all scientific
instruments are receiving data. Currently, the spacecraft is conducting an
all-sky survey which will provide a comprehensive map of all active gamma-ray
sources
On May 27, 1991, the Burst and Transient Source Experiment (BATSE)
scientists, announced that gamma ray bursts are being detected at a higher rate
and in much greater detail than ever before. The sources of these high-powered
bursts of gamma radiation remain unknown.
GRO was maneuvered to point at its first scientific target of
opportunity, the Sun, on Friday, June 7, 1991, at 7:45 p.m. EDT. The purpose
of the maneuver was to gather science data from two X-class solar flares.
Because of this pointing, GRO's instruments made the most sensitive high-
energy measurements ever of the Sun, according to project scientist Dr. Neil
Gehrels of NASAUs Goddard Space Flight Center, Greenbelt, Md.
On June 23, at 2:38 a.m. EDT, controllers at Goddard temporarily lost
up-link communications with the observatory. Thirteen hours of science data
were lost before full communications with GRO were restored. Subsequent tape
recorder playbacks indicate that there are no problems with GRO and nominal
operations have been restored with no further anomalies. Engineers are
studying the problem to isolate the cause of the communications lapse.
Scientific targets planned for July include the galaxy NGC 4151, the
center of our own Milky Way Galaxy and supernova 1987A.
GRO is managed by the Goddard Space Flight Center for NASA's Office of
Space Science and Applications.
|
| 636.23 | NASA Observatory Detects Strongest Gamma Ray Source | PRAGMA::GRIFFIN | Dave Griffin | Thu Jul 25 1991 20:28 | 55 |
| RELEASE: 91-117 (7/25/91)
The Goddard Space Flight Center's Energetic Gamma Ray
Experiment Telescope (EGRET), one of four instruments aboard NASA's
Gamma Ray Observatory (GRO), has detected "the most distant and by far,
the most luminous gamma-ray source ever seen," according to EGRET
Principal Investigator Dr. Carl Fichtel.
The EGRET team, led by Fichtel, reported in a telegram to the
International Astronomical Union, Cambridge, Mass., that a source of
intense localized gamma radiation, was detected between June 15 and 28.
The source of this radiation has been identified with the variable Quasar
3C279, located in the constellation Virgo, approximately 7 billion light
years from Earth.
Fichtel says that the quasar is emitting a large flux of gamma rays,
each gamma ray photon with an energy greater than 100 million electron
volts. In contrast, a visible light photon has an energy of only a few
electron volts, and an x-ray photon has an energy of a thousand electron
volts. The luminosity or total energy emitted by this quasar is
approximately 10 million times that of the total emission of the Milky Way
galaxy, according to the Goddard scientist.
"Quasar 3C279 is a variable quasar, meaning that its intensity changes
over time," Fichtel explained. At its present intensity, this source should
have been visible to two previous gamma ray missions -- NASA's Small
Astronomy Satellite and the European Celestial Observation Satellite. In
the telegram, the EGRET team states that "neither reported a detection
during 1972/73 and 1975-82, respectively."
Summarizing, Fichtel said, "Between 1982 and 1991, this quasar has
gone from being undetectable to being one of the few brightest objects in
the gamma ray sky. Because of its large distance, this observation is
dramatic confirmation of the dynamic nature of the gamma ray sky and an
example of the most energetic processes in nature."
GRO, the second of NASA's Great Observatories, was launched April 5,
1991, aboard the Space Shuttle Atlantis to study high-energy radiation
from deep space.
EGRET is the largest instrument ever assembled in-house by the
Goddard Space Flight Center, Greenbelt, Md. The 7.3 feet by 5.4 feet,
4,001 pound EGRET is between 10 to 20 times larger and more sensitive
than any high-energy gamma-ray telescope ever to orbit the Earth.
Co-principal investigators for EGRET are Dr. Carl Fichtel, Goddard
Space Flight Center, and Dr. Klaus Pinkau, Max Planck Institute, Federal
Republic of Germany. EGRET is the result of a joint effort by scientists
and engineers at Goddard; Stanford University, Calif.; Max Planck
Institute; and Grumman Aerospace Corp., Bethel, N.Y.
The Gamma Ray Observatory was developed, managed and operated
by the Goddard Space Flight Center for NASA's Office of Space Science
and Applications, Washington, D.C.
|
| 636.24 | Gamma Ray Observatory Monthly Status Report - July 29, 1991
| PRAGMA::GRIFFIN | Dave Griffin | Tue Jul 30 1991 13:44 | 32 |
| The Gamma Ray Observatory (GRO) spacecraft and its instruments
are performing normally. GRO is in orbit at an altitude of 273.2
x 279.9 statute miles (450.6 x 439.7 kilometers) and taking
science data.
The Goddard Space Flight Center's Energetic Gamma Ray
Experiment Telescope (EGRET), has detected "the most distant and,
by far, the most luminous gamma-ray source ever seen," according
to EGRET Principal Investigator Dr. Carl Fichtel.
The EGRET team, led by Fichtel, reported that a source of
intense localized gamma radiation, was detected between June 15
and 28. The source of this radiation has been identified with the
variable Quasar 3C279, located in the constellation Virgo,
approximately seven billion light years from Earth.
As of July 23, 1991, the Burst and Transient Source Experiment
(BATSE) scientists, lead by Dr. Gerald J. Fishman, Marshall Space
Flight Center, Huntsville, AL, announced that the instrument has
detected 85 cosmic gamma-ray bursts. This represents a much
higher rate of detection of gamma-ray bursts than had been
thought would occur before the mission. The source of these high-
powered bursts of gamma radiation remains unknown.
Reports from GRO's instrument sites indicate that all
scientific instruments are receiving data and the all-sky survey
to provide a comprehensive map of all active gamma-ray sources is
underway. This survey is expected to be completed by August of
next year.
Upcoming activities for GRO include continued observations of
the center of our galaxy, the Milky Way. Targets that are
planned for August include Super Nova 1987A and the Vela Pulsar.
The Gamma Ray Observatory was managed and operated by the
Goddard Space Flight Center, for NASA's Office of Space Science
and Applications.
|
| 636.25 | Gamma Ray Observatory Monthly Status Report - August 30, 1991 | PRAGMA::GRIFFIN | Dave Griffin | Fri Aug 30 1991 00:09 | 72 |
| The Gamma Ray Observatory (GRO) spacecraft and its instruments
are performing well.
On August 8, 1991, the observatory captured its second target
of opportunity. GRO was pointed towards Cygnus X-3 after radio
astronomers around the world reported an increase in radio
emmisions from this source. Cygnus X-3 is a binary star system,
30,000 light years from Earth, in the disc of our galaxy. GRO's
first target of opportunity, the Sun, was observed June 7, 1991.
Energetic Gamma Ray Experiment Telescope (EGRET) scientists
report that they are engaging in the "lengthy and routine data
analysis phase of scientific discovery," according to Goddard
Project Scientist, Dr. Neil Gehrels. Last month, EGRET detected
"the most distant and, by far, the most luminous gamma-ray source
ever seen," according to EGRET Principal Investigator Dr. Carl
Fichtel, Goddard Space Flight Center, Greenbelt, MD.
As of August 20, 1991, the Burst and Transient Source
Experiment (BATSE) scientists, led by Dr. Gerald J. Fishman,
Marshall Space Flight Center, Huntsville, AL, announced that the
instrument has detected 109 cosmic gamma-ray bursts. This
represents a much higher rate of detection of gamma-ray bursts
than in any previous mission. The source of these high-powered
bursts of gamma radiation remains a mystery.
Reports from GRO's instrument sites indicate that all
scientific instruments are receiving data and that the all-sky
survey which will provide a comprehensive map of active gamma-ray
sources is underway. This survey is expected to be completed by
August 1992.
Upcoming activities for GRO include continued observations of
the Vela Pulsar. Targets that are planned for September include
Hercules X-1 and the Nova Muscae.
The observatory has experienced two minor anomalies during the
month of August, according to project officials at NASA's Goddard
Space Flight Center, Greenbelt, MD.
Goddard's Mission Operation Team reported that on August 17,
1991, at about 11:30 P.M. Eastern Daylight Time (EDT), GRO's
Transponder B locked on to a stray high-powered radio frequency
signal while in orbit over South America. GRO's transponders are
designed to recognize and lock their tuners to signals containing
commands from the Tracking and Data Relay Satellite System
(TDRSS). This signal was from an unknown source and was not
produced by controllers on the ground. As a result of the
transponder lock-out, controllers could not communicate with the
observatory through Transponder B. This lock-out was similar to
two occurrences, one on June 23 and another on July 11.
During the next TDRSS contact the high-gain antenna was
switched to Transponder A and real-time communications were re-
established. A subsequent playback of on-board recorded science
and engineering data indicate that there was no loss of data
associated with this anomaly. GRO engineers are currently
studying the telemetry from these occurrences to isolate a cause.
The second anomaly occurred when the daily stored command list
was uplinked to GRO with incorrect time tags. This command list,
among other functions, contains protective instructions for
passing through the South Atlantic Anomaly -- a region of
electromagnetic disturbances that could damage the observatories
delicate instruments.
The correct command time tags were uplinked during the next
TDRSS pass and no damage to the instruments occured.
The Gamma Ray Observatory is managed and operated by the
Goddard Space Flight Center, for NASA's Office of Space Science
and Applications.
|
| 636.26 | NASA renames Gamma Ray Observatory in honor of Compton | PRAGMA::GRIFFIN | Dave Griffin | Mon Sep 23 1991 14:28 | 45 |
| Michael Braukus
Headquarters, Washington, D.C. September 23, 1991
John Loughlin II
Goddard Space Flight Center, Greenbelt, Md.
RELEASE: 91-151
NASA announced today that the Gamma Ray Observatory, deployed
April 7, 1991, from the Space Shuttle Atlantis, will be renamed in
honor of Nobel Prize-winning American physicist Arthur Holly
Compton. The new official name of the 17-ton orbiting spacecraft
is the Arthur Holly Compton Gamma Ray Observatory or Compton
Observatory.
Currently in an orbit of 273 x 280 statute miles, the Compton
Observatory was designed to study gamma rays, an invisible, high-
energy form of radiation. Its instrumentation is used by
scientists to study gamma-ray sources such as cosmic gamma-ray
bursts, solar flares, supernovae, pulsars, black holes and
quasars.
Dr. Arthur Holly Compton (1892-1962) was the American
physicist whose ground-breaking series of experiments on the
interaction of high-energy radiation and matter demonstrated the
wave/particle duality of nature. His findings played a key role
in the development of modern physics.
In the late 1930s, Compton conducted comprehensive studies of
cosmic rays. Interactions of cosmic rays with interstellar gas
are an important source of the gamma rays that the Compton
Observatory is studying. Compton's work provided significant
clues to our present understanding of many of the basic physical
processes that create gamma radiation.
The Compton Observatory is the second of four planned
spacecraft in NASAs Great Observatories program, including the
Hubble Space Telescope, launched in April 1990, the Advanced X-ray
Astrophysics Facility and the Space Infrared Telescope Facility.
The Compton Observatory is managed by the Goddard Space
Flight Center, Greenbelt, Md. for NASA's Office of Space Science
and Applications.
- end -
|
| 636.27 | Gamma Ray Observatory Postdoctoral Fellowship Program | PRAGMA::GRIFFIN | Dave Griffin | Mon Sep 23 1991 14:29 | 54 |
| The Gamma Ray Observatory (GRO) Fellowship Program, administered by the
National Aeronautics and Space Administration, is intended to provide
scientists of unusual promise and ability opportunities for research on
problems, largely of their own choice, that are related to gamma-ray
astronomy and are compatible with the interests of the host institutions.
Recent postdoctoral scientists (i.e., not more than five years after
doctorate) in Astronomy, Physics and related disciplines are eligible for
this fellowship. The fellow may choose to work at any US research
institution or company involved in GRO or gamma-ray astronomy related
research.
NASA Headquarters will select an independent panel of astronomers to
review all applications, and, based on their recommendations, will choose the
awardees. The GRO Science Support Center located at NASA/Goddard Space
Flight Center will organize the application and selection processes. All
correspondence should be addressed to the Science Support Center.
The duration of a Fellowship will be a total of three years, which
includes an initial period of two years and an extension of another year,
which is granted after a positive midterm review. Fellowships are awarded to
individual postdoctoral scientists and are administered by the host
institutions through a grant assigned to a Staff Scientist at the host
institution. Contingent on funding, up to 4 new GRO Fellows will be awarded
this year.
The detailed Announcement, including the Application Form and
Instructions, is available upon request from:
Gamma Ray Observatory Science Support Center
Fellowship Program
NASA Goddard Space Flight Center
Code 668.1
Greenbelt, Maryland 20771
U.S.A.
It may also be requested by E-mail to any of the following addresses:
GROSSC::GROFELLOW
SPA
(7073::GROFELLOW - until mid September
15765::GROFELLOW - after mid September)
[email protected]
Int
([email protected])
[email protected]
BIT
For further information about the Fellowship Program please contact Dr.
Thomas McGlynn at the GRO Science Support Center (301-286-7780).
The deadline for application receipt is December 16, 1991. Fellows will
be selected by early February 1992. The GRO Fellowship appointments are
expected to begin in the Fall of 1992. Women and minorities are strongly
encouraged to apply. EOE/AAE.
|
| 636.28 | GRO Science Report - October 3 | MTWAIN::KLAES | All the Universe, or nothing! | Tue Oct 08 1991 10:52 | 329 |
| Article: 17336
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Gamma Ray Observatory Science Report
Date: 4 Oct 91 19:11:01 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Given the recent flurry of interest in the GRO BATSE results, I thought
I'd post the latest science reports. Also, many people may not
know that the Gamma Ray Observatory is now officially the
Arthur Holly Compton Gamma Ray Observatory. That's a bit of a mouthful
so I tend just to use Compton Observatory.
Tom McGlynn
Compton Observatory Science Support Center
[email protected]
grossc::mcglynn
--------------------------------------------------------------
Subj: Compton Weekly Report
GRO Science Report #33
Thursday, October 3, 1991
Chris Shrader, COMPTON Science Support Center
Questions or comments can be sent to the GRO SSC. Phone 301/286-7780,
e-mail SPAN GROSSC::SHRADER, Internet [email protected].
MAX '91 Campaign
----------------
During pointing period 11 COMPTON will be oriented with its Z-axis
within 15 degrees of the sun. Since the sun will be accessible to all
of the GRO instruments, providing an excellent capability to measure
hard X-ray, gamma-ray and neutron fluxes from flare emissions, the weeks
of October 3-17 have been designated as the next "FLARES22/MAX91 campaign
interval. For further details, contact Alan Kiplinger (9555::AKIPLINGER)
or Ron Murphy (11335::MURPHY).
Spacecraft Status:
------------------
As of September 25, Compton GRO was in an orbit with an apogee of
446.7 kilometers, perigee of 432.5 kilometers, period of 93.4 minutes,
and inclination of 28.5 degrees. A maneuver to re-point the Z-axis
towards the 3C 273 / 3C279 direction occurred today at 13:09-13:51 UT.
On October 2 at 09:36 UT (5:36 a.m. EDT), the Compton GRO
transponders experienced a high RF signal over Indonesia that
caused receiver A to go into a lockout condition similar to the
situations that occurred on June 23, July 11, and August 18.
Receiver B saw the interfering signal but did not go into the
lockout condition. Previously developed lockout recovery
procedures were used successfully, and recovery was accomplished
before the end of the TDRS contact at 10:30 UT. Since receiver B was
in the normal configuration for real-time operations, there was
NO LOSS of COMMUNICATION with the satellite and NO LOSS of SCIENCE DATA.
UPCOMING EVENTS: After a two-week observation of the Fairall 9
target, COMPTON GRO was maneuved to 3C 273, where the sun will be
accessible to all of the GRO instruments. The current viewing
plan is as follows:
PERIOD MANEUVER DATE +Z AXIS (COMPTEL AND EGRET) TARGET
11 October 3 3C 273
12 October 17 CEN A
13.1 October 31 Galactic Plane 025-14
13.2 November 7 Galactic Plane 339-84 (for GX 339-4 target
of opportunity, 2nd week)
*The complete phase 1 viewing plan is available on GRONEWS.
Other News
----------
The Huntsville Gamma-Ray Burst Workshop will be held on October 16-18.
This meeting should be of great interest, in light of the
major announcements made by the BATSE team at the Second GRO Science
Workshop last week. For more information on where/when read item #1
on GRONEWS. (set host to GROSSC, then log in as "GRONEWS").
There are copies of the abstracts for papers presented at the second
GRO Science Workshop available from the Science Support Center. Send
e-mail requests to GROSSC::BARNES or call us at (301)-286-7780. The
proceedings will unfortunately not be available until the January 1992
time frame.
INSTRUMENT REPORTS:
EGRET
-----
The EGRET operations continue to run smoothly. The instrument performance
remains essentially unchanged. The pointing at the 3C273 and 3C 279
regions begins today. During a portion of this period the instrument
will be operated with the TASC not in coincidence in order to enhance
the low energy sensitivity.
Work on the in-flight calibration study is progressing well as is work
on the calibration and data analysis paper. Analysis of flight data is
being conducted in parallel and is going reasonably well.
BASTE
-----
As of October 1st, BATSE has detected 136 cosmic gamma-ray bursts
out of a total of 739 on-board triggers in 163 days of operation.
There have been 197 triggers due to solar flares with emission above
60 keV.
The x-ray pulsar Vela X-1 appears to been in an active state over the
past week. There have been several periods where pulsations due to
this source are directly visible in the BATSE Large Area Detector
(LAD) rates.
The gain of four of the BATSE Spectroscopy Detectors (SD's) have been
increase in order to enhance their performance at low energies.
In support of Solar observations during the 3C 273 pointing, high
energy resolution spectra will acquired by BATSE at a higher rate.
COMPTEL
-------
Routine operations continue with COMPTEL. The overall instrument performance is
unchanged since the last report. COMPTEL will be participating in the MAX '91
campaign to monitor the Sun for flare emission during the period 3-17 October,
when the Sun will be within COMPTEL's field of view. Upon the repointing of the
spacecraft on 3 October to begin observing period 11, COMPTEL will be enabled to
reconfigure automatically into a solar observing mode immediately upon receipt
of a solar flare trigger from BATSE. The instrument configuration for solar
observations has been improved and optimized, based on experience gained during
the period of the GRO solar target-of-opportunity in June 1991. A large
fraction of the COMPTEL team will be meeting in Holland next week to assess
instrument performance to date, to review all routine data analysis
procedures, and to continue work on initial scientific results from COMPTEL.
OSSE
----
OSSE continues to operate well. For viewing period 11 of Phase I, OSSE will
be observing the quasar 3C 273 as the primary target and the galactic center
region as the secondary target. Observations of the galactic center will be
coordinated with the GRANAT/SIGMA gamma ray mission, and equal viewing
priorities will be given to the primary and secondary OSSE targets.
During the observations of the galactic center region, OSSE will obtain data
at scan angles separated by one degree. These data will be used, along with
data acquired during viewing period 5 and the data to be acquired during
viewing periods 14, 16, and 17, to study the distribution of diffuse 0.51 and
1.81 MeV emission and to search for the variable line emission reported from
1E1740.7-2942 and the HEAO-A4 source near galactic position long = 3.1,
lat = -13.9. Coordinated observations will be obtained with GRANAT/SIGMA and
the sources 1E1740.9-2942, GX 1+4, and GRS 1758-258 will be given additional
observation time.
Since the Sun will be accessible to all GRO instruments during viewing
period 11, this viewing period has been designated part of the MAX '91
solar flare campaign during which a variety of observatories around the world
will be carrying out coordinated observations of the Sun. The Sun will be in
the OSSE field-of-view during some of the 3C 273 observations. OSSE will also
respond to BATSE solar flare triggers by re-pointing detectors to observe the
Sun for a period of about 1000 seconds.
Article: 17342
From: [email protected] (Daniel Fischer)
Newsgroups: sci.astro,sci.physics,sci.space
Subject: The Gamma Ray Burster Mystery - Galactic Neutron Stars After all?
Date: 7 Oct 91 10:52:12 GMT
Organization: Max-Planck-Institut fuer Radioastronomie, Bonn
According to NASA's news releases and several space media (AW&ST, SPACE NEWS,
SKYLINE) the BATSE instrument on the Compton Observatory (formerly known as
the GRO) has made an earth-shaking discovery: the sources of the famous Gamma
Ray Bursts are distributed isotropically in the sky; there's no preference
for either the galactic plane or the galactic center region. This is being
interpreted as evidence that galactic neutron stars are *not* involved, and
that the sources but be either very near (tens of lightyears) or very far away,
at the edge of the observable universe. Is that convincing? Prof. W. Kundt of
Bonn's Institute for Astrophysics not agree at all:
] {The NASA news release} is an overkill: an isotropic distribution of GRB's
] does not exclude (nearby) neutron stars!! (Refer to A.Harding, Physics
] Reports 1991. {Someone knows the complete reference?}) Old neutron stars have
] a scale height of SEVERAL KPC, therefore they're distributed almost
] ISOTROPICALLY up to several kpc. If they swallow their food slowly, thru an
] accretion disk (.l.e.10^7a), anisotropy must not necessarily be expected;
] even a peak overhead, at large z, is possible. The typical distance of the
] bursts (calculated via their Eddington luminosities) is 300pc; that
] contains 1/1000 of all (.g.e.10^10) galactic neutron stars -> .G.E. 10^7
] SOURCES.
Sounds logical, doesn't it? But why is it then that - as far as we hear here -
most GRB theorists are willing to give up the neutron star hypothesis? The
Skyline news hotline of Sky&Telescope, e.g., says that the the "theorists are
falling all over themselves" in frantic attempts to come up with a new class
of candidate objects.
So, I'm completely undecided on whether the discovery is something fundamental
or just another bad case of NASA PR hype. Weren't the arguments for neutron
stars as the source (working by whatever mechanism) rather strong (pulsed
signal in bursts in .g.e.2 cases; strong fields)? Can statistics working on
just 120 events really destroy all that evidence?
+- [email protected] --- Daniel Fischer --- [email protected] -+
| Max-Planck-Institut f. Radioastronomie, Auf dem Huegel 69, W-5300 Bonn 1,FRG |
+----- Enjoy the Universe - it's the only one you're likely to experience -----+
P.S.: NASA also spoke of other GRO mysteries, but here the info is even more
sketchy. Did they really say that the whole galactic disk is emmitting 511
keV line radiation? Does someone have info going beyond what was posted here
so far on the 23 Sept. GRO renaming news conference?
Article: 17348
From: [email protected] (peter edward freeman)
Newsgroups: sci.astro
Subject: Re: The Gamma Ray Burster Mystery - Galactic Neutron Stars After all?
Date: 7 Oct 91 16:02:32 GMT
Sender: [email protected] (NewsMistress)
Organization: University of Chicago
Daniel Fischer --- [email protected]:
> Sounds logical, doesn't it? But why is it then that - as far as we hear here -
> most GRB theorists are willing to give up the neutron star hypothesis? The
> Skyline news hotline of Sky&Telescope, e.g., says that the the "theorists are
> falling all over themselves" in frantic attempts to come up with a new class
> of candidate objects.
> So, I'm completely undecided on whether the discovery is something fundamental
> or just another bad case of NASA PR hype. Weren't the arguments for neutron
> stars as the source (working by whatever mechanism) rather strong (pulsed
> signal in bursts in .g.e.2 cases; strong fields)? Can statistics working on
> just 120 events really destroy all that evidence?
Don Lamb here at the U. of Chicago was, I believe, involved in some calcula-
tions that said, roughly, to get an isotropic distribution, you can only
look out to one fifth to one tenth of the scale height. But if the scale
height of galactic neutron stars is, say, three kpc, and the distances implied
by the Eddington luminosity are correct (say 300 pc), then there appears to
be no problem. Whether this "no problem" result survives further refinements
in the calculation, we will see.
As far as 117 bursts destroying the hypothesis, well, they can't. I am not
perturbed by the idea that the neutron star hypothesis may be wrong; if the
observed cyclotron lines (which imply strong fields which only a neutron
star can provide) are indeed artifacts, then there is no evidence against a
cosmological origin for GRBs. What I am perturbed about is the fact that
supposedly good scientists at NASA are concluding that the NS hypothesis is
wrong, when the data they presented at the Goddard conference do not necessarily
allow this conlusion (actually, better stated, the data do not rule out the
NS hypothesis). And I am perturbed that this premature finding is becoming
dogma by being disseminated throughout all the popular science journals.
Overheard at a cocktail party: "Oh, you work with those burst things. What was
that? Neutron stars? But everyone knows that that theory has gone the way
of the dodo. I read it in the New York Times..."
O.K., so this actually hasn't happened yet :-)
Peter Freeman
[email protected]
Article: 17350
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Re: The Gamma Ray Burster Mystery - Galactic Neutron Stars After all?
Date: 7 Oct 91 15:35:47 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
There has been some confusion on the net as to why the
BATSE results are so interesting. There are actually two
results, either one of which can be explained using the conventional
picture of bursts from neutron stars, but which in conjunction are
very difficult to deal with.
First, the distrubution of bursts in the sky is isotropic, i.e. there is
not preferred direction.
Second, the distribution of bursts in brightness is not consistent with
a uniform density of bursts as a function of radius, i.e., there are not
enough faint (and therefore distant) bursts. This is often expressed
in terms of the V/Vmax test. What one does is consider a given burst and
consider how much fainter the burst have been and still have been detected.
Suppose the burst could have been a factor of 4 fainter, then we could
have detected it even if it had been about 2 times further away. In general
we should expect that if bursts are uniformly distributed in space, the
ratio of the volume of space enclosed by the radius at which the burst
actually took place, to the volume of space enclosed by the maximum radius
it could have been detected at is 0.5. This is independent of any
distribution of intrinsic brightnesses of the bursts. Also, to measure
this ratio, we don't actually need to know the intrinsic brightness,
the apparent brightness of the burst is enough. For the BATSE burst
this V/Vmax ratio is about 0.35 +- 0.04. Bursts are clustered preferentially
near to us.
Getting back to what the results mean in terms of where the bursts can be:
The second result implies that we are seeing some kind of edge in the
distribution, the first that the edge is spherical with the earth near
the center (near being defined in terms of the radius to the edge).
Together these constraints seem to rule out distributions similar to any
observed stellar distribution. Some guesses as to where you can put
the bursters are:
in the Oort cloud (the cometary halo around the Sun).
in a galactic halo population where the core radius of the halo
is at least 50-100 Kiloparsecs (i.e., 5-10 times the radius of
the sun from the center of the galaxy. Putting them any nearer
in the Galaxy would mean that we should see some preference for
the bursts towards the center of the galaxy. This is much more
diffuse than any observed stellar population.
at cosmological distances, i.e., gigaparsecs away.
Each of these alternatives has significant problems with other observations
that have been made of bursts. There are lots of theories being bandied
about right now, invoking beaming or collisions of neutron stars, or
whatever anyone can dream up, but right now there is no theory that
seems to explain all the data. Of course one possibility is that there
are several different progenitors for bursts, but all this does is
relegate the problem to some of the subclasses. It is a lot of fun
watching people try to explain all of this.
Tom McGlynn
Compton Observatory Science Support Center
[email protected]
grossc::mcglynn
Although I do work with the Compton Observatory, I am not a member of
the BATSE team nor a specialist in gamma ray bursts, and my remarks are
not in any way official, just speculation from an interested bystander.
|
| 636.29 | GRO Science Report - October 10 | MTWAIN::KLAES | All the Universe, or nothing! | Fri Oct 11 1991 13:04 | 113 |
| Article: 17413
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory (GRO) Science Report:
Date: 10 Oct 91 19:00:37 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
GRO Science Report #34
Thursday, October 10, 1991
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the CGRO SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
MAX '91 Campaign
----------------
The FLARES22/MAX91 solar observing campaign continues through October 17.
Recent solar activity reports show low to moderate activity, with a few
M-class x-ray bursts and many C-class bursts. A message from Sac Peak
yesterday (October 9) reported intense coronal emissions over the East
solar limb at that time.
Spacecraft Status:
------------------
Normal operations continue.
On October 9 at 06:01 UT (2:01 a.m. EDT), the Compton GRO transponders
experienced another high RF signal over Indonesia that caused receiver
A to go into a lockout condition very similar to the situation that
occurred a week ago on October 2. Again, Receiver B saw the
interfering signal but did not go into the lockout condition.
Previously developed lockout recovery procedures were used
successfully, and recovery was accomplished before the end of the TDRS
contact at 7:34 UT. Since receiver B was in the normal configuration
for real-time operations, there was NO LOSS of COMMUNICATION with the
satellite and NO LOSS of SCIENCE DATA.
The tape recorder bit error rate continues to decline gradually, as it has
for the past few weeks. This is an encouraging indication.
Other News
----------
The Huntsville Gamma-Ray Burst Workshop will be held on October 16-18.
This meeting should be of great interest, in light of the major
announcements made by the BATSE team at the Second GRO Science
Workshop last week. For more information on where/when read item #1
on GRONEWS. (set host to GROSSC, then log in as "GRONEWS").
INSTRUMENT REPORTS:
EGRET
-----
The EGRET operations continue to run smoothly. The instrument performance
remains essentially unchanged. As noted last week, in a part of the current
period the instrument will be operated with the TASC not in coincidence in
order to enhance the low energy sensitivity.
Work on the in-flight calibration and analysis paper continues. Several
analyses of flight data are progressing simultaneously, including studies on
pulsars, the Cygnus region, quasars, the Large Magellanic Cloud, bursts, and
the galactic center region.
BATSE
-----
As of October 9th, BATSE has detected 142 cosmic gamma-ray bursts
out of a total of 778 on-board triggers in 171 days of operation.
There have been 214 triggers due to solar flares with emission above
60 keV.
The BATSE team is in a state of high activity in preparation for the
upcoming Gamma Ray Burst Workshop in Huntsville, October 16-18. 115
participants are registered to attend the workshop, including 39 from
outside the U.S. Foreign participants will represent the science
communities of Canada, Czechoslovakia, Denmark, England, France,
Germany, Japan, India, Italy, the Netherlands, Poland and the
U.S.S.R. The Gamma Ray Burst Workshop is being sponsored by the
Alabama Space Grant Consortium, NASA/MSFC, UAH, and U.S.R.A.
COMPTEL
-------
Routine operations continue with COMPTEL. Almost all members of the COMPTEL
team are meeting at ESTEC in Holland this week to assess instrument
performance to date, to review all routine data analysis procedures, and
to continue work on initial scientific results from COMPTEL.
For the current period of 10/3 through 10/9, COMPTEL has received no solar
triggers from BATSE.
OSSE
----
OSSE continues to operate well. For the current observing period through 10/9,
OSSE has received no solar triggers from BATSE.
As part of the continuing checks of the instrument's performance, OSSE has been
configured to examine the high time resolution stability of its high voltage
PMT supplies during those periods of each orbit when the OSSE primary and
secondary targets are occulted by the Earth. The time resolution for this
study is approximately 2 seconds.
The OSSE team is submitting several papers for the January AAS meeting in
Atlanta, GA. J. Kurfess will also be presenting an invited paper on initial
OSSE results at this meeting.
Posted by:
Tom McGlynn
Compton Observatory
Science Support Center
Goddard Space Flight Center
Internet: [email protected]
SPAN: GROSSC(15765)::MCGLYNN
|
| 636.30 | Compton Observatory Science report #35 | PRAGMA::GRIFFIN | Dave Griffin | Tue Oct 22 1991 19:53 | 106 |
| From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Date: 17 Oct 91 18:42:41 GMT
Organization: Goddard Space Flight Center
GRO Science Report #35
Thursday, October 17, 1991
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the CGRO SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Spacecraft Status:
------------------
Normal operations continue. A maneuver from the 3C273 attitude of period
11 to the Cen A attitude of period 12 was performed today, from 1357-1433Z.
No communications lockouts have occurred in the past week.
TRW presented the report on their study of the CGRO propulsion system
at GSFC on October 16. They have done a series of numerical simulations
of the system's behavior as valves are opened, and have built and run a
hardware test system to check their numerical assumptions. Decisions
will be made soon on the procedures for use of the propulsion system for
reboost of CGRO. It still appears most likely that reboost will be done
when the CGRO orbital altitude reaches about 380 km, in the Spring of 1993.
Conference at U. Md.
--------------------
On Monday through Wednesday of this week there was a conference at the
University of Maryland, "Testing the AGN Paradigm". The importance of
CGRO observations of 3C 279, 3C273 and other AGNs became very clear
during the course of this meeting.
MAX '91 Campaign
----------------
The FLARES22/MAX91 solar observing campaign continues through today,
October 17. Recent solar activity reports show activity varying from low
to high. The days of high activity have been 10/13 and 10/14, with 10/12
and 10/15 rated moderate. No X-class flares have been reported, but
several M-class flares did occur. For further information on the MAX91
campaign contact Alan Kiplinger at SELVAX::AKIPLINGER or
[email protected]
INSTRUMENT REPORTS:
EGRET
-----
EGRET operations continue to be routine. A total of four full days have
been completed in the TASC-out-of-coincidence, low energy mode during the
most recent period of 10/3-10/17, observing 3C 279 and 3C 273. EGRET is
also continuing weekly charged particle runs for calibration purposes. In
this mode, the anticoincidence of the charged particle shields is disabled
and the TASC can be calibrated using cosmic rays, especially to assure that
the phototube gains are set for uniform response across the detector.
Work on the in-flight calibration and analysis papers continues.
BATSE
-----
The Huntsville Gamma Ray Burst Workshop began yesterday, October 16, and
continues through Friday. The workshop program is available on the BATSE
News Service bulletin board (log in as BNEWS on SPAN node BATSE). The
Huntsville Gamma Ray Burst Workshop is being sponsored by the Alabama
Space Grant Consortium, NASA/MSFC, UAH, and USRA.
BATSE observations of the hard x-ray source GX 339-4 show a dramatic
decrease in its intensity. In the two weeks beginning September 21st
the source's flux decreased from 1/3 Crab to below BATSE's one day
occultation sensitivity level.
COMPTEL
-------
Routine operations continue with COMPTEL. In the course of the last week of the
FLARES22/MAX91 compaign COMPTEL received two solar flare triggers from the
BATSE experiment. Analysis of the COMPTEL "quick-look" data for evidence of
medium-energy gamma-ray emission from these events is underway. The COMPTEL
team reported in IAU Circular No. 5369 the time and measured positions of four
cosmic gamma bursts imaged by COMPTEL on April 25, May 3, June 1, and August
14, 1991. The locations of these bursts on the sky have been measured to an
accuracy of one degree. Several members of the COMPTEL team are attending the
BATSE Gamma Ray Burst Workshop in Huntsville this week, where they are
reporting on these results, and those obtained from earlier observations of
solar flares.
OSSE
----
OSSE is operating well. Starting on October 17, OSSE will begin an observation
of the nearby active galaxy Centaurus A as its primary target and the radio
galaxy 3C390.3 as its secondary target. In addition, since the Sun will be
crossing the OSSE scan plane during viewing period 12, OSSE will remain
configured to respond to Solar flare triggers from BATSE by slewing the
detectors to the Sun and observing the Sun for 1000 seconds.
OSSE has responded to 3 BATSE solar triggers in the past week, on 10/11,
10/12 and 10/14.
Several OSSE team members are attending the Gamma Ray Burst conference in
Huntsville, AL this week. Preliminary data will be presented on OSSE gamma ray
burst observations, including events on 1991 June 1 and 1991 Aug 7 which
were in the field-of-view of OSSE detectors.
posted by:
Tom McGlynn
Compton Observatory Science Support Center
[email protected]
grossc(15765)::mcglynn
|
| 636.31 | Update - October 24 | MTWAIN::KLAES | All the Universe, or nothing! | Fri Oct 25 1991 18:25 | 159 |
| Article: 17826
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report: 36
Date: 25 Oct 91 15:04:44 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
GRO Science Report #36
Thursday, October 24, 1991
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the CGRO SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Spacecraft Status:
------------------
Normal operations continue. No maneuver was scheduled for this week.
No communications lockouts have occurred in the past week.
As reported below by BATSE, the unusual bit errors on tape Recorder A have
rather abruptly disappeared. The reason is not known. This is good
news, and we hope it continues this way.
Washington Area Astronomers Meeting:
-----------------------------------
There was a meeting of local astronomers at the U.S. Naval Observatory
today, at which the afternoon session was devoted to presentations by
the CGRO Project Scientist (Neil Gehrels) and representatives of the
four Compton Observatory Instrument Teams. Some highlights or new
results were:
Robert Hartman presented for EGRET. He said that current estimates of
EGRET gas lifetime are about 4 years. For the Crab light curve, the
intensity outside of the two pulses can essentially all be attributed to
galactic diffuse background emission. The light curves of the Vela and the
Crab in this energy range (~100 MeV) are remarkably similar, although for
Vela both pulses are relatively sharp, while for the Crab the second pulse is
quite broad. The Vela light curve changes significantly as a function of
energy, and for energies above about 500 MeV the "secondary" pulse is the
stronger of the two. A photon spectrum of 3C279 was shown; the spectrum is
straight, with a power law index of 2.0 from 60 MeV to 10 GeV. The last
point at 10 GeV is a bit below the line, but not significantly (1.4 sigma).
A plot of nu-fnu shows that the energy per decade in frequency measured in
gamma rays by EGRET is about 5 times greater than ever seen in any other
frequency range for this source, although it must be noted that these are
not contemporaneous measurements and the source is known to be highly
variable at all frequencies. There may be overlapping X-ray or visible
data, but they are not available yet. The total energy output from 3C279
during the EGRET observation would be 10**48 ergs/sec if it were not beamed,
but the EGRET team believes beaming is most likely. 3C279 was still
visible in the later data from this October, but no details on brightness
were given.
James Ryan presented for COMPTEL. He showed a COMPTEL image of the Crab-
Geminga region. The Crab is very strong, and Geminga may or may not be
marginally visible at this energy range of 1-30MeV. The Crab pulsar also
shows a broad second pulse at COMPTEL energies. The averaged light curve is
time variable at these energies; an observation 2 weeks later showed a much
diminished intensity for the first peak in the light curve relative to
the second.
James Kurfess spoke for OSSE. He showed the count spectrum of the gamma-ray
burst of 1 June 91. The spectrum is smooth, with no obvious features from
80 keV to 2.2 MeV. He compared the OSSE observations of the 511 keV source
near the galactic center and at +/-25 degrees galactic longitude with
calculations for various non-point source distribution models normalized by
the SMM observations of a diffuse source. None agreed extremely well, but
some are close. Observations of 3C273 show definite variability relative
to balloon and spacecraft measurements of 1980 and 1987. The OSSE
intensity measurements are the lowest of the three.
Bonnard Teegarden spoke for BATSE. For the shortest Batse burst, which lasted
only 7 millisec, there is significant time structure on a time scale of 128
microseconds. The distribution of bursts on the sky appears quite uniform, with
no concentration to the galactic plane. For the 37 weakest bursts there is
also no galactic plane effect, although the audience pointed out that 23 of
the 37 bursts were in the northern galactic hemisphere. The distribution of
bursts as a function of V/Vmax is about flat from 1.0 down to 0.3, then rises
for the last 3 points to about 4 times the high-end value for the lowest bin.
This is unlike what would be seen from incomplete sampling of weak bursts,
since here we see an excess of very strong bursts, while incompleteness
produces a deficit of very weak bursts. Expressed as log n(>S) vs log S,
the slope is about -1 from bright bursts down to medium faint, then turns
over to about -0.8 for the faintest bursts (although this change in slope may
be an instrumental effect). The BATSE team never quite sees a slope of -1.5
as a uniform spatial distribution would produce, even for the brightest
bursts. Dr. Teegarden listed the commonly proposed distance scales and
energies for gamma-ray bursts:
Oort Cloud 10**22 ergs/burst 10**4 AU small black holes?
Galactic Halo 10**41 ergs 30 kpc neutron stars
Universe 10**50 ergs 1000 Mpc colliding objects?
INSTRUMENT REPORTS:
EGRET
-----
EGRET operations continue to run smoothly. Scientific analysis of the
data continues.
BATSE
-----
As of October 23th, BATSE has detected 145 cosmic gamma-ray bursts
out of a total of 811 on-board triggers in 185 days of operation.
There have been 232 triggers due to solar flares with emission above 60 keV.
BATSE continues to perform exceptionally well. False triggers have
greatly decreased lately, due to a decrease in solar activity. The
problem with bit errors from the on-board tape recorder has, somewhat
mysteriously, vanished. Currently telemetry errors average about one
bit per day.
The Huntsville Gamma Ray Burst Workshop was held last week on Wednesday
through Friday. As might have been expected, no consensus on the origin
of gamma-ray bursts was reached. The two main camps are the proponents of
sources at cosmological distances, and those who favor neutron stars in
the vicinity of our galaxy. Some ways of expressing the BATSE observations
are: 1. The dipole moment is limited by the measurement of <cos theta>
= -0.005 +/-0.05, where theta is the angle between the source and the
galactic center. 2. <sin**2 B> =0.315+/-0.024, where B is the galactic
latitude of the source. A uniform distribution yields 0.333. Some other
numbers were given above, in connection with today's Washington meeting.
COMPTEL
-------
Routine operations continue with COMPTEL. The Sun remains within the field of
view of COMPTEL (at about 30 degrees off-axis) for the balance of the current
GRO observing period. The solar observing mode of COMPTEL is presently enabled;
upon receipt of a BATSE trigger indicating a solar flare, COMPTEL is
automatically reconfigured into a solar observing mode for about one orbit of
the spacecraft. Though solar activity has been moderate recently, one solar
flare trigger was received by COMPTEL during the past week. Analysis of the
"quick-look" data obtained for this event is underway. A very preliminary
inspection of the energy spectrum of the quasar 3C 273 obtained by COMPTEL
shows agreement at hard x-ray and high gamma-ray energies with previous
measurements of this object. A more quantitative analysis of these data is in
progress.
OSSE
----
OSSE continues to operate well. With the Sun still on the OSSE scan plane,
the OSSE detectors will move to the Sun on receipt of a Solar Flare trigger
from BATSE and observe the Sun for 1000 seconds. However, the OSSE solar flare
response has been modified to terminate any solar observation at the start of
orbital night and resume its normal observations of the primary and secondary
OSSE targets. Between 10/15 and 10/21, OSSE has responded to one BATSE Solar
Flare trigger, which occurred on 10/21.
The OSSE Team will hold a team meeting from 19-21 November at NRL.
posted by:
Tom McGlynn
Compton Observatory
Science Support Center
[email protected]
grossc(15765)::mcglynn
|
| 636.32 | Compton GRO Monthly Status Report - 10/30/91 | PRAGMA::GRIFFIN | Dave Griffin | Wed Oct 30 1991 13:22 | 50 |
| ARTHUR HOLLY COMPTON GAMMA RAY OBSERVATORY
MONTHLY STATUS REPORT
October 30, 1991
NASA's Goddard Space Flight Center-managed Compton Gamma Ray
Observatory (Compton) spacecraft and its instruments are performing
well.
Compton is in a normal pointing mode with solar arrays pointed
toward the Sun. The observatory is oriented with the +Z axis
pointed at the galaxy Centaurus A. As of October 23, Compton was
in an orbit with an apogee of 274 miles (441.1 kilometers), and a
perigee of 267.2 miles (430.1 kilometers), period of 93.3 minutes,
and inclination of 28.5 degrees.
The Goddard flight operations team reports that the observatory
is functioning well. The bit errors in the data played back from
onboard Tape Recorder A have declined to the point that they
presently are not significant. The errors that are being observed
have decreased almost to the level expected to be incurred by
normal transmission. Science continues to be performed without
interruption using both the A tape recorder and the redundant B
tape recorder.
Goddard's Energetic Gamma Ray Experiment Telescope (EGRET), is
performing normal operations for the science mission. EGRET
operations continue to run smoothly, according to project
officials. The Burst And Transient Source Experiment (BATSE),
continues to perform exceptionally well according to scientists at
the Marshall Space Flight Center, Huntsville, AL. As of October
23, BATSE had detected 145 cosmic gamma-ray bursts. The source of
these bursts remains a mystery.
The Imaging Compton Telescope (COMPTEL) continues to operate
normally. COMPTEL remains configured to respond to solar flare
triggers from BATSE and there were two such triggers during the
observation period, according to scientists at the Max-Planck
Institute, Germany.
The Oriented Scintillation Spectrometer Experiment (OSSE),
managed by the Naval Research Laboratory, Washington, DC, is
performing normal operations for the science mission. The OSSE
instrument continues to operate well. With the Sun still in the
OSSE scan plane, OSSE remains configured to respond to solar flare
triggers from BATSE by moving the detectors to the Sun and
observing it for 1,000 seconds. The OSSE solar flare response has
been modified to terminate any solar observation at the start of
orbital night and resume its normal observations of the primary and
secondary OSSE targets.
The next Compton maneuver will be to the galactic plane.
Upcoming targets include the galactic plane and the active star-
formation region Eta Carina.
The Compton Observatory is managed and operated by Goddard for
NASA's Office of Space Science and Applications.
-GSFC-
|
| 636.33 | Gamma ray info update | MTWAIN::KLAES | All the Universe, or nothing! | Fri Nov 15 1991 11:04 | 83 |
| Article: 18237
From: [email protected] (Christopher Neufeld)
Newsgroups: sci.astro
Subject: Some notes from a gamma ray burster seminar
Date: 11 Nov 91 06:44:36 GMT
Sender: [email protected] (News Administrator)
Organization: University of Toronto Physics/Astronomy/CITA
Well, last Thursday I took some time out from marking midterms to
attend the weekly colloquium here. Dr. G.J. Fishman from the NASA
Marshall Spaceflight Centre in Alabama, a principal investigator and, I
gather, principal instigator, of the BATSE experiment spoke in some
detail on the results to date. I took notes throughout. A lot of the
information was stuff which I hadn't seen before, so I thought I might
pass it on to the Net.
This is going to look a bit like point form, but it's late and I
don't have time to clean this up too much.
The gamma ray bursts last anywhere from 10 millisecond to 500
seconds, with energies between 2 keV and 200 MeV, but mostly in the 100
to 600 keV range. Previous Japanese and USSR experiments have reported
spectral lines at 20-60 keV in some bursts, which would correspond to
cyclotron lines for fields around 1E11 to 1E12 Gauss. A soviet
experiment also reported in about 5% of bursts a 450 keV line which is
speculated to represent red-shifted electron-positron annihilation
radiation. This last result is unconfirmed. There is a notable
deficiency of X-rays (<2%), and there is often rapid spectral variation
within a burst.
A U.S. spacecraft, Vela, noticed these bursts at a rate of about
10/yr. Later generation Soviet craft reported about 80/yr. BATSE aboard
the GRO is seeing 300/yr and by factoring in duty cycle considerations
(the experiment doesn't run at high radiation times, I presume this
means the South Atlantic anomoly, and I imagine Earth still subtends
a considerable portion of the sky since the GRO is in a shuttle-capable
orbit) they extrapolate to about 800 events per year.
BATSE is capable of localization on strong bursts to within several
degrees. It consists of 8 detectors at the corners of the roughly
box-shaped spacecraft. Ulysses has a gamma ray detector which provides
basline data allowing the bursts to be localized to within an annulus,
and when Mars Observer goes up it will provide the third locator station
necessary to get angular position unambiguously. I presume these are for
the weaker bursts which BATSE cannot localize to within the several degrees.
The GRO's fuel supply will last about 15 years, but it is capable of
on-orbit refueling.
The trigger on the experiment is a coincidence of all the following:
60-300 keV detected 64, 256, or 1024 millisecond (I don't know what this
means) 5.5 sigmas above background on two or more detectors
Dr Fishman went on to show some bursts, which are resolved on 0.2
millisecond time scales with a two second pre-trigger (continually
refreshed through a circular buffer). Two in particular looked very
interesting, consisting of a sharp, short startup and quick decay, then
a delay of 55 seconds in one case and 110 seconds in another, followed
by a long, sustained, highly energetic burst which easily exceeded the
power of the burst which triggered the data acquisition.
Accumulated data for over a hundred strong bursts was shown on a
latitude/longitude coordinate system, and analyzed to show that the
dipole and quadrupole moments are consistent within errors to an
isotropic distribution (zero for the dipole, one third for the quadrupole).
A graph which shows number of events as a function of estimated
distance was shown to have an elbow indicating that the bursts were
preferentially close to us on whatever distance scale they appear. I'm
sure an astronomer could explain this paragraph better than I can.
The three regimes being looked at for explanation of the results
are: Solar system associated events implying new objects. Large
galactic halo events, even though there is no other strong evidence
for the presence of such an extended galactic halo (on a distance
scale of ten or more times the size of the visible galaxy). Cosmological
distance events with energy outputs in the range of 1E53 ergs.
--
Christopher Neufeld....Just a graduate student | The best defense
[email protected] Ad astra | against logic is
cneufeld@{pnet91,pro-cco}.cts.com | ignorance.
"Don't edit reality for the sake of simplicity" |
|
| 636.34 | Updates - November 7 and 14 | MTWAIN::KLAES | All the Universe, or nothing! | Mon Nov 18 1991 18:35 | 248 |
| Article: 18266
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #38
Date: 12 Nov 91 17:48:42 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton GRO Science Report #38
Thursday, November 7, 1991
Chris Shrader, Compton GRO-Science Support Center
Questions or comments can be sent to the GRO SSC. Phone 301/286-8434,
e-mail SPAN GROSSC::SHRADER, Internet [email protected].
---------------------------------------------------------------------
CURRENT OBSERVATORY STATUS:
---------------------------
Compton GRO is in normal pointing mode (NPM) with solar arrays
pointed toward the sun. The observatory was maneuvered to point the
Z-axis towards (lII,bII) = (337, -84), at 311:14:34:50 UT. This
orientation will allow OSSE to view the galactic x-ray binary GX339-4.
All spacecraft subsystems are operating nominally. The transponder
lockout condition has not re-occurred since October 9.
Flight Dynamics has determined that there would be a problem with moon
interference in the star trackers if the maneuver from ETA CAR to NGC1275
were to occur on November 27 as scheduled. This may result in the maneuver
being rescheduled by one day (in which case the moon is clear of the
star tracker fov).
UPCOMING MANEUVERS:
PERIOD MANEUVER DATE +Z AXIS (COMPTEL AND EGRET) TARGET
14 November 14 ETA CAR
15 November 27* NGC 1275
16 December 12 SCO X-1
17 December 27 SN 1987A
* see above.
Instrument Reports:
-------------------
BATSE:
-----
As of November 5th, BATSE has detected 154 cosmic gamma-ray bursts
out of a total of 898 on-board triggers in 198 days of operation.
There have been 279 triggers due to solar flares with emission above
60 keV.
During Viewing period 1-13.2, BATSE folded on board pulsar data will
be collected for the Crab Pulsar, Cen X-3, PSR 1509-58, and Her X-1.
COMPTEL:
--------
Routine operations continue with COMPTEL. The instrument is functioning
well, and the routine processing of incoming flight data is proceeding
on schedule.
EGRET:
------
EGRET operations are continuing in a routine manner. Performance
monitoring continues.
The article "Detection of High Energy Gamma Rays from Quasar 3C 279
by the EGRET Telescope on the Gamma Ray Observatory" has been accepted
for publication in the Astrophysical Journal Letters. The referee described
the paper as representing "one of the most important discoveries in high
energy astrophysics of the last decade." The Quasar, seen over the entire
range from below 100 MeV to 10 GeV, is the most luminous and most distant
source of gamma rays seen to date. If the radiation is isotropic, during
the two weeks that the source was viewed it was emitting high energy
gamma rays at the rate of 10**48 ergs/sec. Even if the source is beamed,
the observed flux represents an astounding energy release, especially
considering the mechanisms that are needed to produce high energy gamma
rays.
Other News:
-----------
The Compton GRO Science Support Center staff is currently collecting and
reviewing manuscripts for the Compton Science Workshop Proceedings. It is
anticipated that copies of the proceedings will be available for
distributions by the late January/early February 1992 time frame. The
SSC, in support of NASA HQ, has also begun preparation for the phase 2
proposal review, tentatively set for February 24-26, as well as the review
for second year Compton Fellowship Program, January 30,31.
Several software tools of potential use to phase 2 proposers have been
added to the GRONEWS facility maintained by the SSC. These allow users
to calculate target viewing windows and (for EGRET) effective collecting
area for off-axis positions.
A version of the time line using galactic coordinates is available on
GRONEWS.
Posted by:
Tom McGlynn
Compton Observatory
Science Support Center
Goddard Space Flight Center
Internet: [email protected]
SPAN: GROSSC(15765)::MCGLYNN
Article: 18323
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #39.
Date: 14 Nov 91 23:28:08 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
GRO Science Report #39
Thursday, November 14, 1991
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the CGRO SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Spacecraft Status:
------------------
Normal operations continue. A maneuver to the attitude of period 14
(z-axis at Eta Carinae, OSSE other target is the Galactic Center) took
place from 1547Z to 1615Z today. No communications lockouts have occurred
recently. The tape recorder bit error rate shows a very slight rise over
the past two weeks, but is still far below the average of the past few
months.
INSTRUMENT REPORTS:
EGRET
-----
EGRET operations continue in a routine manner. Performance monitoring
continues. The EGRET spark chamber gas will be changed on December 2 and 3,
1991. Based on this first refill occurring nearer to eight months than six,
the lifetime now is estimated to be in the range of 3.6 to 4 years, if there
are no problems. In addition, as mentioned several times before, the last
approximately 15% of the gas could be saved for special event studies and the
observation of time varying sources thereby extending the time over which
data is collected.
A paper on the May 3, 1991 burst has been submitted. This is the first burst
event that has been seen by imaging detectors, COMPTEL and EGRET. In
addition, EGRET obtained three spectra during the event covering the range
from 1 to 200 MeV. EGRET scientists are also in the process of studying
data from solar flares. Work is also continuing on other sources. The
calibration study including the in-flight portion is nearly finished and the
associated paper is nearing completion.
BATSE
-----
As of November 12th, BATSE has detected 162 cosmic gamma-ray bursts
out of a total of 942 on-board triggers in 205 days of operation.
There have been 290 triggers due to solar flares with emission above
60 keV.
During Viewing period 14, BATSE folded on board pulsar data will
be collected for the Crab Pulsar, SMC X-1, the Vela Pulsar, and Her X-1.
Over the last weekend power was cut-off in the communications building
at MSFC for maintainance. This caused a two day loss of the X.25 link.
BATSE mission operations are now fully caught-up.
COMPTEL
-------
Routine operations continue with COMPTEL; the instrument is performing well.
The solar observing mode of COMPTEL has been disabled until the Sun is once
again within the field of view of the instrument. COMPTEL also experienced a
"soft upset" in the memory of its on-board computer on 5 November, 2 days
before a similar event reported by OSSE. The error was automatically identified
and corrected with no loss of data, or degradation in instrument performance.
Similar errors were apparently observed in other satellites within a day or so
of the COMPTEL occurence. Analysis of these anomalies is continuing; the
possibility that they may be due to unusual solar particle events is being
investigated.
OSSE
----
OSSE continues to operate well. For viewing period 14, the OSSE detector
scan plane is along the galactic plane and the primary OSSE target is the
Galactic Center region, which OSSE will observe at one degree spacings along
the plane within 6 degrees of the Center. The secondary OSSE target for this
viewing period is the Eta Carina region.
Between 2 November and 11 November, OSSE has slewed to the Sun on 7 occasions
in response to BATSE solar flare triggers. These slews occurred at the
following Truncated Julian Day numbers: 8568.12, 8568.71, 8569.87, 8570.06,
8570.84, 8571.17, and 8571.69.
Compton Observatory Timeline in Galactic Coordinates:
In response to some requests, the following is the current observing
timeline for Phase 1, with coordinates given in galactic latitude and
longitude. There are no significant differences from the previous celestial-
coordinates timelines, except that the maneuver planned for November 27
has now been moved back to its original date of November 28.
COMPTON OBSERVATORY OBSERVING PLAN AS OF 11/14/91
Coordinates listed below are Galactic [ LII, BII ]
Run Start Date Stop Date GRO Z Axis GRO X Axis OSSE Primary Target OSSE Secondary Target
---- ----------- ----------- ------------- ------------- --------------------------- ---------------------------
1 16-MAY-1991 30-MAY-1991 190.93 -4.74 100.06 -10.30 CRAB PULSAR 184.50 -5.87 PSR 1957+20 59.17 -4.65
2 30-MAY-1991 8-JUN-1991 73.28 2.56 162.60 -14.79 CYG X-1 71.34 3.07 NGC 1275 150.58 -13.26
2.1 8-JUN-1991 15-JUN-1991 194.86 -7.29 104.63 -1.91 SUN 195.05 -7.39 CYG X-1 71.34 3.07
3 15-JUN-1991 28-JUN-1991 299.78 65.45 211.39 -0.74 SN 1991T 292.61 65.18 QSO 0736+016 216.99 11.38
4 28-JUN-1991 12-JUL-1991 156.19 72.08 161.97 -17.84 NGC 4151 155.08 75.06 3C 111 161.68 -8.82
5 12-JUL-1991 26-JUL-1991 0.00 -4.00 0.00 86.00 G CENTER 0+0 0.00 0.00
6 26-JUL-1991 8-AUG-1991 278.00 -29.32 229.73 49.85 SN 1987A 279.70 -31.94 MRK 421 179.84 65.03
7.1 8-AUG-1991 15-AUG-1991 70.44 -8.30 152.66 42.84 CYG X-3 307.66 40.78 M82 141.42 40.57
7.2 15-AUG-1991 22-AUG-1991 25.00 -14.00 25.00 76.00 G PLANE 25 25.00 0.00
8 22-AUG-1991 5-SEP-1991 262.94 -5.67 328.85 76.33 VELA PULSAR 263.59 -2.74 SN 1991T 292.61 65.18
9.1 5-SEP-1991 12-SEP-1991 338.97 -83.50 338.94 6.50 GX 339-4 338.94 -4.33 NGC 253 97.40 -87.96
9.2 12-SEP-1991 19-SEP-1991 59.67 40.28 205.41 44.29 HER X-1 58.15 37.52 MRK 421 179.84 65.03
10 19-SEP-1991 3-OCT-1991 287.85 -54.30 300.14 35.07 NOVA MUS 295.30 -7.08 3C 279 305.11 57.06
11 3-OCT-1991 17-OCT-1991 294.25 63.67 4.35 -9.56 3C 273 289.96 64.36 G CENTER 0+0 0.00 0.00
12 17-OCT-1991 31-OCT-1991 310.71 22.21 84.25 59.34 CEN A 309.53 19.42 3C 390.3 111.43 27.07
13.1 31-OCT-1991 7-NOV-1991 25.00 -14.00 25.00 76.00 G PLANE 25 25.00 0.00 NGC 5548 31.94 70.49
13.2 7-NOV-1991 14-NOV-1991 338.97 -83.50 338.94 6.50 GX 339-4 338.94 -4.33 ESO 141-55 338.18 -26.71
14 14-NOV-1991 28-NOV-1991 285.04 -0.74 15.04 0.20 ETA CAR 288.04 -0.73 G CENTER 0+0 0.00 0.00
15 28-NOV-1991 12-DEC-1991 147.52 -12.96 58.89 5.95 NGC 1275 150.58 -13.26 CYG X-1 71.34 3.07
16 12-DEC-1991 27-DEC-1991 0.00 20.29 0.00 -69.71 G CENTER 0+0 0.00 0.00
17 27-DEC-1991 10-JAN-1992 283.21 -31.62 9.52 5.97 SN 1987A 279.70 -31.94 G CENTER 0+0 0.00 0.00
18 10-JAN-1992 23-JAN-1992 137.47 40.49 49.35 -2.20 M82 141.42 40.57 PSR 1929+10 47.38 -3.88
19 23-JAN-1992 6-FEB-1992 58.15 -43.00 58.15 47.00 G PLANE 58.1 58.15 0.00 HER X-1 58.15 37.52
20 6-FEB-1992 20-FEB-1992 39.70 1.76 39.70 -88.24 SS 433 39.70 -2.24
21 20-FEB-1992 5-MAR-1992 171.21 -54.88 4.22 -34.42 NGC 1068 172.11 -51.93 G CENTER 0+0 0.00 0.00
22 5-MAR-1992 19-MAR-1992 115.35 44.88 123.69 -44.81 MRK 279 115.05 46.87 M 31 121.18 -21.57
23 19-MAR-1992 2-APR-1992 322.14 3.01 322.14 -87.00 CIR X-1 322.14 0.01
24 2-APR-1992 16-APR-1992 108.77 -41.42 238.48 -35.91 MRK 335 108.77 -41.42 VELA X-1 263.06 3.93
25 16-APR-1992 30-APR-1992 9.53 57.15 118.92 12.10 4U 0115+634 126.16 -0.21
26 30-APR-1992 14-MAY-1992 164.06 7.90 85.92 -55.96 MCG +8-11-11 165.73 10.41 III ZW 2 106.98 -50.63
27 14-MAY-1992 28-MAY-1992 224.00 -40.00 139.44 6.45 3C 390.3 111.43 27.07 SN 1987A 279.70 -31.94
28 28-MAY-1992 11-JUN-1992 108.75 -2.37 198.56 4.42 CAS A 111.74 -2.14 GEMINGA 195.14 4.27
29 11-JUN-1992 25-JUN-1992 252.41 30.65 183.98 -31.81 NGC 2992 249.71 28.78 3C 120 190.37 -27.40
30 25-JUN-1992 9-JUL-1992 335.10 -25.56 255.63 20.92 ESO 141-55 338.18 -26.71 MCG -5-23-16 262.75 17.23
31 9-JUL-1992 23-JUL-1992 225.46 1.95 323.60 76.50 M 87 283.78 74.49
32 23-JUL-1992 6-AUG-1992 13.10 -53.32 267.65 -11.22 PKS 2155-304 17.74 -52.25 SMC X-1 300.46 -43.57
33 6-AUG-1992 20-AUG-1992 196.66 45.66 299.00 11.80 MCG +5-23-16 200.83 46.46 NGC 3783 287.46 22.95
Posted by:
Tom McGlynn
Compton Observatory Science Suppport Center
Goddard Space Flight Center
Internet: [email protected]
Span: GROSSC(15765)::mcglynn
|
| 636.35 | Update - November 21 | MTWAIN::KLAES | All the Universe, or nothing! | Fri Nov 22 1991 13:38 | 81 |
| Article: 18385
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #40
Date: 21 Nov 91 22:04:07 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #40
Thursday, November 21, 1991
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Spacecraft Status:
------------------
Normal operations continue. The bit error rate on Tape Recorder A has
been increasing since the last maneuver, and is now at approximately
the high rate of last summer. This is being watched closely, of course.
INSTRUMENT REPORTS:
EGRET
-----
EGRET operations continue in a routine manner. During the current
observation period, EGRET has been placed in the TASC OUT of coincidence mode
for three of the fourteen observing days in order to obtain more information
on the low energy part of the spectrum from the galactic plane. The gas
refill is still planned for December 2 and 3, 1991 as described last week in
more detail. As noted before, the automatic detection and flag mode for
microsecond bursts is not functionimg properly; it is not possible to
determine the specific reason. A search is being made for the possibility of
microsecond bursts in the study of the events; this procedure is slower, but
probably would have been used anyway. Microsecond bursts will show up as
multiple (many-pair) tracks in triggered spark chamber images.
It was noted last week that a paper on the May 3, 1991 burst was submitted.
The EGRET group is now working with a large group of scientists both within
GRO and from other satellites to develop a study of that event combining the
available data from many sources. Work is also in progress on several other
papers on various sources. The preprint of the EGRET paper on 3C279 for
Ap.J.Lett. by R. Hartman et. al. is now available from Code 662 at GSFC.
BATSE
-----
As of November 19th, BATSE has detected 168 cosmic gamma-ray bursts
out of a total of 982 on-board triggers in 212 days of operation.
There have been 295 triggers due to solar flares with emission above
60 keV.
A paper has been submitted to Nature describing the BATSE observations
of the angular distribution of gamma-ray bursts. A total of 21 papers
on BATSE observations will be presented at the Atlanta AAS meeting in
January.
COMPTEL
-------
Routine operations continue with COMPTEL; the instrument is performing well.
The routine processing of COMPTEL flight data has been completed through the
observations of Observing Period 9. The routine processing of the flight data
for O.P. 10 (Fairall 9) is well underway. The scientific analysis of these data
is continuing. A paper by the collaboration on "The Gamma-Ray Burst of 03 May
1991 Observed by COMPTEL on board GRO" has been accepted for publication and
will appear shortly in the journal Astronomy and Astrophysics.
OSSE
----
OSSE continues to operate well. An OSSE Science Team meeting is being held
at NRL over November 19-21.
Between 11 November and 21 November, OSSE has responded to BATSE solar flare
triggers with slews to the Sun on 3 occasions, at Truncated Julian Day numbers:
8571.17, 8571.69, 8572.89
Posted by:
Tom McGlynn
Compton Observatory Science Support Center
Internet: [email protected]
SPAN: GROSSC(15765)::mcglynn
|
| 636.36 | Compton GRO Monthly Status - November, 1991 | PRAGMA::GRIFFIN | Dave Griffin | Tue Dec 03 1991 13:17 | 63 |
| ARTHUR HOLLY COMPTON GAMMA RAY OBSERVATORY
MONTHLY STATUS REPORT
November 30, 1991
NASA's Goddard Space Flight Center-managed Compton Gamma Ray
Observatory (Compton) spacecraft and its instruments continue to
perform well.
Compton is in normal pointing mode with solar arrays pointed
toward the Sun. The observatory is oriented with the +Z axis
pointed at the active Galaxy NGC 1275. As of November 26,
Compton was in an orbit with an apogee of 271 miles (436.2
kilometers), and a perigee of 263.6 miles (424.3 kilometers),
period of 93.2 minutes, and inclination of 28.5 degrees.
The Goddard flight operations team report the observatory is
functioning well. The number of bit errors in the data played
back from on-board Tape Recorder A has continued to increase
significantly beyond previously observed rates. Instrument teams
reported the error rate increase had begun to affect the
processing of science data. Therefore, the flight operations
team changed onboard recording procedures on November 29, and is
now using Tape Recorder B as the primary recorder for mission
data, supplemented with realtime data. Tape Recorder A will be
used as a backup and its performance will continue to be
monitored. Since the change-over to Tape Recorder B, the error
rate has declined dramatically and is within acceptable levels.
Goddard's Energetic Gamma Ray Experiment Telescope (EGRET), is
performing normal operations for the science mission. EGRET
operations continue to run better than expected, according to
project officials. On December 2, flight controllers will send a
series of commands that will execute the first refill of EGRET's
spark chamber with neon gas. EGRET's spark chamber contains one
atmosphere of neon gas that must be refilled periodically from
on-board storage spheres. The capability exists for five refills
of neon. The gas is being depleted at the rate predicted by
project officials prior to launch.
The Burst And Transient Source Experiment (BATSE), continues
to perform exceptionally well, according to scientists at the
Marshall Space Flight Center, Huntsville, AL. As of November 25,
BATSE had detected 176 cosmic gamma-ray bursts. The source of
these bursts remains a mystery.
The Imaging Compton Telescope (COMPTEL) continues to operate
normally, the scientists at the Max-Planck Institute, Germany
reported.
The Oriented Scintillation Spectrometer Experiment (OSSE),
managed by the Naval Research Laboratory, Washington, DC, is
performing normal operations for the science mission. The OSSE
instrument continues to operate well. With the Sun still in the
OSSE scan plane, OSSE remains configured to respond to solar
flare triggers from BATSE by moving the detectors to the Sun and
observing it for 1,000 seconds. OSSE has responded to ten such
triggers during the past month. The OSSE solar flare response
has been modified to terminate any solar observation at the start
of orbital night and resume its normal observations of the
primary and secondary OSSE targets.
The next Compton maneuver will be to the sixteenth scheduled
phase one target, the binary star SCO X-1, planned for December
12.
The Compton Observatory is managed and operated by Goddard for
NASA's Office of Space Science and Applications.
|
| 636.37 | Update - November 28 | MTWAIN::KLAES | All the Universe, or nothing! | Tue Dec 03 1991 13:33 | 174 |
| Article: 18638
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #41.
Date: 2 Dec 91 14:55:34 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #41
Thursday, November 28, 1991
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
This report is slightly late, due to the Thanksgiving holiday
Spacecraft Status:
------------------
The following note has been received from Robert Wilson, GSFC
Operations Manager:
The rate of bit errors in the data played back from the Compton
Gamma Ray Observatory on-board tape recorder A have continued to
increase significantly since the maneuver on November 14. The
instrument teams have reported that these errors are beginning to
affect the processing of science data. As of 2300Z on November
26, 1991, the Flight Operations Team implemented previously
developed contingency plans to utilize tape recorder B for
mission data, supplemented with realtime data. Tape recorder A
will be used for any missing realtime data and to backup tape
recorder B if needed to fill any gap between TDRS contacts. Tape
recorder A performance will continue to be monitored. (end of msg)
This should not cause any loss of science data for Compton, but of
course Tape Recorder B will get more wear than it would if two tape
recorders were operational. Other than this, operations continues
normally. It is expected that the maneuver of November 28 will
cause a drop in tape recorder temperatures at the new attitude, and
this may help the bit error rate on Tape Recorder A.
As of November 26, Compton GRO was in an orbit with an apogee of 436.3
kilometers, perigee of 424.3 kilometers, period of 93.2 minutes, and
inclination of 28.5 degrees.
On November 28, the Compton Observatory was maneuvered to the
fifteenth scheduled phase I (all-sky survey) target, NGC 1275. The
maneuver of 169 degrees began at 1130Z and was completed at 1221Z.
The final program for the AAS January meeting in Atlanta shows 44
Compton Observatory papers scheduled to be presented, including 4
review papers for the Compton instruments.
The Compton Observatory Science Support Center has developed a DBMS-based
library and bibliography system. This is intended to cover Compton-related
material especially, but our plan is that the entire field of gamma-ray
astronomy will be entered eventually. The library can be accessed by
typing
telnet antwrp.gsfc.nasa.gov
and logging in as gof (password grossc). This service will be made
accessible through GRONEWS soon. A series of menus is presented
on login. On the first menu select 'Query the Libray Database', and
on the second select 'Report Generator Option', or 'Report Generator
Instructions' for information. At the moment the Library Query by Forms
is also operational, but that is somewhat less useful and has poorer
documentation. On the information pages, enter <space bar> for next page,
b = previous page, q = quit.
The Library Query by Report allows the user to generate a compact
report (in file form if desired) of those references which meet
the search criteria. If you create a file you can ftp it back to your
own computer. If the file output is not requested, the report comes to
the screen.
Details on how to do the searches are listed in the 'Report Generator
Instructions'. Please see that if you wish to try this resource. Comments
or complaints or requests for help to me are welcome.
INSTRUMENT REPORTS:
EGRET
-----
EGRET operations remain normal. The gas refill is still planned for
December 2 and 3, 1991. The high tape recorder bit error rate has been
a problem.
The May 3, 1991 burst paper has been accepted by A & A. The study of the
June 11, 1991 solar event is proving to be quite interesting. It and other
results will be reported at the January AAS meeting.
BATSE
-----
As of November 25th, BATSE has detected 176 cosmic gamma-ray bursts
out of a total of 1014 on-board triggers in 218 days of operation.
There have been 297 triggers due to solar flares with emission above
60 keV.
During Viewing period 1-15, BATSE folded on board pulsar data will
be collected for the Crab Pulsar, the Vela Pulsar, Cen X-3,
PSR 1509-58, PSR 0540-69, and Her X-1.
Between Sept. 22 and Oct. 1, flux from GX339-4 dropped below the
current BATSE one-day sensitivity level (~0.1 Crab), with no
significant flux detected as of Nov. 15. BATSE occultation
observations of this black hole candidate had previously shown a
brightening in the 20 to 230 keV energy range. This brightening
period lasted approximately 2 months (June25 - Aug. 22), with the
source remaining at 380 mCrab (20-230 keV) until Sept. 22. The
spectrum appeared to extend to energies of at least 430 keV.
BATSE occultation observations of the x-ray binary 4U1700-37 have
revealed periods of high x-ray flux (20-160 keV). Count rates in
excess of 1.5 Crab between 20-100 keV from 4U1700-37 were measured at
occultation on the following dates/times: Sept 21/.12287 Sept
23/.87218, Oct 23/.95736, Oct 25/.44441, and Nov 12/.81656. These
measurements are evidence of occasional flaring episodes of the source
lasting several hours. This behavior was observed superimposed on the
normal 3.4 day modulation associated with its binary period.
The number of BATSE packets with checksum errors has increased
alarmingly over the last week. The error rate has increased from
150 checksum errors on 18 November to 905 checksum errors on
25 November. This more then 2% of the BATSE data. BATSE operations
are severely hampered by the current high rate of tape recorder
errors. Because of the large size of the error file, emergency
revisions to Operations Software were required to begin processing the
data from November 24th. Numerous problems remain; some are not
completely understood. One burst is missing data needed to measure the
peak rate. At the present error rate, the timely processing of BATSE
science data is seriously compromised.
COMPTEL
-------
Routine operations continue with COMPTEL; the instrument is performing well.
Preprints of the paper "The Gamma-Ray Burst of 03 May 1991 Observed by
COMPTEL on board GRO" may be requested via e-mail to Dr. Chris Winkler at
ESTCS1::CWINKLER or to Dr. Greg Stacy at UNHRCC::STACY, or mail to
Stacy at Univ. of New Hampshire, Science and Eng. Res. Bldg.,
Durham, NH 03824.
The latest solar results will be presented at the AGU meeting in San Fran.
on Tues. Dec 10 a.m. Talking will be Murphy for OSSE, Richard Schwartz for
BATSE and James Ryan for COMPTEL. EGRET will not be represented, since
they had little analysis done at the time the abstracts were due.
Preprints of the GRO workshop papers are available from the authors directly.
All COMPTEL speakers have written up their presentations.
OSSE
----
OSSE continues to operate well. During the current observation period, OSSE
is viewing the active galaxy NGC 1275 as the Z-axis target, and is
obtaining combined observations of the sources Cygnus X-1, Cygnus X-3
and PSR 1951+32 as X-axis targets. For all of these observatios OSSE
will be operated at twice the nominal gain and will cover the energy range
from 40 keV to 5 MeV. For two days during this period, special data
acquisitions of the strong source Cygnus X-1 wll be obtained to improve
knowledge of the instrument detection efficiencies at low energies.
With the Sun inaccessible to direct viewing by OSSE since November 14, OSSE
has not slewed to the Sun in response to BATSE Solar flare triggers since then.
An OSSE team meeting was held during the week of November 18 at NRL. OSSE team
members will be presenting results of early phase 1 observations in eight
contributed papers and one invited paper at the Atlanta AAS meeting.
Posted by:
Tom McGlynn
Compton Observatory Science
Support Center
Internet: [email protected]
SPAN: GROSSC(17565)::mcglynn
|
| 636.38 | Update - December 5 | MTWAIN::KLAES | All the Universe, or nothing! | Mon Dec 09 1991 16:56 | 92 |
| Article: 18760
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #42.
Date: 6 Dec 91 14:45:52 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #42
Thursday, December 5, 1991
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Spacecraft Status:
------------------
The spacecraft continues to operate nominally except that Tape Recorder B
is being used for all telemetry recording. One orbit of science data
was lost during this past week due to insufficient time to dump and
reconfigure Tape Recorder B on one TDRS pass. Tape Recorder A is being
exercised periodically; it has shown a slight drop of the error rate from
the peak just before the maneuver of November 28, but the error rate is
still too large to put it back in service.
INSTRUMENT REPORTS:
EGRET
-----
The EGRET gas venting operation was begun early December 2, 1991 and
completed early December 3, 1991. The refill operation began shortly
thereafter and was completed by noon EST. The instrument was reactivated
by about 1:10 P.M. EST, and the performance of the spark chamber appears to
be as expected. Hence, data is being gathered again. Exact quantitative
analyses will be made over the next week. The Floght Operations Team was
of great assistance during this operation.
BATSE
-----
As of December 3rd, BATSE has detected 184 cosmic gamma-ray bursts
out of a total of 1037 on-board triggers in 226 days of operation.
There have been 304 triggers due to solar flares with emission above
60 keV.
A paper describing the distribution of gamma-ray bursts observed by
BATSE has been accepted for publication in Nature. BATSE observations
of GX 339-4 and 4U 1700-37 were reported in IAU Circulars 5395 and 5394,
respectively, last week.
Discovery magazine included an article on GRO gamma-ray burst
observations among its "50 Top Science Stories of 1991."
COMPTEL
-------
COMPTEL operations continue to run smoothly since the last report. The
integration time for each of the six burst spectra accumulated by the burst
detectors aboard COMPTEL after receipt of a burst trigger has been raised from
0.5 to 1.0 second. Six seconds of data will now be accumulated in the higher
time resolution "burst mode" of data acquisition, which should be sufficient
duration to record emission from the majority of cosmic bursts. The latest
solar results from COMPTEL will be presented next week at the San Francisco
meeting of the American Geophysical Union. Most members of the collaboration
will be attending a COMPTEL team meeting next week at the Max Planck Institute
in Garching, Germany.
OSSE
----
OSSE continues to operate well. The recent increase in lost OSSE data due to
the malfunction of Tape Recorder A on GRO has been alleviated by the change
to operation with Tape Recorder B only. However, because of the continued
occasional use of Tape Recorder A, and possible future increase in the Tape
Recorder B error rate, OSSE recommends implementation of bit-slip data
recovery techniques in ground processing of GRO data as soon as possible.
With the Sun inaccessible to direct viewing by OSSE since November 14, OSSE
has not slewed to the Sun in response to BATSE Solar flare triggers since then.
In respnse to action items from the recent SWT meeting, OSSE viewing program
planners will investigate options for revising the phase 1 viewing program
to accomodate OSSE galactic center observations in period 24 and to accomodate
an earlier observation of NGC 3783 (currently scheduled in period 33).
Posted by:
Tom McGlynn
Compton Observatory Science
Support Center
GSFC
Internet: [email protected]
SPAN: GROSSC(17565)::mcglynn
|
| 636.39 | Update - December 12 | MTWAIN::KLAES | All the Universe, or nothing! | Sat Dec 14 1991 16:41 | 96 |
| Article: 18907
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #43.
Date: 13 Dec 91 15:30:48 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #43
Thursday, December 12, 1991
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Spacecraft Status:
------------------
The spacecraft continues to operate nominally except that Tape Recorder B
is still being used for all telemetry recording. Tape Recorder A is being
exercised periodically; the error rate is down by almost a factor of 2 from
the peak just before the maneuver of November 28, but the error rate is
still too large to put it back in service.
A maneuver was done today to point to the targets of period 16, where the
spacecraft z-axis is close to the galactic center. The maneuver was from
1642Z to 1728Z today, and the maneuver angle was 157 degrees.
INSTRUMENT REPORTS:
EGRET
-----
EGRET operations were normal. The data quality has been much better since
Tape Recorder B has been used for most of the data.
A talk was given by Dave Thompson at the Johns Hopkins physics department
last week and by Carl Fichtel at the Conference on Particle Acceleration in
Cosmic Plasmas. As reported at these meetings, the high energy gamma
radiation from the June 11, 1991 solar flare is of great interest. Gamma rays
in excess of 1 GeV were seen. Work in preparation for the January AAS meeting
continues.
BATSE
-----
As of December 9th, BATSE has detected 192 cosmic gamma-ray bursts
out of a total of 1049 on-board triggers in 232 days of operation.
There have been 307 triggers due to solar flares with emission
above 60 keV.
A list of the BATSE trigger times for solar flares is available on
the BATSE News Service, which can be reached by logging into SPAN
node BATSE as BNEWS.
During Viewing period 1-16 (12 Dec - 27 Dec), BATSE folded on board pulsar
data will be collected for the Crab Pulsar, Cen X-3, PSR 540-693,
PSR 1509-58, and Her X-1.
COMPTEL
-------
COMPTEL instrument status is unchanged since the last report. A COMPTEL
team meeting is in progress at MPE in Garching, Germany (near Munich). A
major task at the meeting has been a reassessment of the instrumental
background, and the adoption of a "standard background model" for routine
data analysis. A total of 10 contributed talks and 1 invited review talk will
be presented by the collaboration at the January AAS meeting in Atlanta.
Observations of the Crab pulsar totalling 1 month have now been analyzed.
The mean light curve from 1-10 MeV is similar to that observed in high-
energy X-rays. A study of possible temporal variability of pulsed emission
from the Crab is in progress. The Vela Pulsar is not detected at present
limits. Preliminary evidence has been obtained for the 1.8 MeV line of
radioactive aluminum in the region of the Galactic Center.
OSSE
----
OSSE continues to operate well. With Tape Recorder B operation, the telemetry
error rate remains acceptably low.
For the 15 day Viewing Period 16, OSSE will be observing the galactic center
region as its primary target and a joint observation of NGC 253 and NGC 7582 as
its secondary target. The OSSE observation strategy for the galactic center
during this period duplicates the observations acquired during viewing
period 5. In addition, the Sun will be passing near the galactic
center during this observation and so OSSE will also collect high time
resolution spectral and pulsar data in response to BATSE solar flare triggers.
For those days when the Sun is not adequately observed by OSSE observations
of the galactic center and associated background fields, OSSE pointing will
be modified to provide solar coverage for 1000 second periods in response
to BATSE solar triggers.
Posted by:
Tom McGlynn
Compton Observatory Science Support
Center
Internet: [email protected]
SPAN: GROSSC(17565)::mcglynn
|
| 636.40 | Compton Status Report 12/23/91 | PRAGMA::GRIFFIN | Dave Griffin | Fri Jan 03 1992 19:03 | 53 |
| ARTHUR HOLLY COMPTON GAMMA RAY OBSERVATORY
MONTHLY STATUS REPORT
December 23, 1991
NASA's Goddard Space Flight Center-managed Compton Gamma Ray
Observatory (Compton) spacecraft and its instruments continue to
perform well.
Compton is in normal pointing mode with solar arrays pointed
toward the Sun. The observatory is oriented with the +Z axis
pointed at the binary star SCO X-1. As of December 19, Compton
was in an orbit with an apogee of 268.7 miles (432.5 kilometers),
and a perigee of 262.1 miles (422 kilometers), period of 93.1
minutes, and inclination of 28.5 degrees.
The Goddard flight operations team reports the observatory is
functioning well. Tape Recorder B is now the primary recorder
for mission data, supplemented with realtime data. This change
was made November 26, 1991 when the number of bit errors detected
in Tape Recorder A rose to a level above the acceptable range.
Tape Recorder A will be used as a backup, and its performance
will continue to be monitored. Since the changeover to Tape
Recorder B, which shows an acceptably low error rate, the error
rate in Tape Recorder A has decreased by 25 to 40 percent.
Goddard's Energetic Gamma Ray Experiment Telescope (EGRET) is
performing normal operations for the science mission. EGRET
operations continue to run better than expected, according to
project officials.
The Burst And Transient Source Experiment (BATSE) continues to
perform exceptionally well, according to scientists at the
Marshall Space Flight Center, Huntsville, AL. As of December 16,
BATSE had detected 197 cosmic gamma-ray bursts. The source of
these bursts remains a mystery.
The Imaging Compton Telescope (COMPTEL) continues to operate
normally, the scientists at the Max-Planck Institute, Germany,
reported.
The Oriented Scintillation Spectrometer Experiment (OSSE),
managed by the Naval Research Laboratory, Washington, DC, is
performing normal operations for the science mission. The OSSE
instrument also continues to operate well.
The next Compton maneuver will be to the 17th scheduled phase-
one target, Supernova 1987 A, planned for December 27. This
observation holds special significance for the scientific team
because it will help either to prove or disprove theories about
the decay of radioactive material in the wake of a stellar
explosion. One theory is that the reason optical telescopes
notice a leveling-off of the rate of dimming in the supernova
remnant is because radioactive decay is fueling the visible
emissions. Because gamma rays are emitted during radioactive
decay, Compton is the ideal instrument to search for this
evidence.
The Compton Observatory is managed and operated by Goddard for
NASA's Office of Space Science and Applications.
|
| 636.41 | Gamma Ray Observatory Makes New Science Discoveries | PRAGMA::GRIFFIN | Dave Griffin | Tue Jan 14 1992 19:38 | 106 |
| Michael Braukus
Headquarters, Washington, D.C. January 14, 1992
John Loughlin II
Goddard Space Flight Center, Greenbelt, Md.
RELEASE: 92-6
NASA's Compton Gamma Ray Observatory found three new gamma-ray
quasars, detected more than 200 cosmic gamma ray bursts and captured the
best ever observation of the glow of gamma radiation from the disk of the
Milky Way galaxy.
Dr. Carl Fichtel, Goddard Space Flight Center, Greenbelt, Md.,
Principal Investigator for the Energetic Gamma Ray Experiment Telescope
(EGRET), one of four instruments on the Compton Observatory, says his
instrument appears to have detected "still more distant and very luminous
gamma-ray sources, even more distant than the massive quasar 3C 279."
The EGRET team reported three sources of intense localized gamma
radiation, quasars Q0208-512, 4C38.41 and PKS0528+134, detected
between May 16, 1991 and Sept. 18, 1991, located in the constellations of
Eridanus, Hercules and near the Crab Nebula, approximately 10 to 20 billion
light years from Earth.
"The sources are emitting an extraordinary flux of gamma rays, each
gamma-ray photon with an energy greater than 100 million electron volts.
In contrast, a visible light photon has an energy of only a few electron volts,
and an X-ray photon has an energy of 1000 electron volts." Fichtel said,
"The luminosity or total energy emitted by these sources is approximately
10 to 100 million times the total gamma-ray emission of the Milky Way
galaxy."
In addition to the quasar observations, EGRET scientists released an
image today of the June 11, 1991, solar flare made by the telescope. "It is
very unusual to see the high energy gamma-ray emissions from a solar flare,"
Fichtel said. "We were very surprised by this observation."
Dr. Gerald Fishman, Principal Investigator for the Burst and Transient
Source Experiment (BATSE), reports that his team has detected more than
200 cosmic gamma-ray bursts since Compton's launch. BATSE is designed
to study the mysterious phenomenon of gamma-ray bursts.
BATSE scientists announced last September indications of an apparent
random distribution of the bursts in the sky. More recent observations by
the BATSE team have further confirmed the earlier observation with almost
twice as many bursts as the original report.
In addition to their work on the enigmatic gamma-ray bursts, BATSE
scientists have revealed the presence of gamma-ray pulses from a previously
known radio and x-ray pulsar. The object is known as PSR 1509-58 or the
Circinus Pulsar. "This is only the third known example of a gamma-ray
pulsar and only the second one to be observed in the low energy gamma-ray
region," Fishman said.
Pulsars are rotating neutron stars which are thought to be formed
from the core of a massive exploding star or supernova. A neutron star is
composed of super dense matter, a cubic centimeter (about the size of an
ordinary sugar cube) which would weigh over 10 million tons. Scientists
theorize that a neutron star, only 10 miles in diameter, would have about 1-
1\2 times the mass of Earth's sun.
The Oriented Scintillation Spectrometer Experiment (OSSE)
captured, in September of this year, the best ever observation of the glow of
gamma radiation from the disk of the Milky Way galaxy. The glow was
caused by matter and antimatter annihilating each other.
"OSSE continues to operate very successfully. During the first nine
months of the mission, OSSE has achieved excellent observations of several
galactic sources as well as a number of other galaxies that may be associated
with the centers of these distant galaxies," according to Dr. James Kurfess
Principal Investigator for OSSE, Naval Research Laboratory, Washington, D.C.
"OSSE has shown, with unprecedented sensitivity, the gamma-ray
glow from matter-antimatter annihilation. One surprise is that the
observations are not providing strong evidence that the emissions may be
coming from some unknown compact objects located somewhere toward
the center of the galaxy," Kurfess said.
OSSE also has acquired observations of many solar flares, often
following a solar flare trigger signal from the BATSE which results in an
automatic re-pointing of OSSE's detectors toward the sun.
The Imaging Compton Telescope (COMPTEL) continues to operate
very well. "We are extremely pleased with the operation of our instrument,
and we currently are making a very accurate gamma-ray map of our galactic
plane," according to COMPTEL Principal Investigator Volker Schoenfelder,
Max Planck Institute, Germany.
"The overall operation of the observatory has been nothing short of
superb," according to Paul Pashby, Project Manager, Goddard Space Flight
Center, Orbiting Satellite Project. Pashby went on to say that the massive
observatory "is extremely responsive and a joy to work with."
The Compton Observatory, built by TRW Inc., Redondo Beach, Calif., is
the second of NASA's "Great Observatories." The first was the Hubble Space
Telescope, launched in April 1990. The third will be the Advanced X-ray
Astrophysics Facility, expected to be launched in 1998.
Deployed April 7, 1991, from the Space Shuttle Atlantis, Compton
currently orbits Earth at an altitude of 268 by 262 miles. The Compton
Observatory was developed and is managed and operated by Goddard Space
Flight Center, Greenbelt, Md., for NASA's Office of Space Science and
Applications.
|
| 636.42 | Update - January 16 | MTWAIN::KLAES | All the Universe, or nothing! | Wed Jan 22 1992 16:02 | 150 |
| Article: 19746
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #48
Date: 21 Jan 92 21:09:37 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #48
Thursday, January 16, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
This report is slightly late due to the AAS meeting ending yesterday
afternoon.
Normal science operations continues using the B Tape Recorder. However,
the error rate of the B Tape Recorder has shown a significant rise
since the maneuver of January 10. Recent days show approximately 1000
bit slips per day in the OSSE data, out of 42,000 2-second data packets.
The project is proceeding to implement an error detection software
method that can correct errors, within limits, at the minor frame level
(33 msec).
Only an OSSE instrument reports has been received this week, due to the AAS
meeting. The following is my summary of Compton science reports from the
AAS meeting in Atlanta. I will try to add more next week.
Dr. Fishman reported the discovery of a new gamma-ray pulsar, by BATSE, only
the second pulsar (after the Crab) to be seen in the low energy gamma-ray
energy range. The pulsar is PSR 1509-58, also known as the Circinus
pulsar. This pulsar has been previously seen in the radio and as a
soft X-ray source. It has a period of about 150 msec.
Several papers were presented by the BATSE Team members on the isotropy
and intensity distribution of gamma-ray bursts. An initial paper on this
has now appeared in Nature (vol 335, p 143, Jan 9, 1992). In confirmation
of their earlier reports, they see no evidence of any galactic plane
preference or avoidance for gamma-ray bursts; at Atlanta Dr. Horack
showed distributions for subdivisions of bursts sorted by morphology
(simple spikes, complex spikes, smooth), and by brightness, but none
of the divisions was claimed to show a significant galactic dipole moment.
Dr. Meegan showed the log N/log S plot which appears in Nature. The
curve does not approach a slope of -3/2 at fainter bursts, but appears
to go to -0.8 or so within the range of their data.
Dr. Teegarden reported on the search for line features in BATSE burst spectra.
Thus far, 25 bursts had sufficiently good spectroscopy detector data for
close examination. Their detection criterion was that a feature be seen
simultaneously in data from two of the 8 BATSE detectors. No line features
have been found. The discrepancy with earlier reports of lines by other
experimenters is still only a 1-sigma effect or so, so it cannot be said that
the BATSE data is in contradiction to the existence of lines in some bursts.
Drs. Band and Kippen of BATSE reported a hard-to-soft trend in the spectrum
within bursts, both within an individual spike and for the burst as a whole.
Dr. Finger reported on monitoring of the intensity and phase variations of the
Cen X-3 X-ray pulsar by BATSE. He sees light variations on several different
timescales including weeks to months, and phase wandering of the pulse by
approximately 50 pulse-widths total over the about 6 months of data.
The EGRET Team reported the discovery of 3 new AGN sources: Q0208-512, 4C38.41,
and PKS0528+134. These are at redshifts z=1.0, 1.8 amd 1.9, respectively.
They are not especially remarkable AGN's, and would not necessarily have
been expected to be the brightest sources in that part of the sky so far
surveyed. The spectral index of 4C38.41 was -1.82.
EGRET also reported on the rapid variations in brightness of 3C279 during
their viewing this year. During 2 weeks in June, the source brightened by
a factor of 4 over 11 days, then dropped by the same amount over the next
2 days. The October measurements showed essentially no variation over 2
weeks, at about the lowest brightness of the June data. Both periods
showed a spectrum with index of -1.8 to -2.0.
EGRET showed the distribution of six spark-chamber events from the GRB
event of May 3.
Data from OSSE, COMPTEL and EGRET was presented together for the pulsed
component of the Crab spectrum, which is about 25-35% of the total Crab
intensity at 1-10MeV, according to COMPTEL. No break is seen in the range
covered, up to about 5 GeV. By comparing this spectrum to the pulsed-
component intensity given at 400 GeV by the Whipple observatory, there must
be a break in the 5-400 GeV range somewhere, as the continuation of the
Compton data lies a factor of 100 above the Whipple point.
COMPTEL reported their data on the spectrum and pulse shape of 3C273.
They also detected 3C279. As a 4-5 sigma detection it is weak but definite.
For supernova 1991T, both OSSE and COMPTEL reported only upper limits to
the intensity. Similarly for SN1987A by OSSE.
Note the report of a new source, Cen A, in the OSSE section below. The
OSSE Galactic-center 511 keV scans show a narrow band of emission in the
galactic plane, with a relatively broad distribution along the plane. They
said the model based on the distribution of novae fits best to their data.
COMPTEL
OSSE
----
OSSE continues to operate well. Detector 4 motion was stopped for about 5
hours, from 1700 UT to 2200 UTY on January 10, as a result of noise on the
main potentiometer. The noise was probably related to the calibration of
detector 4 at its X reference position, which took the potentiometer wipers
to largely unused parts of the resistive track, where the wipers may have been
contaminated. However, apart from two brief noisy episodes in that 5 hours,
the potentiometer readout has been stable and accurate, and detector 4 is now
performing normally. In addition, the detector 4 redundant potentiometer, which
has had a large offset with respect to the main potentiometer since launch, was
brought back to approximate aggreement with the main potentiometer by the
calibration, but is still considered unreliable.
Since the last maneuver of CGRO on January 10, the telemetry error rate seen
by OSSE has increased 5-fold, from 200 to 1000 errors per day. This indicates
that Tape Recorder B is deteriorating in the same way as Tape Recorder A, and
is becoming almost as bad as Tape Recorder A. The OSSE team strongly urges that
solutions to the problem be pursued and implemented by the project as soon as
possible. The OSSE team is currently working with the CGRO Flight Operations
Team to implement a post-PACOR fix to the telemetry, where the FOT provides
bit-slip error identifications and correction data for 24 hour periods, which
are transferred to OSSE over the Internet. We recommend project support for
this method until any solution provided by PACOR can be demonstrated to be as
effective.
Between January 10 and January 15, OSSE has responded to BATSE solar flare
triggers with slews to the Sun on 1 occasion, at Truncated Julian Day number
8636.530. This trigger was not related to any apparent GOES flare.
Several members of the OSSE Science Team attended the AAS meeting this week
and four OSSE papers will be given at the Workshop on X-ray Signatures of
Neutron Stars and Black Holes next week. Preliminary spectal results and
some temporal characteristics of several sources were presented, including
the Crab Nebula and the Crab pulsar, the galactic sources Cyg X-1 and
GX339-4, the 0.51 emission for the galactic center region, the AGN's Cen A,
NGC 4151, 3C273 and 3C279. The preliminary results from the first 8 weeks
of observations of the galactic center region do not indicate any strong
evidence for variability in 0.51 MeV emission consistent with the energy
resolution of the OSSE instrument. This includes the period from 3-17 Oct
1991 during which time preliminary data from SIGMA indicated a weak turn-on
of the source 1E1740.7-2942.
Posted by:
Tom McGlynn
Compton Observatory Science Support Center
Internet: [email protected]
SPAN: grossc(17565)::mcglynn
|
| 636.43 | Update - January 23 | MTWAIN::KLAES | All the Universe, or nothing! | Fri Jan 24 1992 12:48 | 209 |
| Article: 19822
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #49
Date: 23 Jan 92 22:04:42 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #49
Thursday, January 23, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Normal science operations continues using the B Tape Recorder. The error
rate does not create a serious problem in data processing at the moment.
A maneuver was performed this morning to the attitude for period 19
(Z axis near BII= 58, LII = -43, OSSE primary target is galactic plane at
58 degrees, OSSE secondary is Her X-1). The maneuver took place from 1334Z
to 1414Z, and covered an angle of 132 degrees.
Scientists from all of the Compton Teams are presenting results of their
observations at the "X-Ray and Gamma-Ray Signatures of Black Holes versus
Neutron Stars" meeting in Aspen, CO this week.
BATSE
-----
Discovery of the binary motion of OAO 1657-41 was announced last week
at the AAS meeting and in IAUC 5430. Here is the relevant text from the
IAU circular:
OAO 1657-415
M. H. Finger, Computer Sciences Corporation; D. Chakrabarty, J.
M. Grunsfeld, and T. A. Prince, California Institute of Technology;
R. B. Wilson, G. J. Fishman, and C. A. Meegan, Marshall Space Flight
Center, NASA; and W. S. Paciesas, University of Alabama at Hunts-
ville, report for the BATSE team: "As part of a joint MSFC/Caltech
pulsar detection and all-sky monitoring program, Fourier transform
analysis is performed daily on the Compton Observatory BATSE dis-
criminator rates (1.024-s resolution, 20-60 keV). OAO 1657-415 has
been detected repeatedly over the last 6 months in about 1-day
Fourier transforms. The resulting frequency history over this time
span shows a clear modulation due to binary orbital motion. Prelim-
inary analysis provides an orbital period of 10.4 +/- 0.1 days and
projected semimajor axis of 95 +/- 5 light seconds. The pulse peri-
od in the pulsar frame is 37.667 +/- 0.005 s on 1991 Oct. 20 UT.
The pulsar is observed to be eclipsed by its binary companion and
analysis indicates that the orbit is eccentric. Further analysis
and observations are in progress."
1992 January 15 Daniel W. E. Green
As of January 21th, BATSE has detected 217 cosmic gamma-ray bursts
out of a total of 1202 on-board triggers in 275 days of operation.
There have been 398 triggers due to solar flares with emission above
60 keV.
During Viewing period 1-19, BATSE folded on board pulsar data will
be collected for the Crab Pulsar, PSR 0540-69, PSR 1259-63, SMC X-1,
and PSR 1509-58.
In addition to the items reported last week, BATSE presentations at the
AAS included:
Dr. Paciesas presented a study of the correlation of Burst hardness
ratios with peak flux. No strong correlations were evident.
Dr. Harmon reported on the BATSE occultation measurement program, and
the occultation observations of the transient GX339-4. Dr. Skelton
of JPL reported progress on enhancing the occultation technique.
Dr. Grunsfeld of Caltech reported on a pulsar detection and all-sky
monitoring program based on daily fourier transforms of the BATSE
discriminator rates (1.024-s resolution, 20-60 keV).
COMPTEL
-------
Normal COMPTEL operations continue. After the spacecraft maneuver just
completed the Sun is once again within the field of view of the instrument.
During Observing Period 19 the solar observing mode of COMPTEL will be enabled,
and the instrument will respond to solar flare triggers received from BATSE.
BATSE reported that a gamma-ray burst occurred within COMPTEL's field of view,
at an experiment zenith angle of 25 degrees, on 13 January (=TJD 8634). A search
for MeV-emission from this event is underway. COMPTEL has noted in recent
"quick-look" data received from PACOR a significant increase in the rate of bit
errors from Tape Recorder B on the spacecraft.
EGRET
-----
I inadvertently failed to include last week's EGRET report as it was
submitted to me. Here is their report:
There was a power glitch at the EGRET ground operations center on January 12,
1992 that caused several difficulties. The X.25 network was damaged. Some
of the SUN and Tektronics equipment was affected as well. Repair work was
in progress for several days after then. Much of the equipment was
functioning by January 16, with the remainder soon after. Naturally, the
data reduction work was slowed during this period. The instrument performance
remains the same. At the moment, the data quality remains acceptable; however,
there is concern about the increasing error rate of the B tape recorder. Also,
there is still concern about the absolute time determination.
The following sumarizes the papers presented at the AAS Meeting in Atlanta,
and the IAU telegrams. The papers and lead authors were:
David Thompson EGRET High Energy Gamma-Ray Observations of the
May 3, 1991, Gamma Ray Bursts
Robert Hartman High Energy Gamma Radiation from Quasar 3C 279
Detected by the EGRET Telescope on the Compton
Gamma-Ray Observatory
Carl Fichtel (invited) The Preliminary Results from the High Energy Gamma-
Ray Telescope on GRO
Donald Kniffen EGRET Observations of the Crab and Vela Pulsars:
Preliminary Gamma-Ray Light Curves
Patrick Nolan EGRET Observations of the Crab and Vela Pulsars:
Preliminary Pulsed Spectra Above 100 MeV
John Mattox EGRET High Energy Gamma-Ray Observations of Cygnus X-3
IAU Circular 5431:
3C 279
The Compton Observatory/EGRET Team (G. Kanbach, H. A. Mayer-
Hasselwander, C. von Montigny, K. Pinkau, H. Rothermel, and M.
Sommer, Max-Planck-Institut fur Extraterrestrische Physik; D. L.
Bertsch, C. E. Fichtel, R. C. Hartman, S. D. Hunter, D. A. Kniffen,
P. W. Kwok, J. R. Mattox, P. Sreekumar, and D. J. Thompson, Goddard
Space Flight Center, NASA; Y. C. Lin, P. F. Michelson, and P. L.
Nolan, Stanford University; and E. Schneid, Grumman Aerospace Cor-
poration) communicates: "The high-energy gamma-ray flux from 3C 279
was observed to be (8 +/- 1) x 10E-7 cmE-2 sE-1 (energy > 100 MeV)
during the period 1991 Oct. 3-17, 30 percent of the flux observed in
the period June 15-28 (IAUC 5311). Also, further analysis of the
1991 June observation indicates highly significant time variation of
the 3C 279 flux during the 2-week period (chance of being random
10E-9). After a gradual increase, the flux peaked on June 25 and
then sharply decreased over the following three days it was observed.
We note that EGRET will be pointed 34 deg from 3C 379 during the pe-
riod 1992 Apr. 16-30. At this angle, the EGRET sensitive area is
down by an order of magnitude, but if the flux level is similar to
that in June, then some sensitivity to time variations remains.
Simultaneous radio and optical observations might be of great value."
4C 38.41, PKS 0528+134, PKS 0208-512
The Compton Observatory/EGRET Team also reports: "EGRET data
analysis reveals highly significant detections of gamma-ray flux
(energy > 100 MeV) for three radio-loud, flat-spectrum sources.
Following are the tentative identification (catalogue designation),
observation dates (1991), and most probable position (galactic coor-
dinates in degrees, system II) with a 63-percent confidence region:
4C 38.41, Sept. 12-19, l = 61.0 +/- 0.3, b = 42.30 +/- 0.16; PKS
0528+134, Apr. 22-May 30, l = 191.34 +/- 0.15, b = -10.95 +/- 0.10;
PKS 0208-512, Sept. 19-Oct. 3, l = 276.16 +/- 0.25, b = -61.99 +/-
0.13."
1992 January 15
Report for January 23:
EGRET operation remains normal. The December gas fill is holding up well.
The only concern at present is the increasing error rate from Tape
Recorder B. The error processing via the test correction file prepared by
the FOT (Flight Operations Team) is being studied.
More from Atlanta: In his paper on EGRET observations of the Cygnus region,
Mattox reported that the COS-B sources 2CG 078+01 and 2CG 075+00 are
definitely detectable. They are point-like sources as seen with EGRET's
point spread function. No definite detection of Cygnus X-3 was claimed,
either as a constant or periodic source.
OSSE
----
OSSE continues to operate well. For the GRO Phase 1 viewing period 19, which
starts on January 23, the primary OSSE target will be the galactic plane at
galactic longitude 58 degrees, and the secondary OSSE target will be Her X-1.
In addition, OSSE will be operated with the Charged Particle Detector veto
disabled in each detector during those times when neither primary nor secondary
targets are visible to OSSE, to use cosmic ray protons as a high energy
calibration source for the detectors.
The error rate on Tape Recorder B continues to be excessively high, with
approximately 1300 errors per day. The OSSE Team is working with the FOT to
develop ground correction procedures for these errors.
Between January 15 and January 20, OSSE has responded to BATSE solar flare
triggers with slews to the Sun on 1 occasion, at Truncated Julian Day number
8636.530. This trigger was not related to any apparent GOES flare.
Several scientists from the OSSE Team are presenting results of OSSE
observations at the "X-Ray and Gamma-Ray Signatures of Black Holes versus
Neutron Stars" meeting in Aspen, CO this week.
Posted by:
Tom McGlynn
Compton Observatory Science Support Center
Internet: [email protected]
SPAN: GROSSC(17565)::MCGLYNN
P.S., Unless I receive some advice to the contrary, I'll continue
to post these here in sci.astro rather than sci.space.news. Nominally
the focus of these reports is the science of the mission rather than
the spacecraft, though that certainly is important.
|
| 636.44 | Update - February 13 | VERGA::KLAES | All the Universe, or nothing! | Fri Feb 14 1992 17:02 | 111 |
| Article: 20335
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #52
Date: 14 Feb 92 15:21:00 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #52
Thursday, February 13, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Normal science operations continues using the B Tape Recorder.
The OSSE Team has submitted a request, as noted in the OSSE section below,
to modify the spacecraft timeline for periods 22, 24 and 25 in order to
observe the Galactic Center and NGC 4151. The changes can be summarized
in this table: (Coordinates in RA,DEC)
Period Dates Current Proposed
Z-axis OSSEPrim OSSESec Z-axis OSSEPrim OSSESec
22.0 5-12 Mar 209,+71(~MRK279) MRK279 M31 209,+71(~MRK279) MRK279 M31
22.5 12-19 Mar 209,+71(~MRK279) MRK279 M31 211,+71(~MRK279) NGC4151 M279
24 2-16 Apr 1,+20(~MRK335) MRK335 VelX-1 225,+9 GalCtr none
25 16-30 Apr 223,+11 4U0115+634 none 1,+20(~MRK335) MRK335 VelPSR
Observers planning coordinated observations of any affected periods should
take note, and may wish to send comments. This change is not final yet,
but may be soon.
BATSE
-----
As of February 10th, BATSE has detected 232 cosmic gamma-ray bursts
out of a total of 1279 on-board triggers in 295 days of operation.
There have been 431 triggers due to solar flares with emission above
60 keV.
A listing of BATSE gamma-ray burst Cmax/Cmin (peak count rate/ trigger
threshold count rate) values is being posted on the BNEWS electronic
news service. This listing includes burst up to the end of January.
Over the SPAN network log in to node BATSE with login name BNEWS in order
to obtain the listing and other BATSE related information.
A program to correct the tape-recorder induced errors in the BATSE data
is now operational. The corrected error fraction is approximately 95%.
COMPTEL
-------
The COMPTEL operations group continues to monitor the performance of one of the
lower detector modules of the instrument. To date, the occasional suspect
behavior of this module has had no impact on the science data collected from
the instrument. Continued close observation of this module will be maintained.
A clarification: the software bug recently uncovered in the COMPTEL analysis
software, referred to in last week's report, was in a coordinate transformation
routine within the pulsar analysis subsytem. The error was quadrant-dependent,
and has NO effect on the determination of pulsed emission from the Crab, or on
other preliminary scientific results previously announced by the team.
EGRET
-----
EGRET operations remain normal. The rate of data reduction remains good.
The tape recorder error rate on the B recorder is about 3% now (i.e.
of the EGRET (2.048 second) packets, 3% contain at least one error). For
the short period when the tape recorder A was on this week, the bit
rate was much higher, over 10%. Final testing and documentation on the
software to remove bit errors is nearly finished, and we hope to be using
it in a few days.
The EGRET Team feels that the absolute time problem meeting held on
Feb 10 by Dave Bertsch was a very profitable one, and the Team will
support the work in any way possible. They recommend looking to see
if any other satellite in low earth orbit, either classified or
unclassified, can make simultaneous observations of cosmic or solar
bursts to obtain coordinated timing measures.
OSSE
----
OSSE continues to operate well. The OSSE mission operations team is continuing
to refine its use of the CGRO tape recorder bitslip correction files provided
by the GRO Flight Operations Team.
Since February 6, OSSE has been configured to slew to the Sun in response to
BATSE solar flare triggers and has done so on Truncated Julian Days 8659.155,
8660.140, 8660.384, 8661.986.
OSSE has recently proposed some changes to the CGRO Phase 1 viewing plan, to
provide OSSE with an observation of the galactic center in viewing period 24
(Apr 2-Apr 16) in possible coordination with the Australian balloon campaign and
SIGMA, and to provide OSSE with an observation of NGC 4151 following reports
that it was recently in a high state of emission. These objectives would be
accomplished by splitting viewing period 22 into two 1-week observations with
a yaw maneuver of CGRO to observe NGC 4151 in the second week, and with a swap
of viewing periods 24 and 25 with a GRO maneuver to allow OSSE to observe the
galactic center in the resultant period 24 and with OSSE observing the Vela
pulsar in the resultant period 25.
Posted by:
Tom McGlynn
Compton Observatory Science Support Center
[email protected]
|
| 636.45 | CGRO Monthly Status Report - January 1992 | PRAGMA::GRIFFIN | Dave Griffin | Fri Feb 14 1992 18:53 | 83 |
| ARTHUR HOLLY COMPTON GAMMA RAY OBSERVATORY
MONTHLY STATUS REPORT
February 12, 1992
NASA's Compton Gamma Ray Observatory (Compton) spacecraft and
its instruments continue to perform well.
Compton is in normal pointing mode with solar arrays pointed
toward the Sun. The observatory is oriented with the +Z axis
pointed at the 20th scheduled Phase I target, the X-ray binary
star SS 433. A 173-degree maneuver to this target was performed
on February 6, 1992.
As of February 6, Compton was in an orbit with an apogee of
264 miles (424.8 kilometers), perigee of 258 miles (414.6
kilometers), period of 93.0 minutes, and inclination of 28.5
degrees.
Dr. Carl Fichtel, of Goddard, co-principal investigator for
the Energetic Gamma Ray Experiment Telescope (EGRET) aboard
Compton Observatory, reports that the rate of EGRET data analysis
remains good.
Burst and Transient Source Experiment (BATSE), scientists
report that BATSE has detected more than 228 cosmic gamma ray
bursts since Compton's launch, April 5, 1991. Dr. Gerald
Fishman, of NASA's Marshall Space Flight Center is principal
investigator for BATSE.
The primary Oriented Scintillation Spectrometer Experiment
(OSSE) target for this viewing period will be a combined
observation of the X-ray binary star SS 433 and an observation of
the galactic plane. OSSE's secondary target will be the
cataclysmic variable star NGC 253. Dr. James Kurfess is principal
investigator for OSSE, Naval Research Laboratory, Washington D.C.
The Imaging Compton Telescope (COMPTEL) continues to operate
nominally. COMPTEL scientists were pleased to announce the
detection of the Vela pulsar.
This past week a software "bug" was uncovered in the COMPTEL
analysis computer software which had a detrimental effect on
previous searches for Vela. The discovery of the bug led
scientists to re-analyze previous data sets, and Vela is now seen
to pulse throughout COMPTEL's energy range. These data have led
to the first-ever map of the Vela pulsar in the 10-20 MeV energy
range.
COMPTEL is operating at 73 percent of its maximum efficiency
with 6 of 7, D1 detectors; and 12 of 14, D2 detectors operating.
COMPTEL principal investigator is Volker Schoenfelder, Max Planck
Institute, Germany.
The Goddard flight operations team reports the observatory is
functioning nominally. Tape Recorder B is now the primary
recorder for mission data, supplemented with realtime data.
Goddard engineers, using a combination of computer hardware
and software, have devised a strategy to correct the data errors,
which are contained in the telemetry bit stream. Current
development plans indicate that a procedure for error correction
could be available for use in late March or early April. In
addition, the Flight Operations Team has developed an interim
procedure to provide each scientific investigator with a data
file which identifies the location of correctable errors.
Investigators can use this data file to help in the editing
process. With this method the Flight Operations Team generates
daily repair files for data provided on tape from all tape
recorder dumps. The repair files are transmitted electronically
to the instrument teams who may perform their own error
correction.
Since January 30, OSSE has been using the repair files,
resulting in a reduction in the total error count in the OSSE
telemetry from more than 1000 errors per day to about 30 errors
per day. BATSE and EGRET are nearing the completion of the
testing phase of their software to utilize the repair files and
COMPTEL is using a listing of the errors from the repair files to
separate valid data from the data errors in the quick-look data.
Meetings to determine the cause of these data errors are
scheduled to take place this week at the Odetics facility,
manufacturer of the tape recorders, in Anaheim, CA.
Following these meetings, a test plan will be prepared and
tests with an engineering model will be conducted.
The next Compton attitude maneuver will be to the 21st
scheduled Phase I target, the active galactic nucleus NGC 1068.
The maneuver is currently planned to begin during the Tracking
and Data Relay Satellite contact on February 20, 1992.
The Compton Observatory is managed and operated by the Goddard
Space Flight Center for NASA's Office of Space Science and
Applications.
-GSFC-
|
| 636.46 | Update - February 20 | VERGA::KLAES | All the Universe, or nothing! | Mon Feb 24 1992 17:57 | 156 |
| Article: 20511
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #53.
Date: 21 Feb 92 22:21:56 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #53
Thursday, February 20, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Normal science operations continues using the B Tape Recorder.
As of February 13, Compton GRO was in an orbit with an apogee of 422.2
kilometers, perigee of 414.1 kilometers, period of 92.9 minutes, and
inclination of 28.5 degrees.
Representatives from the Compton GRO Flight Operations Team (FOT), the
GSFC Flight Data Systems Branch, the GSFC Satellite Servicing Project,
the JPL Magellan Project, and Odetics engineers met at the Odetics
facility in Anaheim, California on February 10-11 to further investigate
the cause of the errors in the data played back from the on-board tape
recorders. A very productive exchange of information occurred. A
number of action items and tests to be performed by the FOT and Odetics
were assigned.
A maneuver was performed this morning to point to the attitude for period
21. The new z-axis is close to NGC 1068 which is the OSSE primary target.
The OSSE secondary target is the galactic center. The maneuver took
place from 1503-1544Z on Feb 20, and covered an angle of 140 degrees.
A constraint violation problem (moon too close to a star tracker) was found
in one portion of the OSSE request to repoint for upcoming periods as reported
last week. The period 24 request which enabled OSSE to observe the galactic
center region from April 2-16 was marginally infeasible. Modifications to
permit the desired science are being developed.
BATSE
-----
As of February 18th, BATSE has detected 239 cosmic gamma-ray bursts
out of a total of 1307 on-board triggers in 303 days of operation.
There have been 443 triggers due to solar flares with emission above
60 keV.
During Viewing period 1-21, BATSE folded on board pulsar data will
be collected for the SMC X-1, the Crab Pulsar, PSR 1509-58, and Her X-1.
The following was submitted as a IAU circular last week:
EXO 2030+375
R. B. Wilson, B. A. Harmon, G. J. Fishman, C. A. Meegan, Marshall Space
Flight Center, NASA; M. H. Finger, Computer Sciences Corporation; W. S.
Paciesas, University of Alabama at Huntsville, T. A. Prince, J. M. Grunsfeld,
and D. Chakrabarty, California Institute of Technology; report for the BATSE
team: Pulsed hard x-ray emission from the transient x-ray pulsar
EXO 2030+375 is being detected by the BATSE instrument onboard the Compton
Observatory. The pulsed emission was first detected in the 20-60 keV band on
February 9th. The pulsed flux has been increasing daily. On February 10th the
pulsations were detected from 25 keV to 100 keV. Approximate fluxes measured,
in units of 10^-5 photons-cm^-2-sec^-1 were: 44. +/- 6.8., 10. +/- 5.1,
5.9 +/- 1.9, and 1.5 +/- 0.9, in the energy ranges 30-40, 40-50, 50-70,
and 70-100 keV, respectively. The spectral index is 3.9 +/- 0.8. The pulse
period has increased steadily at rate of 2.7 ms/day, with the barycentric
period on JD 2448662.5057 being 41.6794 +/- 0.0006 seconds. No binary
corrections have yet been applied, since the orbital phase is unknown.
The source has also been detected using Earth occultation, but the measured
flux of EXO 2030+ 375 is currently not separable from that of Cyg X-3.
The pulsed power in the daily FFTs of the DISCLA data (20-60 keV) peaked
on February 13th at three times the power seen on February 10th. On
February 20th the pulsed power dropped below our (FFT) detection threshold.
Last week, the gains of the spectroscopy detectors were changed to better
concentrate on the low energy region. This will allow a more sensitive search
for cyclotron features in gamma-ray bursts. There are now six detectors
operating at 7x nominal gain and two operating at .4x gain.
Also last week, a PMT calibration and balance procedure was performed on the
LAD PMT's. Only 4 of the 24 LAD PMT's required a significant adjustment. The
long-term stability and performance of the PMT's has been excellent, with
little degradation, if any, noticed since launch. The resolution of all 16
detectors is nominal.
COMPTEL
-------
Preliminary results on the recently-announced detection of the
Vela pulsar by COMPTEL will be presented at next week's meeting
in Taos, New Mexico on Isolated Pulsars. The COMPTEL operations
group continues to monitor the performance of one of the
lower detector modules of the instrument. The increased counting
rates in this module appear to be due to a noisy photomultiplier tube.
Over the past week the COMPTEL team completed its technical review of
COMPTEL-related proposals for guest investigations during Phase 2 of
CGRO observations.
EGRET
-----
EGRET operations remain normal. The software that was developed
by EGRET to remove the bit errors is now ready for use and being
applied. EGRET has fallen about two weeks behind in the data
reduction while this software was being implemented. It should be
possible to return to the previous level of EGRET data processing
over the next few months if no major problems occur. During this
past two weeks the analysts have been studying older high latitude
exposures in more detail to confirm the analysis procedures.
The tape recorder bit error rate seems to be climbing slowly
recently. The EGRET Team supports the project's development of
a plan for maximum real time coverage, should this turn out to be
necessary in the future.
David Bertsch has been serving as chair of the committee to study the
absolute time problem. By direct transmission from the ground to the
spacecraft (not through TDRS) it has been verified that the spacecraft
clock itself is correct. The possibility of incorrect knowledge of the
delay of transferring the clock time information to the instruments still
exists. A recorded burst on another satellite with good absolute time could
resolve the matter. Unfortunately we now know that certain of the other
satellites that we had hoped might have good enough absolute time do not.
There are still two other known possibilities.
The EGRET Team is recommending a review at this time of the studies
and plans for the first reboost of the Compton orbit, to try to develop
a procedure for the reboost effort.
Work is in progress on several scientific papers. Four or more should
be submitted during March.
OSSE
----
OSSE continues to operate well.
For viewing period 21, the OSSE primary target will be the Seyfert galaxy
NGC 1068, and the OSSE secondary target will be the galactic center. Since
the galactic center is only visible to the lower two OSSE detectors, it will be
given priority during those times when both it and NGC 1068 are simultaneously
visible. The slewing of OSSE detectors in response to BATSE solar triggers will
be disabled for viewing period 21.
Since February 11, OSSE has slewed to the Sun in response to BATSE solar flare
triggers on 6 occasions, on Truncated Julian Days 8666.583, 8669.025, 8669.059,
8669.390, 8669.653, and 8670.364.
OSSE scientists have recently completed the technical feasibility reviews of
CGRO phase 2 proposals relevant to the OSSE instrument, in preparation for
the scientific peer review of CGRO phase 2 proposals.
Posted by: Tom McGlynn
Compton Observatory Science Support Center
[email protected]
|
| 636.47 | Update - February 27 | VERGA::KLAES | All the Universe, or nothing! | Tue Mar 03 1992 17:07 | 117 |
| Article: 20657
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #54.
Date: 28 Feb 92 15:48:39 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #54
Thursday, February 27, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Normal science operations continues using the B Tape Recorder.
As of February 20, Compton GRO was in an orbit with an apogee of 421.1
kilometers, perigee of 413.1 kilometers, period of 92.9 minutes, and
inclination of 28.5 degrees.
Error Correction: The interim off-line method for error correction continues
to be very useful to the instrument teams. In addition to OSSE and
BATSE, EGRET is now using the daily repair files operationally.
Note the comments in the OSSE report below: A request is under consideration
to modify the planned pointing for period 22 (2-Mar to 19-Mar) to
observe Nova Cyg 1992 as an OSSE target for this entire period, while
leaving the z-axis close to its current planned location near MRK 279.
BATSE
-----
As of February 27, BATSE has detected 244 cosmic gamma-ray bursts
out of a total of 1349 on-board triggers in 312 days of operation.
There have been 450 triggers due to solar flares with emission
above 60 keV.
BATSE Co-Investigator Robert Wilson is attending the Workshop on
Pulsars in Taos, where he is presenting BATSE data on the Crab and
Circinus pulsars.
The ground fix for tape recorder errors has been in operation for
about a week. About 95% of errors are corrected; however, the
rate of uncorrected errors continues to rise at an alarming rate.
BATSE continues to operate nominally. No changes have been made
since the last report.
The BATSE observations of the source EXO 2030+375, reported last week,
were announced in IAU Circular 5454, dated Feb 20, 1992.
COMPTEL
-------
The COMPTEL operations group continues to monitor closely the performance of
the lower detector modules of the instrument. There is some indication that
occasional anomalous counting rates noted in one module may be
temperature-dependent. There will be a COMPTEL team meeting at the Laboratory
for Space Research in Leiden, Holland next week. Among the topics to be
discussed are the scientific presentations by the collaboration at the upcoming
meeting on High Energy Astronomy in Toulouse, France. There are currently one
invited and 10 contributed talks and poster papers scheduled for presentation
by the team. This week COMPTEL supported the peer review of proposals received
for the Compton GRO Phase 2 Guest Investigator program, held at NASA Goddard
Space Flight Center.
EGRET
-----
EGRET operations remain normal. The error correcting software
developed by Nancy Laubenthal for EGRET is in place and operating
well. Flight gamma ray data is now being processed in the regular
manner. Data reduction is proceeding smoothly again. The bit error
rate seems to be climbing very slowly at this time.
Regarding the absolute time problem, following Dave Bertsch's lead,
several people, including Gottfried Kanbach and Tom Cline, have
reported absolute error determinations based on bursts observed on
other satellites. Although the uncertainties are large, all are
consistent with an error of one and a half to three seconds in the
same direction. It is hoped that the error may be determined to
within tens of milliseconds even if the source of the error in the
Compton Observatory system cannot be found.
An IAU telegram was submitted reporting the detection of a sixth
quasar by EGRET. We are anxious to see if the very high energy
ground based telescopes see any of these quasars.
OSSE
----
For viewing period 22, which starts on March 5, the OSSE team had proposed two
separate one week observations, to include a one week observation of NGC 4151.
However, since the brightest classical nova in 17 years, N Cyg 1992 (IAUC 5454)
has recently appeared and meets the pre-launch requirements for an OSSE target
of opportunity, the OSSE team has proposed that all of viewing period 22 be
used to observe N Cyg 1992, with MRK 279 as the Z-axis OSSE target. This
observation could be accomplished with a 3 degree change in the position of the
GRO Z-axis, which slightly improves the overall sky coverage for the Phase 1
viewing plan. At the present time, this proposed OSSE target of opportunity is
being considered by the project.
OSSE continues to use the tape recorder bitslip daily repair files provided by
the GRO Flight Operations Team. The number of telemetry packets not repaired by
this process has risen significantly since the production of the repair files
started, to several hundred errors per day. This rate of increase is faster
than the rate of increase of total tape recorder errors per day, which is now
around 4000 per day for tape recorder B. The OSSE team recommends that this
problem with providing fixes for tape recorder errors be investigated and
solved, if the tape recorders are to remain usable on GRO.
Between February 18 and February 20, OSSE has slewed to the Sun in response to
BATSE solar flare triggers on 3 occasions, on Truncated Julian Days 8670.364,
8671.159, and 8672.538. The slewing of the OSSE detectors to the sun in response
to BATSE solar flare triggers was disabled on February 20.
Posted by: Tom McGlynn
Compton Observatory Science Support Center
[email protected]
|
| 636.48 | Updates - March 5 and 12 | VERGA::KLAES | All the Universe, or nothing! | Mon Mar 16 1992 17:12 | 376 |
| Article: 20983
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #55
Date: 13 Mar 92 15:33:56 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #55
Thursday, March 5, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Normal science operations continues using the B Tape Recorder.
In addition to the bit-slip errors, bit-flip errors which are not
correctable with the error-correction algorithm currently in use have
begun to occur in the data at a relatively low rate. An effort is underway
to try to develop an algorithm for correcting these errors as well.
Intensive studies are underway to try to understand the cause of the
Tape Recorder errors. Some theories are being looked at but none is
accepted at this time.
A maneuver was performed this morning, to the attitude for Period 22,
which now includes Nova Cygni 1992 as an OSSE source. Please see the
updated observing schedule at the bottom for details of periods 22-25.
The maneuver took place from 1549Z-1631Z, and covered an angle of 111
degrees. The observation of Nova Cyg by OSSE is to look for the nuclear
lines from short-lived isotopes created in novae, in particular 7Be which
has a half-life of 53 days, with a line at 478 keV. The changes in period
24 are to permit correlative observations of the Galactic Center with a
planned balloon flight from Australia, and with SIGMA.
Note that the attitude for period 22 (Mar 5 - Mar 19) allows EGRET and
COMPTEL to observe the source QSO 0836+710 mentioned below in the EGRET
IAU Circular at 24 degrees off-axis. Correlative observations could be
possible.
As of February 27, Compton GRO was in an orbit with an apogee of 420.0
kilometers, perigee of 410.5 kilometers, period of 92.9 minutes, and
inclination of 28.5 degrees.
Contingency Planning: The exercise to assess impacts of increasing
real-time support for Compton GRO is near completion.
The Peer Review for Phase 2 Compton Observatory Guest Investigations was
held last week, Feb 24-26. We are now working on developing an
observing plan for Phase 2.
BATSE
-----
As of March 3rd, BATSE has detected 254 cosmic gamma-ray bursts
out of a total of 1356 on-board triggers in 317 days of operation.
There have been 453 triggers due to solar flares with emission
above 60 keV.
During Viewing period 1-22, BATSE folded on board pulsar data will
be collected for the Crab Pulsar, PSR 0656+14, PSR 1509-58, and SMC X-1.
The daily number of BATSE data packets with uncorrected errors
continues to grow.
COMPTEL
-------
Routine operations continue with COMPTEL. A team meeting is currently in
progress at the Laboratory for Space Research in Leiden, The Netherlands. The
status of flight data reduction is under review, as are priorities for
continued processing and analysis activities. The latest scientific results
from the instrument are also being discussed in anticipation of COMPTEL team
presentations at the upcoming conference on Recent Advances in High Energy
Astronomy in Toulouse, France.
EGRET
-----
EGRET operations remain normal. The error rate is continuing
to increase slowly, but at the moment the software that was
installed is handling it. Data reduction is proceeding smoothly.
EGRET scientists are preparing four papers for the meeting on Recent
Advances in High Energfy Astronomy to be held in Toulouse, March 17-20,
1992. One of the papers will be an overview, and the others will be
on 3C 273, Geminga, and the June 11, 1991 solar flare. There will also
be an IAU telegram released shortly on some EGRET results not reported
previously.
The EGRET Team has put out the following IAU Circular (extracted):
Issued by CBAT: Fri, 28 Feb 92 15:22:05 EST Circular No. 5460
Central Bureau for Astronomical Telegrams
QSO 0836+710
The Compton Observatory EGRET Team (C. E. Fichtel, D. L. Bertsch,
R. C. Hartman, S. D. Hunter, P. W. Kwok, J. R. Mattox, P. Sreekumar,
and D. J. Thompson, Goddard Space Flight Center, NASA; D. A. Kniffen,
Hampden-Sydney College; Y. C. Lin, P. F. Michelson, and P. L. Nolan,
Stanford University; E. Schneid, Grumman Aerospace Corporation; and
G. Kanbach, H. A. Mayer-Hasselwander, C. von Montigny, K. Pinkau, H.
Rothermel, and M. Sommer, Max-Planck-Institut fur Extraterrestrische
Physik) reports the tentative identification of a recently detected
source in the gamma-ray energy range above 100 MeV with the quasar
0836+710. The observations were made between Jan. 10 and 23. On
IAUC 5453, Schramm et al. reported an optical flare of 0836+710 in
the same time frame. EGRET will have some additional exposure to
this region of the sky between Mar. 5 and 19.
OSSE
----
OSSE continues to operate well. For viewing period 22, which starts on March 5,
OSSE will be observing the active galaxy MRK 279 as its z-axis target, and
will be observing the recent nova N Cygni 1992 as its priority target.
OSSE continues to work with the FOT in correcting tape recorder errors. It is
hoped that the latest type of error seen on tape recorder B, which causes a
logical inversion of the binary data, will be largely or at least partly
correctable in a similar manner to the bit-slip corrections. The OSSE mission
operations team is working with the GRO Flight Operations Team in dealing with
these new errors.
Since February 20, OSSE slewing to the Sun in response to BATSE solar flare
triggers has been disabled.
GAMMA RAY OBSERVATORY PHASE 1 OBSERVING PLAN as of 3/5/92
Run Start Date Stop Date GRO Z Axis GRO X Axis OSSE Primary Target OSSE Secondary Target
__ ___________ ___________ _____________ _____________ ___________________________ ___________________________
1 16-MAY-1991 30-MAY-1991 88.08 17.14 339.12 46.49 CRAB PULSAR 83.52 22.02 PSR 1957+20 299.84 20.81
2 30-MAY-1991 8-JUN-1991 301.38 36.58 60.30 33.09 CYG X-1 299.59 35.21 NGC 1275 49.96 41.51
2.1 8-JUN-1991 15-JUN-1991 87.83 12.47 338.68 56.03 SUN ~87.83 ~12.26 CYG X-1 299.59 35.21
3 15-JUN-1991 28-JUN-1991 191.55 2.61 101.50 1.04 SN 1991T 188.54 2.66 QSO 0736+016 114.82 1.62
4 28-JUN-1991 12-JUL-1991 179.83 41.52 57.37 31.22 NGC 4151 182.63 39.41 3C 111 64.59 38.02
5 12-JUL-1991 26-JUL-1991 270.39 -30.96 196.56 24.91 G CENTER 0+0 266.40 -28.94
6 26-JUL-1991 8-AUG-1991 91.28 -67.96 153.96 10.52 SN 1987A 83.86 -69.27 MRK 421 166.11 38.21
7.1 8-AUG-1991 15-AUG-1991 310.05 28.06 143.74 61.25 CYG X-3 307.66 40.78 M82 147.90 69.92
7.2 15-AUG-1991 22-AUG-1991 291.98 -13.27 208.11 24.38 G PLANE 25 279.22 -7.05
8 22-AUG-1991 5-SEP-1991 124.96 -46.35 198.99 14.71 VELA PULSAR 128.92 -45.18 SN 1991T 188.54 2.66
9.1 5-SEP-1991 12-SEP-1991 8.34 -32.31 244.20 -41.58 GX 339-4 255.71 -48.79 NGC 253 11.89 -25.29
9.2 12-SEP-1991 19-SEP-1991 251.28 36.89 142.05 23.69 HER X-1 254.46 35.34 MRK 421 166.11 38.21
10 19-SEP-1991 3-OCT-1991 30.91 -60.66 190.28 -27.75 NOVA MUS 171.61 -68.68 3C 279 194.05 -5.79
11 3-OCT-1991 17-OCT-1991 189.02 1.06 278.41 -29.71 3C 273 187.28 2.05 G CENTER 0+0 266.40 -28.94
12 17-OCT-1991 31-OCT-1991 202.28 -40.09 221.48 48.29 CEN A 201.38 -43.01 3C 390.3 280.56 79.76
13.1 31-OCT-1991 7-NOV-1991 291.98 -13.27 208.11 24.37 G PLANE 25 279.22 -7.05 NGC 5548 214.50 25.13
13.2 7-NOV-1991 14-NOV-1991 8.34 -32.31 244.20 -41.58 GX 339-4 255.71 -48.79 ESO 141-55 290.31 -58.67
14 14-NOV-1991 28-NOV-1991 156.83 -58.51 274.30 -15.77 ETA CAR 161.95 -59.98 G CENTER 0+0 266.40 -28.94
15 28-NOV-1991 12-DEC-1991 52.00 40.24 293.35 29.54 NGC 1275 49.96 41.51 CYG X-1 299.59 35.21
16 12-DEC-1991 27-DEC-1991 248.36 -17.20 351.62 -36.55 G CENTER 0+0 266.40 -28.94
17 27-DEC-1991 10-JAN-1992 83.47 -72.26 266.22 -17.72 SN 1987A 83.86 -69.27 G CENTER 0+0 266.40 -28.94
18 10-JAN-1992 23-JAN-1992 154.60 72.04 292.51 13.52 M 82 148.96 69.67 PSR 1929+10 293.05 10.99
19 23-JAN-1992 6-FEB-1992 331.40 -1.93 242.82 36.31 G PLANE 58.1 294.98 22.28 HER X-1 254.46 35.34
20 6-FEB-1992 20-FEB-1992 285.28 6.37 12.01 -27.04 SS 433 287.95 4.99
21 20-FEB-1992 5-MAR-1992 39.09 -1.24 308.13 -37.65 NGC 1068 40.67 -0.01 G CENTER 0+0 266.40 -28.94
22 5-MAR-1992 19-MAR-1992 216.00 70.74 -30.57 7.91 NOVA CYG 92 307.63 52.62 MRK 279 208.24 69.31
23 19-MAR-1992 2-APR-1992 227.43 -54.62 11.72 -29.96 CIR X-1 230.23 -57.18
24.0 2-APR-1992 9-APR-92 223.34 11.03 -57.49 -43.94 GAL CTR 266.40 -28.94
24.5 9-APR-92 16-APR-1992 223.34 11.03 -55.45 -38.07 G PLANE 5+0 268.50 -24.63
25 16-APR-1992 30-APR-1992 1.58 20.20 73.88 -39.57 MRK 335 1.59 20.21 VELA PULSAR 128.42 -45.18
26 30-APR-1992 14-MAY-1992 84.37 46.61 353.16 1.14 MCG +8-11-11 88.73 46.44 III ZW 2 2.63 10.97
27 14-MAY-1992 28-MAY-1992 68.97 -25.09 53.03 64.04 3C 390.3 280.56 79.76 SN 1987A 83.86 -69.27
28 28-MAY-1992 11-JUN-1992 345.76 57.48 100.24 14.79 CAS A 350.87 58.81 GEMINGA 98.48 17.77
29 11-JUN-1992 25-JUN-1992 149.50 -14.74 61.41 7.22 NGC 2992 146.43 -14.33 3C 120 68.29 5.35
30 25-JUN-1992 9-JUL-1992 287.11 -61.21 144.32 -23.64 ESO 141-55 290.31 -58.67 MCG -5-23-16 146.92 -30.96
31 9-JUL-1992 23-JUL-1992 110.40 -10.22 197.74 14.42 M 87 187.71 12.39
32 23-JUL-1992 6-AUG-1992 330.73 -33.09 121.57 -53.26 PKS 2155-304 329.72 -30.22 SMC X-1 19.15 -73.44
33 6-AUG-1992 20-AUG-1992 142.06 30.02 186.76 -50.89 MCG +5-23-16 143.56 27.33 NGC 3783 174.76 -37.74
Posted by:
Tom McGlynn
Compton Observatory Science Support Center
[email protected]
Article: 20984
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.astro
Subject: Compton Observatory Science Report #56
Date: 13 Mar 92 15:35:31 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #56
Thursday, March 12, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
Normal science operations continues using the B Tape Recorder. However, the
error rates of the new type on the B Recorder have become considerably worse
during the past week. Intensive studies of the tape recorder performance,
and of the possibility for expanded real-time operations are underway. A
report has been issued on the feasibility of real-time operations, showing
that Compton HGA gimbal angle limitations permit real time telemetry
coverage for approximately 63-70% of the orbit, depending on spacecraft
attitude, with a very limited attitude range allowing even higher coverage
than this. Other limitations may also come into play.
As of March 5, Compton GRO was in an orbit with an apogee of 418.4
kilometers, perigee of 408.3 kilometers, period of 92.8 minutes, and
inclination of 28.5 degrees. For comparison, as of February 27, Compton
GRO was in an orbit with an apogee of 420.0 kilometers, perigee of 410.5
kilometers, period of 92.9 minutes, and inclination of 28.5 degrees.
A meeting was held March 11, to decide on a date for the first reboost
of the Compton Observatory. A committee chaired by Neil Gehrels selected
the week of September 21, 1992. This is somewhat earlier than previous
estimates, due to the faster than expected decay of the Compton orbit
recently. An attempt will be made to hold to this date, to permit other
project elements to use this date in their planning.
Announcement of the 1992 Compton GRO Postdoctoral Fellowship Awards
The National Aeronautics and Space Administration is proud to announce
the recipients of the 1992 Compton Gamma Ray Observatory Postdoctoral
Fellowships. This program gives young scientists the opportunity to
pursue a research topic of their own choosing in high-energy
astrophysics. The awardees were selected after a review by a panel of
scientists drawn from the astronomical community. The committee selected
the fellows on the basis of the overall scientific merit of the research
program proposed, its likelihood of success, relevance to NASA space
astrophysics and the Compton mission, and the institutional support for
the fellows. The competition was extremely keen with many worthy
applicants. The winning applicants, their research topic, and the
institution at which they will be working are listed below. NASA
congratulates these fellows and anticipates that their insights will
play a major role in the scientific results of the Compton Observatory
mission and other areas of high-energy astrophysics.
Fellow Institution Topic
Haimin Wang California Institute Correlative Studies of Solar
of Technology Flares
Seth Digel Harvard/Smithsonian Gamma Rays from Molecular Clouds
Center for Astrophysics in the Outer Galaxy
Paolo Coppi University of Chicago High Energy Emission from
Compact Objects
Marco Fatuzzo University of Michigan Gamma Ray Bursts
Marc Herant University of Hydrodynamics of Supernovae and
California, Santa Cruz Implications for Gamma Ray Astronomy
BATSE
-----
As of March 9th, BATSE has detected 263 cosmic gamma-ray bursts
out of a total of 1356 on-board triggers in 323 days of operation.
There have been 453 triggers due to solar flares with emission
above 60 keV.
The following has been submitted as an IAU Circular:
GALACTIC CENTER
B. A. Harmon, W. S. Paciesas, B. Rubin, M. H. Finger, G. J.
Fishman, R. B. Wilson, and C. A. Meegan, NASA/Marshall Space
Flight Center, report for the Compton Observatory BATSE Experiment Team:
"Increased hard x-ray emission from the galactic center
region consistent with the position of 1E 1740.7-2942 has been
observed by Earth occultation beginning Feb. 28th and peaking
around March 3rd. The average fluxes between March 2-5 in the
20-50 keV and 50-320 keV energy bands are approximately 280 +- 40
mCrab and 150 +- 30 mCrab and appear to be consistent with the
high state of this source. The spectrum above 50 keV is well fit
by a single power law with index -2.3+-0.2. The flux below 50 keV
may have a contribution from nearby softer x-ray sources."
Papers on BATSE results will be presented at the International
Symposium on Recent Advances in High Energy Astronomy in Toulouse
by Drs. Briggs, Fishman, Kouveliotou, Pasiesas and Schaefer.
Due to the problems caused by tape recorder errors BATSE routine
data processing is two days behind schedule. Software is now
being tested to fix bit flip errors in addition to the bit drop
errors already being corrected. The present error correction code
left 10% of the March 9th data in error. Because BATSE operations
software is unable to cope with this error density, further data
processing must wait for completion of the new error correction code.
COMPTEL
-------
Over the last 24 hours COMPTEL was operated in a test configuration at
the lowest possible energy thresholds, in order to assess the feasibility of
conducting scientific observations in the region of the 511-keV positron
annihilation line (just below the current nominal energy threshold of the
instrument at 700-800 keV). These trial observations are currently under
evaluation.
The COMPTEL operations team continues to monitor the performance of two
(of 14) of the lower detector modules of the instrument. The behavior of one of
these appears to have stablilized, while the other continues to show some
indication of temperature-dependent anomalies. The COMPTEL operations group has
formally requested the Flight Operations Team at Goddard to investigate means
of lowering the temperature within the COMPTEL detector assembly to confirm
this effect. In response to increasing spacecraft tape recorder error rates
both the COMPTEL operations group (at UNH) and the data processing group (at
MPE) have begun to implement error-correction software to minimize the impact
of these errors on routine operations and the scientific data analysis.
The COMPTEL team will be well represented at the meeting in Toulouse,
France next week on Recent Advances in High Energy Astronomy. A total of one
invited, seven contributed, and two poster papers will be presented by the
collaboration. These contributions will cover the main scientific results
obtained to date by the COMPTEL team. Among the topics to be discussed: a first
source map at MeV energies along a portion of the Galactic plane; observations
of the Crab nebula and pulsar; observations of the Vela pulsar; observations of
the quasars 3C273 and 3C279; detection of the 1.8 MeV line from 26-Aluminum
toward the central region of the Galaxy; upper limits to gamma-ray line fluxes
from the extragalactic supernova SN1991T; localization of 8 cosmic gamma-ray
bursts to an accuracy of approximately one degree; measurement of gamma-ray
burst spectra and time profiles; observations of gamma-ray and neutron emission
from solar flares.
EGRET
-----
Although EGRET instrument operations remain normal, primarty
data processing has been suspended because of the large increase in
bit errors of a different type not corrected by the current software.
Gamma ray event data reduction is continuing since this work became
about two weeks behind while software to handle the last type of
bit errors was being written and tested. We expect the new software
that has to be written to handle this new problem to be ready by
this time next week.
The absolute time problem still exists; however, the committee,
chaired by Dave Bertsth, is making progress.
The following IAU Circular has been issued by the EGRET Team (extracted):
Issued by CBAT: Tue, 10 Mar 92 15:40:12 EST Circular No. 5470
Central Bureau for Astronomical Telegrams
MARKARIAN 421, PKS 0537-441, QSO 0716+714
The Compton Observatory EGRET Team (P. F. Michelson, Y. C. Lin,
and P. L. Nolan, Stanford University; D. L. Bertsch, C. E. Fichtel,
R. C. Hartman, S. D. Hunter, P. W. Kwok, J. R. Mattox, P. Sreekumar,
and D. J. Thompson, Goddard Space Flight Center, NASA; D. A. Kniffen,
Hampden-Sydney College; G. Kanbach, H. A. Mayer-Hasselwander, C. von
Montigny, K. Pinkau, H. Rothermel, and M. Sommer, Max-Planck-Institut
fur Extraterrestrische Physik; and E. Schneid, Grumman Aerospace
Corporation) reports the tentative identifications of three BL Lac
objects as high-energy gamma-ray sources: Mrk 421, observed 1991
June 27-July 11; PKS 0537-441, observed 1991 July 26-Aug. 8; and QSO
0716+714, observed 1992 Jan. 10-23. All three sources have flux
values between 1 and 3 x 10E-7 photons cmE-2 sE-1 above 100 MeV. An
additional observation of PKS 0537-441 is planned for the period May
14-28, and an additional exposure to Mrk 421 is scheduled for Aug.
6-20.
1992 March 10 Daniel W. E. Green
OSSE
----
OSSE continues to operate well.
Since March 7, OSSE has been receiving corrections for both bit slip and
bit inversion tape recorder data errors. The OSSE mission operations team
is still working on implementing the corrections for bit inversion errors,
but should have it implemented soon.
Since February 20, OSSE slewing to the Sun in response to BATSE solar flare
triggers has been disabled.
Some recent OSSE results will be presented at the "Recent Results in High
Energy Astrophysics" colloquium, to be held in Toulouse between 17 and 20
March. OSSE team members Neil Johnson, Bill Purcell, Steve Matz, Mark
Leising and Jim Kurfess will be attending the meeting.
Posted by:
Tom McGlynn
Compton Observatory Science Support Center
[email protected]
|
| 636.49 | New Operations for Compton GRO | PRAGMA::GRIFFIN | Dave Griffin | Fri Mar 20 1992 00:35 | 71 |
| Paula Cleggett-Haleim
Headquarters, Washington, D.C. March 18, 1992
RELEASE: 92-39
Mission managers for NASA's Compton Gamma Ray Observatory are
implementing a new operating procedure, because of a problem in the
playback of recorded data. Science observations are continuing without
significant loss of data.
Scientific and spacecraft data will now be transmitted directly to the
Tracking and Data Relay Satellite System (TDRSS) and then to a ground
control center, without using tape recorders. Fortunately, the
capability of TDRSS, using two of its spacecraft, will enable nearly
full coverage of each Compton orbit. This procedure will be used while
an investigation continues into the cause of the problem.
Normally, the four science instruments onboard the observatory collect
data, which are recorded onto one of two tape recorders (designated "A"
and "B"). When a specified amount of data have been collected,
typically about 3-hours worth, the recorded data are played back at
high speed and transmitted to a ground control center using the TDRSS.
The cycle of data collection, recording and transmission, with high
speed playback, is then repeated.
Since early in the mission, minor errors in the data recording and
playback have been detected. As long as the rate remained low,
however, the errors could be removed on the ground using computer
processing.
The errors were first detected in tape recorder A. Mission managers
then decided to switch to tape recorder B, which was experiencing a
lower rate of error. The error rate in B, however, increased in a
short period of time and has reached the point where computer
processing is slow and laborious. Therefore, managers decided to
switch to the new operations mode. This new mode directly relays data
to TDRSS without using recorders.
Compton cannot be in constant communication with TDRSS, because of
"viewing angles." Some data, therefore, will be lost. If the error
rate in the recording/playback process does not significantly worsen,
it may be possible to record and store data during that portion of the
orbit when the Observatory is not in contact with TDRSS. Managers
could then recover data that would otherwise be lost. It is
anticipated that, when fully implemented, a data capture rate of 80
percent of the optimal level will be achieved.
Although the new operating procedure will result in some inefficiency,
the science goals of the mission still can be achieved through
increased observing times. If the recorders are not used at all, the
primary goal of the mission, to conduct an all-sky survey at gamma-ray
wavelengths, will now be completed in late 1992, instead of this
summer, as originally anticipated.
The new procedures should have no effect on the length of the mission,
which is designed for a minimum of 2 years. If the present problem can
be identified and a corrective action implemented, the observatory may
be restored to nominal operations.
The specific cause of the errors is not known, but an investigative
team has been formed at NASA's Goddard Space Flight Center (GSFC),
Greenbelt, Md. The investigation will exam the tape recorders as well
as on-board electronics, which prepares data for recording and playback
in preparation for transmission to the ground.
Compton Gamma Ray Observatory, the second of NASA's Great
Observatories, was launched April 5, 1991, by the Space Shuttle
Atlantis to study high-energy radiation from space. The spacecraft
was developed and is managed and operated by GSFC for NASA's Office of
Space Science and Applications, Washington, D.C.
|
| 636.50 | Updates - March 26 and April 2 | VERGA::KLAES | All the Universe, or nothing! | Wed Apr 08 1992 18:53 | 266 |
| Article: 687
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.space.news
Subject: Compton Observatory Science Report #58
Date: 3 Apr 92 14:51:20 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #58
Thursday, March 26, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
The Compton spacecraft is now operating with real-time telemetry
whenever possible. The percentage of the time when real-time
communication can be achieved has been at or slightly below 50%
these first weeks, and efforts to improve on this are in progress.
Tape recorder data is being used to fill in gaps where possible, but
the very high error rates make the taped data difficult to use.
As of March 19, Compton GRO was in an orbit with an apogee of 415.2
kilometers, perigee of 406.3 kilometers, period of 92.8 minutes, and
inclination of 28.5 degrees. For comparison, as of March 12, Compton
GRO was in an orbit with an apogee of 417.0 kilometers, perigee of 407.3
kilometers, period of 92.8 minutes, and inclination of 28.5 degrees.
The Proceedings of The Compton Observatory Science Workshop, held in
Annapolis on September 23-25, 1991, have now come out as a NASA
Conference Publication (CP-3137). Attendees and some other Project-related
scientists will very soon receive copies in the mail. Copies may be now be
requested from the Compton GRO Science Support Center. They are free.
The fourth issue of the Compton Observatory Newsletter has now been
issued and distributed. In it, among other things, is an explanation
of how to access the Compton GRO SSC on-line news, computation,
bibliography and other assistance packages for users. Copies are
available from the SSC.
The Compton GRO Users Committee met at Garching, Germany this Monday and
Tuesday. Discussions were held on the observing plans for the rest of
Phase 1 and for Phase 2. More news on these topics should be available
next week.
BATSE
-----
As of March 14rd, BATSE has detected 264 cosmic gamma-ray bursts
out of a total of 1374 on-board triggers in 328 days of operation.
There have been 455 triggers due to solar flares with emission above 60 keV.
BATSE data processing is lagging three days behind Pacor deliveries
which are presently seven days behind schedule. Error correction
software is now running smoothly, however the large numbers of errors
remaining in the data are still causing problems. More software changes
to limit the impact of these errors are being made.
COMPTEL
-------
No report this week.
EGRET
-----
Due to the problems with the tape recorded data, EGRET has not been
able to process very much data since early this month. The instrument
appears to be functioning well, based on the available data.
Progress is being made on the absolute time problem by several people,
including Tome Cline, Carl Fichtel and Dave Bertsch, who is chairman of
the ad hoc committee to address this problem.
Recent scientific items (courtesy Bertsch, Fichtel, Hartman,
Hunter, Mattox, Kwok, Sreekumar and Thompson). The following EGRET
papers were presented at the International Conference on "Recent Advances
in High Energy Astronomy" held at Toulouse, France on March 17-20, 1992.
"Overview of the First Results from EGRET" (invited), Carl Fichtel et al.
"High Energy Emission from a Solar Flare of June 11, 1991", Gottfried
Kanbach et al.
"EGRET Observations of the Source 2C 195+04 Geminga", Hans Mayer-
Hasselwander et al.
"EGRET Observations of 3C 273", Corinna Von Montigny et al.
OSSE
----
OSSE continues to operate safely. The recent change in GRO operations to
receive about 50% of telemetry through TDRS real time contacts and the rest
from tape recorder playback has improved OSSE data quality. Delivery of
production telemetry data for OSSE was resumed on March 25 after several days
interruption, and the lag in production data delivery should be recovered in a
few days. The production data received since the change in GRO operations has
about 40% of the tape playback packets deleted and most of the remaining tape
playback packets corrupted.
The FOT repair files that are applied to OSSE telemetry have been seen to
produce incorrect data, indicating that the algorithms used by the FOT to
discover and correct telemetry errors, when applied to the very high error
rates produced by tape recorder B, can result in occasional spurious
corrections. The OSSE team is prepared to support any effort to increase
viable GRO telemetry back to near 100%, including resumption of the use of
tape recorder A.
Since February 20, OSSE slewing to the Sun in response to BATSE solar flare
triggers has been disabled.
Posted by: Tom McGlynn
Compton Observatory Science Support Center
[email protected]
Article: 670
From: [email protected] (Thomas McGlynn)
Newsgroups: sci.space.news
Subject: Compton Observatory Science Report #59
Date: 3 Apr 92 14:53:58 GMT
Sender: [email protected] (Usenet)
Organization: Goddard Space Flight Center
Compton Observatory Science Report #59
Thursday, April 2, 1992
Eric Chipman, Compton Observatory Science Support Center
Questions or comments can be sent to the Compton SSC. Phone 301/286-7764,
e-mail SPAN GROSSC::CHIPMAN, Internet [email protected].
The Compton spacecraft continues operating with real-time telemetry
whenever possible. Tape recorder data is being used to fill in gaps where
possible, but the very high error rates make the taped data difficult to use.
A maneuver was done this morning to point to the attitude for period 24, as
described by OSSE below. The maneuver took place from 1249 to 1310Z, and
covered an angle of 39 degrees.
The realtime science data acquisition mode implemented on March 18th has
proceeded in such a way that GRO is averaging about 45% realtime coverage of
a total realtime maximum visibility of approximately 54%. In addition tape
recorder B is used during non-realtime periods and error corrected by the
the FOT on the ground.
Special Tiger Team observatory tape recorder tests are planned. Procedures
are prepared and testing ready to begin as early as 27 March, pending
availability of TDRS passes. Available passes will be the primary constraint
until the Shuttle returns from orbit, on 1 April.
Odetics has provided a test plan for on-ground testing of a tape recorder
similar to GROs in an effort to reveal the cause of the problem.
The current plan is that Phase 1, the all-sky survey, will be extended
from August 20 until November 15 to make up for the loss in data coverage due
to the tape recorder problems.
BATSE
-----
As of 3/16/92, BATSE has detected 271 cosmic gamma-ray bursts
out of a total of 1400 on-board triggers in 330 days of operation.
There have been 456 triggers due to solar flares with emission
above 60 keV.
During Viewing period 1-24, BATSE folded on board pulsar data will
be collected for the Crab Pulsar, PSR 0656+14, PSR 1509-58,
PSR 1706-44, PSR 1737-30, and Her X-1.
The BATSE Operations Team is slowly but surely working its way
through the worst data from two weeks ago. We are now up to date
on PACOR data deliveries, and expect to quickly catch up when
we begin processing the real-time only data. Modifications are
being made to ground software to handle new problems resulting
from the reduced amount of data, and to make better use of
redundancy inherent in the BATSE burst data. Modifications to
flight software are in the planning and initial design stage.
COMPTEL
-------
The COMPTEL collaboration is preparing a number of papers on team presentations
for inclusion in the proceedings of the recent meeting in Toulouse, France on
high-energy astronomy, to appear in a special volume of the journal Astronomy
and Astrophysics.
Since the beginning of real-time data acquisition, the COMPTEL operations group
has noted that approximately 40 to 50% of the maximum possible recovery of
COMPTEL data from the spacecraft has been achieved. The receipt of error-free
real-time data has greatly eased earlier difficulties of the COMPTEL operations
group in monitoring instrument health and performance. Both the COMPTEL
operations and data processing groups continue to install and implement
error-correction software at UNH and MPE in order to salvage as much
information as possible from corrupted tape-recorded data from the spacecraft.
Given the backlog in BATSE burst processing at present, the quick-look analysis
of COMPTEL bursts has been halted for the time being, since it is impossible to
identify from burst triggers alone those few hard bursts that are likely to
fall within COMPTEL's field of view.
Members of the COMPTEL team at MPE supported the meeting of the Compton
Observatory Users' Committee held last week in Garching, Germany.
EGRET
-----
EGRET operations staff are about to attempt to analyze the tapes received
after March 5, but they have concluded that they will have to develop some
new software to analyze the data for the period after March 11 or 12 due to
the large error rates in this data. No data has yet been received for
analysis after March 18.
Because there can be strong overlap between the periods of target visibility,
periods of South Atlantic Anomaly passage, and periods of TDRS-East visibility,
especially for targets in the southern hemisphere, the percentage of usable
data that was obtained in real time in periods 22 and 23 was not as large as
hoped. It appears that the total sensitivity for periods 22 and 23 will be
well below the desired level and that substantially more viewing time will be
needed for both these portions of the sky. Initial expectations for period 24
are also not very good.
From the available data there is no indication that the EGRET instrument is
not continuing to function normally; however, full data from controlled long
instrument runs during unocculted periods outside of the South Atlantic
Anomaly are necessary to determine the detailed quality of the instrument
performance. We cannot currently obtain such data.
The following IAU Circular (extract included here) has appeared this week,
announcing the discovery by EGRET of the third high-energy gamma-ray pulsar
(after the Crab and Vela pulsars):
Issued by CBAT: Tue, 31 Mar 92 13:55:50 EST Circular No. 5485
PSR 1706-44
The Compton Observatory EGRET Pulsar Team (D. A. Kniffen,
Hampden-Sydney College; D. L. Bertsch, C. E. Fichtel, R. C. Hartman,
S. D. Hunter, P. W. Kwok, J. R. Mattox, H. I. Nel, P. Sreekumar and
D. J. Thompson, NASA Goddard Space Flight Center; J. M. Fierro, Y. C.
Lin, P. F. Michelson and P. L. Nolan, Stanford University; E. Schneid,
Grumman Aerospace Corporation; G. Kanbach, H. A. Mayer-Hasselwander,
C. von Montigny, K. Pinkau, H. Rothermel and M. Sommer, Max-Planck-
Institut fur Extraterrestrische Physik; S. Johnston and R. Manchester,
CSIRO; V. Kaspi and J. Taylor, Princeton University; A. G. Lyne,
University of Manchester, Jodrell Bank) reports a significant
detection of pulsed gamma radiation above 100 MeV from PSR 1706-44, at
the radio period of 102 ms, in an observation made during 1991 July
12-27. The gamma-ray source was identified by COS-B as 2CG 342-02.
Unlike the Crab and Vela pulsars, the high-energy gamma radiation from
PSR 1706-44 exhibits a single broad pulse. EGRET is now viewing this
pulsar again and will do so until Apr. 6.
OSSE
----
OSSE continues to operate safely. OSSE data is now being received only from
real time contacts with GRO through TDRS. No tape recorder data is currently
being delivered because of its high error rate. Therefore about 50% of OSSE
data is being received.
For viewing period 24, which starts on 2 April, the primary OSSE target will
be the galactic center, and the secondary OSSE target will be a combined
observation of NGC 4151 and NGC 7582. It is expected that this viewing period
will be a 3 week viewing period, to make up for the reduced amount of data from
GRO. The Phase 1 sky survey carried out by GRO is likely to be extended by
3 months to make up for the reduced data rate. OSSE will soon be scheduling
target observation times around TDRS contact times, either obtained from TDRS
contact schedules if available or predicted from GRO ephemeris data.
Since February 20, OSSE slewing to the Sun in response to BATSE solar flare
triggers has been disabled.
Posted by: Tom McGlynn
Compton Observatory Science Support Center
[email protected]
|
| 636.51 | BL Lacertae galaxies emitting gamma rays | VERGA::KLAES | All the Universe, or nothing! | Wed Apr 08 1992 19:21 | 61 |
| Article: 714
From: [email protected] (Peter E. Yee)
Newsgroups: sci.space.news
Subject: Compton Observatory detects active galaxies (Forwarded)
Date: 8 Apr 92 18:09:45 GMT
Sender: [email protected]
Organization: NASA Ames Research Center, Moffett Field, CA
Michael Braukus
Headquarters, Washington, D.C. April 8, 1992
(Phone: 202/453-1549 )
Randee Exler
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-8955 )
RELEASE: 92-47
COMPTON OBSERVATORY DETECTS ACTIVE GALAXIES
NASA's Compton Gamma Ray Observatory has made the first detection
of high-energy gamma rays from a class of active galaxies similar to
quasars. The observations, made by the Energetic Gamma Ray Experiment
Telescope (EGRET), suggest that high-energy gamma radiation provides a
substantial contribution to the objects' overall luminosity.
These active galaxies are called BL Lacertae objects, a type
of "quasar-like" object that emits vast but varying amounts of energy.
The candidate objects are in the constellations Ursa Major, Pictor and
Camelopardalis. They are designated as MK 421, 0537-441 and 0716+714,
respectively.
These new gamma-ray results support the hypothesis that BL
Lacertae objects, like quasars, may be powered by supermassive black
holes. The detection of these high energy gamma rays also provides
another piece of evidence suggesting their similarity to quasars and
adds important new insight into understanding the nature of BL Lacertae
objects.
The EGRET science team previously reported detection of high
energy gamma rays from six quasars. The most intense, called 3C 279,
registered a total high-energy gamma ray emission more than 10- to
100-million times that of the Milky Way galaxy.
EGRET, one of four instruments aboard the Compton Observatory,
was assembled in-house by the Goddard Space Flight Center, Greenbelt,
Md. The U.S. Principal Investigator for EGRET is Dr. Carl Fichtel of
NASA's Goddard Space Flight Center.
Co-principal investigators for EGRET are Dr. Carl Fichtel, of
Goddard, and Dr. Klaus Pinkau, Max Planck Institute for
Extraterrestrial Physics, Garching, Germany. EGRET is the joint effort
by scientists and engineers at Goddard; Stanford University, Calif.;
Max Planck Institute and Grumman Aerospace Corp., Bethpage, N.Y.
The second of NASA's Great Observatories, the Compton Observatory
was launched April 5, 1991, by the Space Shuttle Atlantis to study
high-energy radiation from space. The Compton Observatory is managed
and operated by Goddard for NASA's Office of Space Science and
Applications, Washington, D.C.
|
| 636.52 | Compton GRO Monthly Status 6/30/92 | PRAGMA::GRIFFIN | Dave Griffin | Mon Jul 06 1992 11:54 | 45 |
| COMPTON GAMMA RAY OBSERVATORY
MONTHLY STATUS REPORT
June 30, 1992
NASA's Compton Gamma Ray Observatory spacecraft and its
instruments continue to perform well.
Compton is in normal pointing mode with solar arrays pointed
toward the Sun.
Compton orbits with an apogee of 249 miles (401 km), perigee
244 miles (393 km), period 92.5 minutes, and inclination of 28.5
degrees.
Realtime data acquisition through the Tracking and Data
Relay Satellite System (TDRSS) remains the primary mode for data
recovery from the observatory since March 18, because of onboard
tape recorder problems.
Based on the number of packets of data delivered to the
instrument groups, the daily percentage of full-time coverage
achieved through TDRSS during June averaged 88 percent.
Compton's onboard batteries continue to provide ample power
for the observatory. On June 24, a higher than normal
differential voltage was observed in one of the three batteries
in Modular Power Subsystem (MPS) -1. Differential voltage is the
difference in amount of charge stored in the 22 cells of each
spacecraft battery. The high differential voltage indicates a
reduced electrical storage capacity for that battery. To
compensate for the reduced capacity, the Energetic Gamma Ray
Experiment Telescope (EGRET) instrument, which uses the most
electrical power of the four Compton instruments, was transferred
from MPS-1 to MPS-2 on June 25.
The performance of the batteries continues to be monitored
very closely.
Compton controllers plan to maneuver next to the NGC 2992
target on July 2. The observatory will remain at that attitude
for two weeks.
The Compton Observatory is managed and operated by the
Goddard Space Flight Center for NASA's Office of Space Science
and Applications.
|
| 636.53 | Compton discovers "Gamma Ray Afterglow" on the Sun | PRAGMA::GRIFFIN | Dave Griffin | Wed Jul 15 1992 20:53 | 62 |
| Paula Cleggett-Haleim
Headquarters, Washington, D.C. July 15, 1992
(Phone: 202/453-1547)
Jim Elliott
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-6256)
RELEASE: 92-112
COMPTON DISCOVERS "GAMMA RAY AFTERGLOW" ON THE SUN
Solar scientists are puzzling over an unexpected "gamma ray afterglow"
discovered on the sun by NASA's Compton Gamma Ray Observatory.
The glow, a strong emanation of high-energy gamma rays, persisted
for more than 5 hours after a solar flare explosion on June 11, 1991, Dr.
James M. Ryan, of the University of New Hampshire, reported at a briefing
at NASA Headquarters in Washington, D.C., today.
A similar phenomenon occurred four days later, this time lasting more
than 90 minutes, he said.
One theory is that the glow resulted when protons, boosted to
energies of tens and hundreds of millions of electron volts by magnetic
processes in the explosion, were stored in a series of magnetic loops, Ryan
explained.
They apparently constituted a coronal arcade or so-called "magnetic
slinky" in the sun's outer atmosphere or corona, he said. Protons are
subatomic particles resulting from a nuclear reaction.
If the theory is correct, Ryan said, the protons are stored at the sun
much the same way as protons are stored in the Earth's Van Allen radiation
belts. However, on the sun, he explained, they slowly leak out to produce
the gamma rays seen by the Compton Observatory.
Under those circumstances, scientists can draw an analogy from the
Earth environment and apply it to the sun's environment, Ryan explained.
Thus, if scientists' understanding of how particles behave in the Van Allen
radiation belts can be applied to the sun, that knowledge would improve
their understanding of what's happening on the sun, he continued.
The work was accomplished using the Energetic Gamma Ray
Experiment Telescope and Imaging Compton Telescope instruments on the
observatory by Drs. Gottfried Kanbach and Mark McConnell of the Max
Planck Institute for Extraterrestrial Physics in Garching, Germany, and the
University of New Hampshire, respectively.
The Compton Gamma Ray Observatory is managed by the Goddard
Space Flight Center, Greenbelt, Md., for NASA's Office of Space Science and
Applications, Washington, D.C.
- end -
EDITORS NOTE: To illustrate this story, three photographs are available to
the news media by calling NASA's Broadcast and Imaging Branch on
202/453-8375. The photo numbers are:
Color B&W
92-HC-451 thru -453 92-H-501 thru -503
|
| 636.54 | First image of Sun in neutrons released | PRAGMA::GRIFFIN | Dave Griffin | Wed Jul 15 1992 20:54 | 48 |
| Paula Cleggett-Haleim
Headquarters, Washington, D.C. July 15, 1992
(Phone: 202/453-1547)
RELEASE: 92-113
FIRST IMAGE OF SUN IN NEUTRONS
NASA's Compton Gamma Ray Observatory has taken the first image
of the sun in neutrons. It is the first picture of any celestial
object ever made with neutrons.
Neutrons are heavy subatomic particles without any electrical
charge. Until today, all images of cosmic objects have been obtained
with one or another form of light -- for example, radio, infra-red,
visible, x-ray and recently gamma rays (from Compton). Scientists now
have a picture of the sun in taken in the "light" of neutrons, which is
matter rather than light.
"This represents a technological breakthrough," says Dr. Jim
Ryan, University of New Hampshire, Durham, "being able to capture an
image through the transmission of matter rather than electromagnetic
radiation." Dr. Ryan is co-principal investigator on the COMPTEL
experiment, one of four instruments on the Compton Observatory.
The image was obtained after the large solar flare (an immense
explosion on the sun) of June 15, 1991.
The neutrons, created in nuclear collisions on the sun, were
detected when they penetrated the radiation sensors in the COMPTEL
experiment onboard the Compton Observatory and produced flashes of
light that were recorded by photomultipliers in the experiment. The
image was then constructed in a computer.
Solar flares have dramatic effects on the Earth's atmosphere
and other aspects of the environment. The Compton Observatory was
deployed from the Space Shuttle Atlantis on April 7, 1991. It was
developed by and is managed and operated by Goddard Space Flight
Center, Greenbelt, Md., for NASA's Office of Space Science and
Applications.
-end-
EDITORS NOTE: Two images are available to the news media by calling
NASA's Broadcast and Imaging Branch at 202/453-8375. The photo numbers
are:
Color B&W
92-HC-454 92-H-504
|
| 636.55 | Compton GRO Status - 8/31/92 | PRAGMA::GRIFFIN | Dave Griffin | Wed Sep 02 1992 14:33 | 12 |
| COMPTON GAMMA RAY OBSERVATORY: Compton scientists have discovered
an unusually bright new source of X-rays and gamma-rays in the
constellation Perseus. The source was detected August 8 using
the Burst and Transient Source Experiment (BATSE). Compton was
reoriented August 10 so that all four instruments could study the
new source. The energetic radiation is coming from a location in
the sky where there was no previously-known source of X-rays or
gamma-rays, according to Dr. Gerald Fishman, at Marshall Space
Flight Center, Huntsville, Ala. Fishman is the principal
investigator for the BATSE, the instrument which detected the
source. Compton launched April 5, 1991 aboard the Space Shuttle
Atlantis.
|
| 636.56 | GRO Status - September 1992 | PRAGMA::GRIFFIN | Dave Griffin | Thu Oct 08 1992 22:37 | 12 |
|
COMPTON: Compton scientists continued studying an unusually bright
X-ray nova in the constellation Perseus this month. The spacecraft
was reoriented to get an even closer look at the object, which was
seen continuously for approximately one month before fading in mid-
September. After September 17, the Energetic Gamma Ray Experiment
Telescope (EGRET) and Imaging Compton Telescope (COMPTEL)
instruments resumed the nearly complete all-sky survey. As of
September 22, the Burst and Transient Source Experiment
(BATSE) detected 436 cosmic gamma-ray bursts. Compton launched
April 5, 1991 aboard the Space Shuttle Atlantis.
Contact: Randee Exler (301) 286-7277
|
| 636.57 | Compton Monthly Status - October 1992 | PRAGMA::GRIFFIN | Dave Griffin | Mon Nov 09 1992 17:57 | 10 |
|
Compton is in a normal pointing mode with solar arrays pointed toward
the Sun. The performance of the batteries continues to be monitored very
closely with power configurations adjusted as necessary. The science teams
anticipate finishing the all-sky survey in mid-November. Among the Compton
results presented at a symposium at Washington University, St. Louis, Mo., this
month, was a map presented by the Imaging Compton Telescope (COMPTEL) team of
radioactive aluminum that may have originated from supernovae or novae from the
distant past. Compton launched April 5, 1991 aboard the Space Shuttle
Atlantis.
|
| 636.58 | COMPTON Monthly Status Report 11/30/92 | PRAGMA::GRIFFIN | Dave Griffin | Wed Dec 16 1992 09:38 | 11 |
| Battery performance continues to be monitored very closely, with power
configurations adjusted as necessary. The observatory is functioning normally
with primary systems powered from modular power subsystem 2, which is
performing very well. Modular power subsystem 1 continues to support a reduced
load of mainly heaters. A Tracking and Data Relay Satellite (TDRS) ground
station is under development at Tidbinbilla, Australia, as part of an effort to
increase real-time data collection from Compton via three TDRSs. All science
instruments are performing nominally.
Source:NASA Spacelink Modem:205-895-0028 Internet:192.149.89.61
|
| 636.59 | Nearby Prehistoric Supernova - Compton Confirmation | PONIL::J_BUTLER | E pur, si muove... | Mon Mar 01 1993 10:22 | 127 |
| Article 3152 of sci.space.news:
Newsgroups: sci.space.news
Path: nntpd2.cxo.dec.com!nntpd.lkg.dec.com!news.crl.dec.com!deccrl!caen!zaphod.mps.ohio-state.edu!howland.reston.ans.net!agate!dog.ee.lbl.gov!network.ucsd.edu!ames!dont-send-mail-to-path-lines
From: [email protected] (Peter Yee)
Subject: Supernova may have caused huge void around solar system [Release 93-36] (Forwarded)
Message-ID: <[email protected]>
Apparently-To: [email protected]
Followup-To: sci.space
Originator: [email protected]
Sender: [email protected]
Reply-To: [email protected] (Peter Yee)
Organization: NASA Ames Research Center, Moffett Field, CA
Date: Sat, 27 Feb 1993 04:51:22 GMT
Approved: [email protected]
Lines: 109
Michael Braukus
Headquarters, Washington, D.C. February 25, 1993
(Phone: 202/358-1547)
Michael Finneran
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 310/286-5565)
RELEASE: 93-036
SUPERNOVA MAY HAVE CAUSED HUGE VOID AROUND SOLAR SYSTEM
A supernova that shone in the ancient sky like a second moon
is the probable cause of a huge void known as the "Local Bubble"
that envelopes the solar system and many nearby stars, a NASA
scientist reported in today's issue of the British journal
"Nature."
The bubble is an area about 300 light-years across that,
compared to other parts of space, is relatively empty of gases
except for super-hot hydrogen. The bubble's origin has been the
subject of intense speculation for the last 20 years.
Now, researchers at NASA's Goddard Space Flight Center,
Greenbelt, Md., say evidence suggests it was formed by the
supernova or explosion of a star known as Geminga about 340,000
years ago.
"This is a supernova we didn't know about until last year.
We put this new knowledge together with some other information
about the Local Bubble, and we were able to say we think we know
what happened here," said Dr. Neil Gehrels, of Goddard. Gehrels
wrote the paper with Dr. Wan Chen, of Universities Space Research
Association.
A supernova is an internal explosion that blows away a
star's outer layers, leaving a dense, collapsed, rapidly spinning
core that emits energy in pulses. Stars that have undergone a
supernova are known as pulsars. The Local Bubble would have been
formed by the force of the supernova blasting most of the gases
out of the surrounding interstellar medium, according to the
authors.
"This must have been the brightest supernova ever seen by
Homo sapiens," said Gehrels. "Everybody would have immediately
noticed it. It would have been quite a spectacular and
frightening event, though not one that would have threatened the
planet's existence."
Supernovas always create such bubbles, Gehrels said.
Similar bubbles, including a cluster of several around the Local
Bubble, probably were formed around our solar system millions of
years ago by supernovas just as close as Geminga. But those
would have collapsed and dissipated by now, leaving little or no
trace of their existence, he said.
Astrophysicists have long speculated that the current Local
Bubble was created by a supernova. But for that to have
happened, the star would had to have been relatively nearby.
Until recently, the evidence for that was scant, said Gehrels.
In the last year, however, several discoveries have given
weight to the theory. Scientists at Goddard and Columbia
University in New York City determined that Geminga is a pulsar
and therefore had to have undergone a supernova at some point.
That finding was made using x-ray data from the Roentgen
Satellite and was confirmed by NASA's Compton Gamma Ray
Observatory.
From Geminga's pulsations, scientists calculated that the
star is no more than 340,000 years old and was about 180 light
years away -- close enough to have created the bubble -- when the
supernova occurred. The authors estimate Geminga has since moved
to about 400 light-years away.
Further evidence recently presented by a team of Italian
astronomers helped Gehrels and Chen place Geminga more precisely.
Calculations based on its speed suggested the star was born in a
position to have created the bubble. The Italian team also
reported that the swiftness with which Geminga crosses the sky
indicates it is not far away.
"So we now know the position for this nearby supernova,"
Gehrels said. "It is right near the current middle of the Local
Bubble."
Gehrels said the supernova that created the bubble would
have been a unique experience for anyone on Earth who witnessed
it.
According to Gehrels, observers would have seen the sudden
appearance of a star emitting as much light as the moon, visible
even in daylight. With a full moon in the sky, the nights would
have been twice as bright as usual. Geminga would have lingered
like a beacon for several months before fading. Currently, it
cannot be seen with the naked eye.
At the time of the supernova, intense x-rays and gamma rays
from the explosion likely would have depleted the Earth's ozone
layer by 10 to 20 percent globally, Gehrels said in remarks not
included in the "Nature" paper. The resulting increase in
ultraviolet radiation, he said, would have been small enough not
to disrupt life on Earth but may have been noticed by early
humans.
"Whomever was here back then would have experienced a
sunburn for a year or two," Gehrels said. "One can only wonder
if anybody at that time figured out that Geminga was the cause."
|
| 636.60 | Satellite data shake theories on gamma-ray bursts | PRAGMA::GRIFFIN | Dave Griffin | Tue Apr 27 1993 18:40 | 110 |
| Paula Cleggett-Haleim
Headquarters, Washington, D.C. April 22, 1993
Michael Finneran
Goddard Space Flight Center, Greenbelt, Md.
Jim Sahli
Marshall Space Flight Center, Huntsville, Ala.
RELEASE: 93-72
New findings from a NASA satellite indicate that powerful gamma-ray
bursts, one of the great mysteries of astronomy, may be more energetic than
previously thought and appear to originate far beyond the Milky Way galaxy.
The new data from the Compton Gamma-Ray Observatory raise the
possibility that the bursts of high energy radiation may be caused by unknown
objects or phenomena in the universe, scientists said at a press conference
today at NASA Headquarters, Washington, D.C.
"These results eliminate some theoretical models entirely and produce
severe constraints on other possible theories" about the source of the
gamma-ray bursts, said Dr. Carl E. Fichtel of NASA's Goddard Space Flight
Center, Greenbelt, Md. He is the co-principal investigator for one of the
satellite's instruments, the Energetic Gamma Ray Experiment Telescope (EGRET).
The critical new data include observations of the highest energy
gamma-rays ever recorded in a burst.
A 2-year mapping survey by another satellite instrument, the Burst and
Transient Source Experiment (BATSE), show that the bursts are evenly
distributed in space. BATSE has seen an average of one gamma-ray burst a day
since the observatory was launched on April 5, 1991. As of March 23, 1993, 591
bursts have been recorded.
The pattern of the bursts on the sky has shown them to be distributed
like no other known objects in the Milky Way, indicating that they may
originate outside the galaxy, said Dr. Chryssa Kouveliotou, a BATSE team member
who works for Universities Space Research Association, a contractor at NASA's
Marshall Space Flight Center, Huntsville, Ala.
Super Bowl Burst
An important clue to the puzzle was obtained on Jan. 31, 1993, when
EGRET recorded a gamma-ray burst that was 10 times higher in energy than any
previously observed since the launch of Compton. The burst -- dubbed the "Super
Bowl Burst" because it was seen on Super Bowl Sunday -- was more than 100 times
brighter at its peak than the brightest steady source of gamma rays in the
Milky Way galaxy and more than 1,000 times brighter than any other known
sources outside the Milky Way.
Aside from its extreme brightness, this event is similar in most other
respects to the other bursts recorded by Compton and earlier satellites.
Because bursts this bright are relatively rare and the EGRET experiment views
only a small portion of the sky at a particular time, astronomers were
incredibly lucky to have this event occur when EGRET was pointed in that
general direction. The nature of the burst indicates that many more may be
occurring than scientists detect.
"The EGRET observation of the highest-energy gamma rays suggests they
may be emitted in a small beam, like a spotlight, to escape the source," said
Dr. Brenda Dingus, an EGRET team member who works for Universities Space
Research Association at Goddard. "However, to observe such a small beam, it
must be pointed at us. So there may be many more objects emitting gamma-ray
bursts that we do not see because their beams point elsewhere."
Both the BATSE and EGRET results undercut the two most widely accepted
models that attempted to explain gamma-ray bursts prior to Compton's launch.
One model says the bursts are energy releases from neutron stars and
are confined to the Milky Way galaxy and a region, or "halo," surrounding it.
A neutron star is the small, extremely dense remnant core of a star that has
exploded in a supernova. Since the Earth is in the outer suburbs of the Milky
Way, more bursts should be seen toward the more densely populated center of the
galaxy than elsewhere, according to this model.
"But that hasn't turned out to be the case. Gamma-ray bursts do not
seem to cluster in a preferred region of the sky," said Kouveliotou. "These
bursts are emitted from all directions and vary greatly in intensity and time
structure."
Colliding Black Holes
Another model suggests that gamma-ray bursts emanate from the distant
reaches of the universe, possibly the result of stars exploding or neutron
stars or black holes colliding. Black holes are believed to be stars that have
collapsed to such high density that light cannot escape their resulting
super-gravity. Many of these models predict that the gamma rays are the
thermal energy from the hot, glowing body produced in these explosions or
collisions. But the gamma rays seen by EGRET from the Super Bowl Burst are not
of the thermal type.
"This begs the question -- If these collisions or explosions are not
the source of gamma-ray bursts, what are? We don't know yet," said Marshall's
Dr. Gerald Fishman, the BATSE Principal Investigator. "It is possible that some
new object or phenomenon is producing these bursts."
Fishman said the Compton data will be studied by scientists from around
the world who are seeking to unravel the puzzle of gamma-ray bursts.
"It's difficult to say exactly where this new information will lead,"
said Fishman, "but it's probably safe to assume that we'll have to rewrite the
textbook on gamma-ray bursts."
The Compton Gamma-Ray Observatory is managed by Goddard Space Flight
Center for the Office of Space Science at NASA Headquarters, Washington, D.C.
BATSE was developed by Marshall Space Flight Center. EGRET was developed by
Goddard.
|
| 636.61 | Its SO Simple | MAYDAY::ANDRADE | The sentinel (.)(.) | Wed Apr 28 1993 05:13 | 3 |
| (-; Its obvious to me what is causong those Gamma Ray Bursts
its ... simple ... its amazing ... so ... it must be true ...
its Alien Spacecraft turning on their Anti-Matter Engines :-)
|
| 636.62 | | FASDER::ASCOLARO | Mountain Jam | Wed Apr 28 1993 12:20 | 1 |
| Honestly, that was my first thought also :)
|
| 636.63 | | AUSSIE::GARSON | nouveau pauvre | Mon May 10 1993 05:08 | 37 |
| re .61,.62
Just in case not all readers here also read PHYSICS, you guys might
want to take the following into account when you're working on your
theory. (-:
<<< DECWET::DOCD$:[NOTES$LIBRARY]PHYSICS.NOTE;1 >>>
-< Physics >-
================================================================================
Note 283.25 Physics News Update (328.* for discussion) 25 of 27
CADSYS::COOPER "Topher Cooper" 61 lines 6-MAY-1993 14:11
-< #125 >-
--------------------------------------------------------------------------------
PHYSICS NEWS UPDATE
A digest of physics news items prepared by Phillip F. Schewe, AIP
Public Information
Number 125 April 22, 1993
:
:
ASTROPHYSICAL GAMMA RAY BURSTS COME IN TWO FORMS,
according to Don Lamb of the University of Chicago
who examined 200 of the 600 or so bursts recorded so far by the
Gamma Ray Observatory. In one class (25-33% of the sample)
the bursts are relatively short (less than 10 seconds), faint, rapidly
varying in intensity, have relatively "hard" spectra (much of their
energy is above 300 keV), and are uniformly distributed in space.
For the other class, the bursts are faint and bright, long (between
.3 and 1000 seconds in duration), softer, less variable in intensity,
and not uniform in distribution. Lamb said that he expected his
new classification scheme to help in the effort to determine the
origin of the mysterious bursts, none of which has yet been
correlated with a known object in the sky. (APS meeting.)
:
:
|
| 636.64 | Compton Observatory discovers intense new x-ray pulsar | PRAGMA::GRIFFIN | Dave Griffin | Wed Aug 04 1993 10:21 | 86 |
| Paula Cleggett-Haleim
Headquarters, Washington, D.C. August 3, 1993
Jerry Berg
Marshall Space Flight Center, Huntsville, Ala.
RELEASE: 93-141
Using NASA's Earth-orbiting Compton Gamma-Ray Observatory, scientists have
discovered a powerful pulsar which has become one of the brightest x-ray
sources in the sky during the past 2 weeks.
A pulsar is an unusual celestial object or system that emits pulses of
radiation at regular intervals. The new pulsar emits a pulse of x-rays every
93.5 seconds. That also is the period of rotation for the pulsar. A pulsar's
flashes of energy are emitted much like the sweeping motion of a lighthouse
beam.
Several hundred pulsars emitting radio energy have been found, but only
about 30 have been found that emit x-rays, nearly all of them within the Milky
Way galaxy. The new pulsar is thought to be one of an even smaller class of a
half-dozen objects called transient x-ray pulsars. These undergo enormous
change in brightness on time-scales ranging from hours to years.
The energy outbursts occur when matter, emitted as a "solar wind" from a
high-mass star, falls onto a neutron star in orbit around it. A neutron star,
although it has a diameter of only about 12 miles (20 km), and about the same
mass as Earth's sun, has a much higher gravitational field since it is so
dense.
Continued observations will be required to determine if the newly
discovered object definitely is an object of this type. "When we first saw this
pulsar in our data, it was a tremendous moment," said Dr. Robert B. Wilson of
the Space Science Laboratory at NASA's Marshall Space Flight Center,
Huntsville, Ala.
"For 2 years we had been watching the data and up to now, we had only
observed previously known pulsars. All such observations are useful in trying
to understand these objects, but it's much more exciting when you find
something new," Wilson said.
The new object was first observed in data from a Compton instrument called
the Burst and Transient Source Experiment (BATSE), which can view the entire
sky simultaneously. The source brightened from the initial detection level to
become as bright as any other known x-ray pulsar in five days, remained there
for about 2 weeks and now has started to decrease.
The new pulsar is designated GRO J1008-57 and is in the southern
constellation Carina.
The BATSE pulsar data analysis team which discovered the x-ray pulsar
is led by Wilson. Initial discovery of the pulsed signal from the object was
made by Mark Stollberg, a Ph.D. graduate student at the University of Alabama
in Huntsville, and Dr. Mark H. Finger of the Gamma Ray Observatory Science
Support Center at NASA's Goddard Space Flight Center, Greenbelt, Md.
Astronomers around the world were notified of the new pulsar by a circular
distributed by the Central Bureau for Astronomical Telegrams in Cambridge,
Mass.
A wide-field optical plate of the region containing the source has been
made by an observatory in Australia, under the direction of Dr. Malcolm Coe of
the University of Southhampton, England, to attempt to identify the companion
star. BATSE alone can provide the location of the source to an accuracy of
only about 2 degrees, so it is a difficult task to find which star is the
optical counterpart.
Special maneuvers of the Compton Observatory are being made so that the
other experiments aboard the observatory can view the new pulsar and perhaps,
supplement the BATSE data.
The Compton Observatory has been providing data on x-ray pulsars since it
was launched by the Space Shuttle in April 1991. Compton has observed about 15
of the objects to date.
Most known x-ray pulsars were discovered by instruments on U.S. rockets
that flew in the 1960s, by U.S. and British experiments aboard spacecraft
during the 1970s and by European, Russian and Japanese experiments aboard
spacecraft during the 1980s. GRO J1008-57 is the first discovered by a U.S.
spacecraft in more than 15 years.
Compton is managed by the Goddard Space Flight Center for NASA's Office of
Space Science, Headquarters, Wash., D.C.
|
| 636.65 | The difficult hunt for GRB sources | VERGA::KLAES | Quo vadimus? | Thu Sep 16 1993 19:12 | 86 |
| Article: 43252
From: [email protected] (David M. Palmer)
Newsgroups: sci.astro,sci.space
Subject: Gamma-Ray Bursts (was Re: Urgant)
Date: 16 Sep 1993 08:35:25 GMT
Organization: California Institute of Technology, Pasadena
The discussion on aliens has sequed into a discussion on the origin of
gamma-ray bursts, so I thought I'd update the net on the latest
developments.
Gamma-ray bursts are intense bursts of gamma-rays, over time scales
from milliseconds to minutes, from unknown sources somewhere out
there. There is some uncertainty in their energy scale (26 orders of
magnitude) and the physical mechanisms involved (with more than 120
models published in refereed journals). Recently, high-energy
emission was detected with one 10 GeV and a few 1 GeV photons detected
from GRBs. This is highly significant because it constrains the
bright bursts to have a cosmological redshift less than 80. (For
comparison, the most distant objects known are quasars out at redshift
~4.) (At redshift greater than 80, the cosmic blackbody radiation
opaque by pair production to 10 GeV photons.) This is the best upper
limit we have on the distance scale, and can exclude things like
interacting cosmic strings.
In this thread, I think Henry Spencer suggested that a litmus test of
super-advanced alien intelligences would be that they could tell us
where GRBs come from. Others expressed doubt that they would know.
(As to suggestions that the aliens cause the GRBs with their
star-drives or weapon systems, I can only point out that most occur
off the known spacelanes, with no concentrations near Tau Ceti nor
Zeta Reticuli (and you know the Greys would have that sort of thing if
anyone would.))
One of the main strategies for trying to figure out what GRBs are is
to locate them precisely, then point instruments which use other
wavelengths at that position and see what's there.
To get the location of gamma-ray burst, you need either a
direction-sensitive detector, or a set of timing measurements from
three different locations separated by interplanetary distances.
BATSE on the Compton Gamma-Ray Observatory can determine the direction
of a GRB to within 5 degrees. Other instruments can locate
bright-enough bursts in their fields of view to less than a degree.
No single instrument currently in space can get to the arc-minute
accuracy you need to just point a telescope, and say that whatever
strange thing is within the error box is the source of the GRB.
Timing the burst with three different instruments spread across the
solar system does give you a position (a pair of positions, actually,
but there is usually enough other information to disambiguate it) to
within an arc-minute or so. However, there is a GRB detector on
Ulysses, currently in a 5ish AU solar polar orbit, and a flock of GRB
detectors in near-Earth orbit. Together, these can only determine an
annulus on the sky containing the burst (although with the help of
position-sensitive single instruments, this can be reduced to a
rectangular error box a few arcminutes wide and a degree or so long).
The third instrument in the interplanetary network was on Mars
Observer, and is unlikely to be usable in the future. Until another
interplanetary GRB detector goes up, there will be no new
high-accuracy position determinations.
We have looked at previously determined small error boxes in radio,
X-ray, optical, infrared, ultraviolet, gamma-rays etc. and we have
found nothing. There are the normal number of stars, radio sources,
galaxies, etc in the error boxes (with the smaller error boxes having
none at all and the larger error boxes having them in proportion to
their area) but nothing unusual, and no type of object which appears
preferentially in the error boxes.
There is more data coming in but, so far, counterpart searches have
not shown what GRBs are, only what they are not. (They are not
associated with radio bright quasars or galaxies, pulsars, Milky Way
sized galaxies, nearby galaxies, globular clusters, giant moleular
clouds, planetary nebulae, clusters of galaxies, bright stars, flare
stars, etc.)
So, if there are any aliens out there, let us know.
--
David M. Palmer [email protected]
[email protected]
Clipper: Privacy for people who have nothing to hide.
|
| 636.66 | Compton Reboost Planned | CXDOCS::J_BUTLER | E pur, si muove... | Wed Oct 06 1993 18:16 | 87 |
|
Paula Cleggett-Haleim
Headquarters, Washington, D.C. Oct. 4, 1993
(Phone: 202/358-0883)
Michael Finneran
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-5565)
RELEASE: 93-179
COMPTON GAMMA-RAY OBSERVATORY TO GET ORBIT BOOST
NASA's Compton Gamma-Ray Observatory will receive a
scheduled boost to a higher orbit beginning today to prevent
the spacecraft from reentering the Earth's atmosphere.
The observatory will be nudged to the higher orbit in two
phases using computer commands sent to onboard rocket thrusters
from NASA's Goddard Space Flight Center, Greenbelt, Md., which
manages the spacecraft.
"The reboost is necessary to compensate for orbit decay,
which is the result of solar activity slowly pushing the
satellite toward Earth over a period of time," said Goddard's
Tom LaVigna, the former Deputy Project Manager for the
observatory who has retained management responsibility for the
reboost. "This was a known occurrence and was taken into
consideration in the design
of the observatory."
The first phase of the reboost is scheduled for Oct. 4 to
17; the second from Nov. 22 to Dec. 3, LaVigna said. The first
phase will lift the 2-year-old satellite to 280 miles (450
kilometers) at its apogee or highest point in orbit. The second
phase will circularize the orbit by boosting the spacecraft's
perigee, or lowest point, to the same elevation.
As of late September, the spacecraft was 217 miles (345
kilometers) above the Earth in an orbit that follows the
equator. Below 180 miles (290 kilometers), the satellite could
lose the stability required for reboost, LaVigna said. If the
observatory was not reboosted, he said, it would reach that
altitude in late April of 1994.
The October-November reboost will follow an attempt that
began June 15 but was terminated the same day because of a
problem with one of the thrusters on the satellite. NASA
officials discovered that the B2 attitude control thruster was
performing well below the other thrusters on the "B" side of
the observatory, making it difficult to properly control the
spacecraft. While the B2
thruster performance remains low, it has been taken into
account for the reboost.
"Extensive analysis and simulations have been performed
to develop the plan for reboost," LaVigna said.
The observatory has eight attitude control thrusters and
four larger orbit adjust thrusters, with half of each split
between the "A" and "B" sides of the spacecraft. The B-side
attitude control and orbit adjust thrusters will be used for
both phases of the reboost. During the previous reboost
attempt, only the
attitude control thrusters were planned for use.
Science operations on the observatory will be suspended
only during the actual reboost operations.
The Compton Gamma-Ray Observatory is managed by Goddard
for the Office of Space Science at NASA Headquarters in
Washington, D.C. The 17-ton observatory was launched April 5,
1991, on the Space Shuttle Atlantis and is the heaviest
civilian spacecraft deployed by a shuttle.
The $550-million observatory, a collaboration between the
United States, Germany and The Netherlands, has a mission goal
of 2 to 6 years and carries four science-gathering instruments.
The satellite exceeded its minimum life in April this year.
The observatory was sent aloft to study the gamma-ray
universe. Gamma rays are the highest energy radiations in the
electromagnetic spectrum, created by some of the most violent
events in the Universe, such as the explosion of stars. Gamma-
rays can be studied effectively only from space because the
Earth's atmosphere prevents them from reaching the ground.
|
| 636.67 | Gamma-Ray Observatory produces three major discoveries | PRAGMA::GRIFFIN | Dave Griffin | Wed Oct 13 1993 10:03 | 105 |
| Sarah Keegan
Headquarters, Washington, D.C. October 12, 1993
Michael Finneran
Goddard Space Flight Center, Greenbelt, Md.
RELEASE: 93-182
NASA's Compton Gamma-Ray Observatory has yielded three major
breakthroughs, two of which will enable scientists to unmask hidden supernovae
-- the remnants of exploded stars -- buried deep in the center of the Milky
Way. The third discovery pinpoints a source of the mysterious cosmic rays in
this galaxy that have puzzled researchers since the rays first were detected
more than 80 years ago.
The findings were made by the Imaging Compton Telescope (COMPTEL), one
of four instruments on the observatory, managed by NASA's Goddard Space Flight
Center, Greenbelt, Md.
"With these three observations, COMPTEL certainly has achieved a major
breakthrough," said Dr. Volker Schoenfelder, of the Max Planck Institut in
Germany and Principal Investigator for COMPTEL. The instrument is a
collaborative project by Max Planck, the Space Research Organization of The
Netherlands in Leiden, the European Space Agency's European Space Research and
Technical Center in The Netherlands and the University of New Hampshire in
Durham.
"The first two observations are among the first quantitative tests of
the whole theory of the origin of the elements in the universe, which are the
building blocks upon which everything we are made of are created," Schoenfelder
said. "The third discovery gives us a source for something that has eluded
astrophysicists for more than 8 decades. So it's all quite exciting."
Two of the COMPTEL discoveries were the detection of Titanium 44 and
Aluminum 26 emissions called gamma-ray lines. Titanium 44 and Aluminum 26 were
radioactive isotopes which, when they decayed, left an interstellar trail of
crumbs that COMPTEL scientists traced to the supernovae that produced the
emissions long ago.
The Titanium 44 gamma-ray line was observed from the supernova remnant
Cas-A, the leftover from a star that exploded in the mid-1600s some 9,000
light- years from Earth. A Titanium 44 gamma-ray line never had been observed
by any space- or ground-based telescope until COMPTEL's powerful detector
picked it up earlier this year.
The isotope's relatively short half-life of 54 years -- the time it
takes to radioactively decay into another chemical element -- means that
scientists now will be able to look for Titanium 44 as evidence of
comparatively recent supernovae that thus far, have eluded detection optically
or with instruments that probe wavelengths in other than the visible spectrum.
Such an ability is significant because observed supernovae in the Milky
Way are rare compared to those sighted in other galaxies. Supernovae in other
galaxies have been observed on average three times a century. By contrast, the
last recorded supernova in the Milky Way was nearly 400 years ago, in 1604.
Elements Will Serve As Beacons
Researchers have speculated, however, that many more supernovae occur
in the Milky Way but cannot be seen because of obscuring gas and dust that lies
between Earth and the star-packed inner regions of the galaxy.
"But with Titanium 44 as a beacon, COMPTEL and future experiments
should be able to detect more of those hidden supernovae," said Schoenfelder.
Unlike Titanium 44, Aluminum 26 emissions have been detected
previously. Now COMPTEL scientists have found indications that link Aluminum
26 emissions to a supernova called Vela that took place some 10,000 years ago
about 1,000 light-years away.
If this finding is verified by further analysis, then COMPTEL would
have, for the first time, established a link between Aluminum 26 emissions and
a supernova. This in turn would allow scientists to discover more supernovae
that occurred in the much more distant past, due to the very long half-life --
about 1 million years -- of Aluminum 26.
COMPTEL's third discovery was to identify the Orion nebula, an area of
molecular clouds and star-forming regions, as a source of cosmic rays. Cosmic
rays are high-speed particles that fill the Milky Way galaxy. They were
discovered in 1911, and scientists ever since have searched in vain for their
sources.
COMPTEL, however, identified a region in which cosmic rays are
abundant. These cosmic rays were detected through their interaction with other
particles in space.
As the chemical elements that make up these rays were accelerated by
supernovae explosions and stellar winds, the chemical elements collided with
gas between stars in the Orion nebula at velocities up to the speed of light --
186,000 miles per second. The collisions caused them to emit gamma-ray lines.
COMPTEL detected gamma-ray lines for carbon and oxygen that were produced by
these particle collisions.
"It is now a challenge for theorists to explain what produces cosmic
rays," said Schoenfelder. Most likely, they are created by the young stars in
the Orion nebula. But no one is certain.
The observatory was launched April 5, 1991, on the Space Shuttle
Atlantis. It is managed by Goddard for the Office of Space Science, NASA
Headquarters, Washington, D.C.
|
| 636.68 | GRO Reboost Successful | PRAGMA::GRIFFIN | Dave Griffin | Tue Dec 21 1993 09:28 | 98 |
| Donald L. Savage
Headquarters, Washington, D.C. December 20, 1993
Michael Finneran
Goddard Space Flight Center, Greenbelt, Md.
RELEASE: 93-224
NASA has successfully boosted its Compton Gamma-Ray Observatory into a
higher orbit around the Earth, a move that will keep the 17-ton satellite from
reentering the atmosphere.
The reboost is a significant accomplishment because it extends the mission
life of the observatory by 5 years and prevents a reentry in which large parts
from the spacecraft could have struck Earth, said officials at the Goddard
Space Flight Center in Greenbelt, Md., which manages the spacecraft.
The observatory was sent aloft to study the gamma-ray universe. Gamma rays
are the highest energy radiations in the electromagnetic spectrum, created by
some of the most violent events in the universe, such as the explosion of
stars. Gamma- rays can be studied effectively only from space because Earth's
atmosphere prevents them from reaching the ground.
The reboost, which was concluded Dec. 17, had been anticipated when the
2-year-old spacecraft was designed. It was necessary because of solar activity
that slowly pushed the satellite back toward Earth. Initially scheduled earlier
in the mission, the reboost was delayed because of the high risk of operating
the spacecraft's propulsion system after a problem that occurred shortly after
launch.
"Although this reboost was always planned, its successful completion
involved solving some complex problems never before encountered by NASA," said
Goddard's Tom LaVigna, former deputy project manager for the observatory, who
retained management responsibility for the reboost.
NASA managers had to compensate for a balky rocket thruster on the
observatory, LaVigna said, and devise a new way to inject fuel into the
sensitive plumbing lines leading to the thrusters.
The complex procedure for boosting Compton was developed by Goddard
engineers after extensive analysis and simulations. It employed a novel way to
operate the observatory propulsion and the attitude control subsystems together
to achieve a controlled boost.
The observatory has the largest propulsion system ever launched by NASA,
carrying 4,200 pounds (1,910 kilograms) of propellant. It has 8 attitude
control thrusters and four larger orbit adjust thrusters, with half of each
split between the "A" and "B" sides of the spacecraft.
Through mathematical analyses and tests, it was determined that very high
fuel-line pressure surges had compromised the A- side propulsion system when
the system was first operated, shortly after launch. After extensive study and
testing, a unique fuel-line priming procedure was developed to prepare the
redundant B-side thrusters for use in the reboost.
The priming worked well, but the reboost was terminated when the B2
attitude control thruster performed significantly below the other thrusters and
caused the observatory to go unstable and tumble. Quick action by ground
controllers terminated the thruster firings and, using a contingency procedure,
brought the observatory back into a stable mode.
With the standard procedure no longer usable, Goddard engineers developed a
novel way around the problem. The procedure involved firing 2 of the 4
100-pound orbit adjust thrusters for 60 to 90 seconds. The 5-pound attitude
control thrusters and reaction wheels were used together to limit unstable
conditions and errors in pointing the observatory. A total of 18 propulsion
system burns were used, one each day.
The reboost was accomplished in two phases, one that concluded in October
and another spanning November and December. The first phase lifted the
observatory's apogee -- or highest point in orbit -- to 280 miles (452
kilometers). The apogee had descended to 214 miles (346 kilometers). The
two-part second phase of the reboost nudged the spacecraft's perigee -- lowest
point -- to the same 280 miles, making Compton's orbit around the Earth almost
perfectly circular.
If the satellite had descended below 180 miles (290 kilometers), it could
have lost the stability required for reboost, LaVigna said. If the observatory
was not reboosted, he added, it would have dropped to that altitude in late
April of 1994.
When the gamma-ray observatory's life is over, NASA managers plan a
controlled reentry so that the unburned debris falls harmlessly on an
uninhabited area.
The $550-million observatory, a collaboration between the United States,
Germany and The Netherlands, has a mission goal of 2 to 8 years and carries
four science-gathering instruments. The satellite exceeded its minimum life
requirement of 2 years in April 1993.
The Compton Gamma-Ray Observatory is managed by Goddard for the Office of
Space Science at NASA Headquarters in Washington, D.C. The observatory was
launched April 5, 1991, on the Space Shuttle Atlantis and is the heaviest
civilian spacecraft ever deployed by a shuttle.
|
| 636.69 | Another twist in the the GRB mystery.... | PRAGMA::GRIFFIN | Dave Griffin | Mon Jan 17 1994 17:36 | 134 |
| [... and potentially another great feather in GRO's cap. -dg]
Brian Dunbar
Headquarters, Washington, D.C.
January 15, 1994
(Phone: 202/358-0873)
Michael Finneran
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-5565)
RELEASE: 94-10
SATELLITE FINDS IMPRINT OF UNIVERSE ON GAMMA-RAY EXPLOSIONS
Astronomers have uncovered new evidence that huge explosions, known as
gamma-ray bursts, occurred in the far reaches of the universe and bear an
imprint of the universe's expansion.
Analysis of data from NASA's Compton Gamma Ray Observatory satellite by a
team led by Dr. Jay Norris of Goddard Space Flight Center, Greenbelt,
Md., now indicates that gamma-ray bursts show relative "time-dilation."
This is an effect that would be created by many of the bursts occurring
so far away in the universe that time is seen to be running noticeably
slower there.
Time dilation is a consequence of the General Theory of Relativity and
the expansion of the universe. Thus, time intervals from very distant
parts of the universe will be stretched as the gamma-ray bursts make
their way across the expanse of space, which is itself expanding.
This much sought-after result provides additional evidence that gamma-ray
bursts are not limited to the area of the Milky Way galaxy as some
researchers have suggested.
"This is a great result, one of the most spectacular astrophysical
discoveries of the decade," said Professor Bohdan Paczynski of Princeton
University. Paczynski and Dr. Tsvi Piran of Harvard University and
Hebrew University of Jerusalem had previously predicted the effect in
gamma-ray bursts.
Norris was cautious about the meaning of time-dilation. "Our result
should not be taken as proof that the time-dilation is a result of
cosmological expansion of the universe -- just that a difference in
durations of bright and dim bursts does exist and must now be accounted
for by any theory," Norris said.
"If time-dilation is a result of cosmology," added Goddard-based Dr.
Robert Nemiroff of George Mason University and a member of the Norris
team, "then this is not only an important discovery about gamma-ray
bursts, it is a discovery that gamma-ray bursts may be able to tell us
about distant parts of our universe."
The Norris team, which includes astrophysicists at Goddard and NASA's
Marshall Space Flight Center, Huntsville, Ala., NASA's Ames Research
Center, Mountain View, Calif., and the University of Pennsylvania,
uncovered gamma-ray burst time-dilation in two ways.
First, they showed that dim bursts typically have twice the duration of
bright gamma-ray bursts. Next, they showed that dim bursts typically are
"redder" in gamma-ray color than bright bursts, an effect that is a
direct result of time-dilation on the gamma-ray burst spectrum.
Norris stressed that while the time-dilation effect itself is well
quantified, the spectral difference, though very significant, is yet to
be calibrated.
Bursts Outshine Entire Gamma-Ray "Sky"
Gamma-ray bursts are huge explosions that have been detected only in the
gamma-ray region of the spectrum. Some last only a fraction of a second,
but others are as long as a few minutes. A gamma-ray burst explosion
dramatically outshines the entire sky in the gamma-ray band.
The origins of gamma-ray bursts have been an enigma since their discovery
in the late 1960s by U.S. defense satellites. But the Compton Gamma Ray
Observatory has allowed astronomers to study these bursts in more detail
than ever. Until Compton's observations of hundreds of bursts, it was
widely believed that the sources of these powerful phenomena were in the
Milky Way galaxy.
The celestial distribution of gamma-ray bursts is uniform unlike the
appearance of the Milky Way galaxy, which looks like a band in the sky.
The fact that gamma-ray bursts come from all directions is what
originally suggested a cosmological, or extra-galactic, origin, and so a
search for time-dilation began.
If the time dilation measured by Norris's team is a good indication of
gamma-ray burst distance, then these bursts are occurring far into the
universe. In addition, for Compton to see them as bright as they are,
the power of these explosions may be greater than anything ever seen
before, as much as one quintillion suns.
The astronomical community is cautious about accepting this result
blindly. "I like to think I'm objective," said Dr. Thomas Cline, a long-
time gamma-ray burst researcher at Goddard, "and although the outcome of
this analysis is consistent with the hoped-for time-dilation effect, I'm
still concerned that it might result from a real but misleading feature
of the changing luminosity of gamma-ray bursts or a misleading but unreal
feature of the data or the satellite. That, of course, only heightens the
mystery."
"We've found time-dilation using several statistical tests," said Norris,
who then listed several detailed mathematical and statistical tests that
were performed on the data. The spectral difference between bright and
dim bursts, also seen in a statistical sense, was found by comparing the
spectral "colors" of bursts across the durations of gamma-ray burst
events.
Dr. Virginia Trimble of the University of Maryland and California,
Irvine, said: "For more than 50 years, astronomers have been looking for
objects or phenomena whose observed properties are dominated by the large
scale evolution and structure of the universe ('cosmological effects')
rather than by observational selection or the detailed evolution of the
individual objects. If the gamma bursts have indeed revealed such
cosmological effects, then this is perhaps even more important as an
astrophysical 'first' than as a contribution to our understanding of the
bursters themselves."
The Norris team analyzed data from Marshall's Burst and Transient Source
Experiment (BATSE) on board Compton, whose principal investigator is Dr.
Gerald Fishman. The Compton Gamma Ray Observatory, deployed from the
Space Shuttle Atlantis on April 7, 1991, is managed by Goddard for the
Office of Space Science at NASA Headquarters, Washington, D.C.
Editors Note: The subject of this release will be discussed at
a press conference at the American Astronomical Society meeting
on Saturday, Jan. 15, at 9:20 a.m. in the Alexandria Room of
the Crystal Gateway Marriott, Arlington, Va.
|
| 636.70 | Repeating gamma-ray bursts | JVERNE::KLAES | Be Here Now | Wed Mar 16 1994 14:38 | 379 |
| Article: 54153
From: [email protected] (James Vanmeter)
Newsgroups: sci.astro
Subject: Gamma Ray Bursts
Date: 11 Mar 1994 21:38:55 GMT
Organization: University of California; Santa Cruz
There's a recent (Dec.'93) analysis of the gamma-ray burst data
by R. Narayan and T. Piran ("Do Gamma-ray Burst Sources Repeat?",
Mon.Not.R.Astron.Soc. v265,pL65) with some very interesting
results. I'll quote the abstract and conclusion:
"Following the discovery by Quashnock & Lamb of an apparent
excess of gamma-ray burst pairs with small angular separations,
we reanalyse the angular distribution of the bursts in the BATSE
catalogue. We find that, in addition to an excess of close pairs,
there is also a comparable excess of antipodal bursts, i.e. pairs
of bursts separated by about 180^o in the sky. Both excesses are
moderately significant. Quashnock & Lamb argue that the excess of
burst pairs with small angular separations is evidence that many
bursts repeat, but obviously this hypothesis cannot explain the
excess of antipodal coincidences. Since the two excesses have
similar characteristics, and since we cannot think of any physical
model of bursts that can produce antipodal pairs, we suggest
that both excesses may be due to some unknown selection effect."
"The main result of this paper is that there are actually
two independent excesses in the angular correlation function of
gamma-ray bursts: an excess of nearby neighbors within 4^o (as
discovered by QL), and an additional excess of farthest neighbors
(>176^o). We have been unable to come up with any physical model
that can explain an excess of bursts within 4^o of the antipode.
Obviously, a population of repeaters cannot produce this effect.
An antipodal excess may occur if the bursts are located along a
narrow line in space or in a very thin disc. Such distributions,
however, are ruled out by the observed overall isotropy of the
positions of the bursts (Meegan et al. 1992), and inhomogeneities
in the BATSE sky coverage occur on much too wide an angular scale
to produce features with a width of only 4^o.
"Considering the strong similarity of the two excesses, we
think that one should seek a common explanation for the two
peaks. Occam's Razor too would argue for a single effect. Since
we have been unable to come up with any physical model that can
produce the antipodal excess, we conclude that the excess of close
pairs of bursts discovered by QL and the antipodal excess that we
discuss here are both caused by some selection effect, unless
they are due to an unusual statistical fluctuation. We do not
have any specific idea as to the nature of the selection effect."
I have an idea. These repeating, gamma-ray burst-sources seem
to choose each other as targets, and this is a common enough
phenomenon that Earth frequently finds itself in the cross-fire;
hence the detected "antipodal pairs". I hope you see what I'm
suggesting. But perhaps I am losing my head in Occam's Guillotine?
Article: 54154
From: [email protected] (John McDonald)
Newsgroups: sci.astro
Subject: Re: Gamma Ray Bursts
Date: 11 Mar 1994 22:27:58 GMT
Organization: San Diego State University, College of Sciences
James Vanmeter ([email protected]) wrote:
: I have an idea. These repeating, gamma-ray burst-sources seem
: to choose each other as targets, and this is a common enough
: phenomenon that Earth frequently finds itself in the cross-fire;
: hence the detected "antipodal pairs". I hope you see what I'm
: suggesting. But perhaps I am losing my head in Occam's Guillotine?
I have an idea too, suppose they are the same location on the very
opposite sides of the spherical universe, and we are seeing the
same burster from both directions on the universal 4-D sphere!
John
Article: 54193
Newsgroups: sci.physics,sci.astro
Subject: Re: Gamma Ray Bursts
From: [email protected] (Sean Carroll)
Date: 12 Mar 1994 17:53:09 GMT
Organization: Harvard University, Cambridge, Massachusetts
Before this gets out of hand, I think that John's initial reaction
was essentially correct. Piran and Narayan are essentially saying
"Quashnock and Lamb claim to find an apparent correlation in
the excess of nearby gamma-ray bursts, which you might be tempted
to interpret as something significant about the nature of the
bursts. As a check, we look for correlations between antipodal
bursts, which you should not be tempted to think of as anything
about the sources at all, but something about the sampling method
or statistical procedure. Since we find that there is such a silly
correlation, we caution you not to take the correlation between
nearby bursts too seriously." A paraphrase, but I think this has
the idea essentially correct. (I'm crossposting to sci.astro,
where people might have more details.)
I think that Piran and Narayan would be horrified if someone (such
as the person referenced by Jarle Brinchmann in another post) took
their results as evidence for a topologically nontrivial Universe
(on large scales). By the way, there have been hard looks at the
idea of a non-simply connected cosmology, and a recent paper (by
Silk and others) claims that the isotropy of the microwave
background puts very stringent limits on the "periodicity" (or,
if you like, translational part of the ISO(3) holonomy around
a constant-time spacelike hypersurface :-]).
--Sean
Article: 54209
From: [email protected] (James Vanmeter)
Newsgroups: sci.physics,sci.astro
Subject: Re: Gamma Ray Bursts
Date: 13 Mar 1994 05:21:07 GMT
Organization: University of California; Santa Cruz
OK, I will humbly retract the ET-communication hypothesis, for
the moment. But a few points need clarification, so here's more
quotes from the Naryayan & Piran article:
"We repeat here the nearest neighbor analysis employed by
QL, and add to it another analysis based on the more standard
angular autocorrelation function. We find that, while there does
appear to be an excess of close pairs of bursts with angular
separation less than 4^o, as claimed by QL, there is also an
equivalent excess of antipodal pairs of bursts with angular
separations larger than 176^o."
"A data set composed of randomly positioned sources, some
of which repeat, has a simple angular correlation function: a
delta-function peak at the origin due to the repeaters, and a
slightly negative constant elsewhere. Errors in position
measurements will spread out the delta function to a broadened
peak at the origin, with a width and shape determined by the
probability distribution of the positional errors, but nowhere
else other than at the origin do we expect any significant
peak or dip. This simple structure of the two-point correleation
function suggests that it should be a clean statistic with which
to test the repeating source hypothesis.
"The correlation function of all the 260 bursts in the
BATSE catalogue is shown in Fig.1. As expected from the QL
analysis, there is a peak in the bin corresponding to theta<4^o.
To assess the statistical significance of this peak, we have
carried out Monte Carlo simulations with 10,000 random samples.
From this we estimate that the peak has an amplitude of 1.75
standard deviations, and that the probability of obtaining
by chance a peak as strong as or stronger than the observed
one is .0957 (9.57%)."
"While the existence of a peak at theta < 4^o agrees
with the QL result, there is another unexpected peak at the
antipode, corresponding to the bin with theta > 176^o. The second
peak is slightly wider than the peak at the origin and has an
amplitude of 1.86 standard deviations, which is marginally more
significant (probability = .0724) than the direct peak. In fact,
while the statistical significance of each of the single peaks
is only moderate, the statistical significance of having both
peaks is much higher."
"When we eliminate bursts with Poisson positional errors
delta-theta > 4^o (which corresponds to total errors
delta-theta-tot > 5.7^o), far from becoming stronger, the
evidence for the excesses actually becomes weaker. In fact, the
decrease in the signal is quite drastic in the case of nearest
neighbor pairs, while it is more modest for the antipodal pairs."
Article: 54239
From: [email protected] (Ethan Bradford)
Newsgroups: sci.astro
Subject: Re: Gamma Ray Bursts
Date: 14 Mar 1994 02:38:46 GMT
Organization: University of Washington
In article <[email protected]> [email protected]
(John F Carr) writes:
> Can a single gamma ray detector distinguish between bursts from
> opposite directions?
BATSE consists of eight detectors on the corners of GRO. By comparing
their signals one can locate the burst to within several degrees.
Article: 54293
From: [email protected] (David M. Palmer)
Newsgroups: sci.physics,sci.astro
Subject: Re: Gamma Ray Bursts
Date: 14 Mar 1994 20:40:26 GMT
Organization: California Institute of Technology, Pasadena
[email protected] (Matt McIrvin) writes:
>Hmmm, about these mysterious antipodal correlations... I know basically
>nothing about gamma-ray telescopes, but is there some possibility that one
>could get the position of a source wrong by 180 degrees? I suppose the
>possibility of this becomes rather slim if the telescope is in low earth
>orbit-- were the antipodally correlated bursts near the horizon when they
>were detected?
The instrument in question, BATSE on the GRO satellite, consists of 8
radiation detectors pointed in all directions (as the faces of an
octahedron), and shielded in back. The detectors which face within 90
degrees of the burst detect the radiation (with the strength of the
signal depending on how closely it face the burst) while those which
are pointed away from the burst do not see it. Also, as you pointed
out, the Earth blocks out almost half the sky, and so the antipodal
point is typically blocked.
When each burst is detected, the direction to Earth is an important
part of the postioning algorithm. (Gamma-rays scattered off Earth's
atmosphere can get into detectors even when they are pointed away from
the burst.)
BATSE has detected bursts of gamma-rays coming from Earth. These seem
to be associated with lightning storms. Nobody understands the
mechanism yet, but I expect that a good theory for this will come
before a good theory of GRBs.
--
David M. Palmer [email protected]
[email protected]
Clipper: Privacy for people who have nothing to hide.
Article: 54366
Newsgroups: sci.astro
From: [email protected] (Steve Horsley)
Subject: Re: Gamma Ray Bursts
Organization: Home
Date: Tue, 15 Mar 1994 08:47:02 +0000
Sender: [email protected]
In article <[email protected]>
[email protected] "John McDonald" writes:
> I have an idea too, suppose they are the same location on the very
> opposite sides of the spherical universe, and we are seeing the
> same burster from both directions on the universal 4-D sphere!
I like the idea, but I think it cannot be right - here are two reasons why,
based on Stephen Hawkings' Brief History Of Time:
* The universe is only a closed hypersphere if it is going to re-collapse
one day. Currently, we're struggling to find enough mass to stop the
universes' infinite expansion.
* Even if the universe is closed, Hawking says it can be shown that
nothing could circumnavigate it before it recollapsed, even at C.
I assume therefore that since the universe is still expanding, nothing
could have got halfway round yet, so we cannot be seeing bursters from
both directions.
Two more reasons I just thought of...
* If the burster was dead opposite, wouldn't we see the burst from ALL
3D directions?
* The chance of so many bursters being so close to opposite us that the
path difference is within the short experiment duration seems a little
unlikely.
--
Steve Horsley [email protected]
Article: 54202
From: [email protected] (David M. Palmer)
Newsgroups: sci.physics,sci.astro
Subject: Gamma Ray Bursts
Date: 13 Mar 1994 02:02:19 GMT
Organization: California Institute of Technology, Pasadena
There has been some discussion in these groups recently about gamma-ray
bursts. I'll just address the points that have been raised, so this
will be somewhat disjointed:
First of all, there are two different types of flashes of gamma-rays
coming from the sky: Classical Gamma Ray Bursts (GRBs) and Soft Gamma
Repeaters (SGRs). SGRs come repeatedly from a few points in the sky,
have relatively uniform pulses of about a tenth of a second each and
peak energies of a few tens of keV. Each GRB, as far as we know, comes
from a different source, they have durations from ten of milliseconds
to ten minutes, a huge variety of lightcurve shapes, and peak energies
of a few hundred keV.
Taking SGRs first: There are three known sources of these flashes.
One is in the direction of the Large Magellanic Cloud (LMC), and more
specifically, is in the direction of a supernova remnant (N49) in the
LMC. This source also produced the (EXTREMELY INTENSE) March 5 burst.
The second source is in the direction of the Galactic bulge, and is
coincident with a supernova remnant beyond the bulge. A few months
ago, this source was active again, and an imaging X-ray telescope
pointed at the supernova remnant and saw it flash. The third source is
also in the plane of our Galaxy, but it currently has too large an
error box to say more than its posistion is consistent with serveral
supernova remnants.
The March 5 event had a clear 8-second periodicity, like a pulsar.
That and the association with supernova remnants, is pretty convincing
evidence that SGRs are neutron stars.
GRBs are more mysterious.
GRBs are distributed evenly in all directions in the sky, but there are
fewer dim (distant) ones than you would expect from the number of
bright (nearby) ones, leading to the conclusion that we are near
(within a tenth of a radius) the center of a finite spherical
distribution of the sources. We do not know what 'distant' and
'nearby' mean in terms of A.U., light-years, or megaparsecs, we just
assume the dimmer ones are farther away than bright ones. The
distribution is inconsistent with any population of known sources
distributed in our Galaxy. It is not inconsistent with a population of
sources centered around our Sun with a typical distance of hundreds of
Astronomical Units, but nobody has any reasonable ideas on how to get
gamma-ray bursts from Oort-cloud objects. The data is also consistent
with a 'cosmological' distribution, with the faintest bursts we can see
having a distance expressed as a redshift of z~1.
A redshift of z~1 means that all energies are decreased by a factor of
1+z=2, and that the development of the GRB is slowed by the same
factor. This is what the recent results of Norris, Nemiroff, and Davis
seem to show. However, there are uncertainties in this result. GRBs
are extrememly variable in both energy and time behaviour. It may be
that the dim bursts, which they found to be lower in energy and slower
in development, are that way because they are intrinsically dimmer: if
you have a fire log burning low, the flame will be redder and last
longer than it would if it were burning more actively. However, the
fact that the results match the predictions of the cosmological
distance scale is encouraging.
If GRBs are at such large distances, then the emitted energy of a burst
is comparable to the energy of a supernova, and most models call for at
least the total disruption of a star (e.g. two neutron stars spiraling
into each other). This is not the sort of thing that is likely to
happen twice in the same system. Therefore, if two GRBs are seen from
the same location, this would be evidence that they are not
cosmological. Quashnock and Lamb claim that the BATSE data shows that
sources are repeating. However, this result is dubious for several
reasons, including the fact that the data show even stronger evidence
that GRBs are followed by GRBs 180 degrees away in the sky, suggesting
that the result is an artifact. Also, the evidence goes away when a
larger data set is used. A good summary of this dispute is given in a
Commentary by Brad Schaefer in Nature a few weeks ago.
The dataset used by Quashnock and Lamb is available from the GRO
science support center, so if you are interested, grab it and start
playing. (Telnet to GROSSC.gsfc.nasa.gov with username gronews, and
get the BATSE catalog.)
The status of cyclotron lines is also unclear. These are absorption
lines in a GRB's spectrum from absorption by electrons in a 10^12 gauss
magnetic field. (The only known source of 10^12 gauss fields is
neutron stars.) The data from the Ginga satellite is pretty
convincing. However BATSE, which has seen many more GRBs than Ginga,
has not found lines. These results are still consistent at the 10%
level, but the discrepancy is worrisome.
The suggestion that GRBs are the blasts of Hawking radiation emitted by
evaporating black holes is one of the few of the 100+ GRB models which
has been rejected. All black hole evaporations look the same, because
'black holes have no hair' which would make them look different. GRBs
all look different. A GRB evaporation would appear as a brief
(milliseconds-long) burst of radiation rising rapidly in energy.
People are searching the GRO data for such bursts, but haven't found
any yet.
Unlike SGRs, when we look at the locations of GRBs, we see nothing.
Quite a few small (<1 small arc-minute) error boxes have been observed
with optical, radio, IR, UV and X-ray instruments. There's just
nothing there (apart from the typical background objects you would get
if you just chose a random square arcminute in the sky and examined it
intently). This means that if GRBs are found in external galaxies,
those galaxies are pretty darn inconspicuous. Quasars, Seifferts, or
other active galaxies, or even galaxies the brightness of ours, are all
absent from the GRB locations.
--
David M. Palmer [email protected]
[email protected]
Clipper: Privacy for people who have nothing to hide.
|
| 636.71 | Gamma-ray flashes high above Earth thunderstorms | MTWAIN::KLAES | Keep Looking Up | Tue Jun 07 1994 00:18 | 67 |
| From: US4RMC::"[email protected]" "Peter Yee" 3-JUN-1994 21:00:52.59
To: [email protected]
CC:
Subj: Unusual high energy flashes seen in Earth's atmosphere [Release 94-86]
Brian Dunbar
Headquarters, Washington, D.C. May 27, 1994
(Phone: 202/358-1547)
RELEASE: 94-86
UNUSUAL HIGH ENERGY FLASHES SEEN IN EARTH'S ATMOSPHERE
Scientists at NASA's Marshall Space Flight Center in
Huntsville, Ala., have discovered unusual gamma-ray flashes
in the upper atmosphere high above thunderstorms.
These high energy bursts have never before been seen in
the Earth's atmosphere or surrounding space, according to Dr.
Gerald Fishman of Marshall's Space Science Laboratory.
These flashes were detected by the Burst and Transient
Source Experiment (BATSE), a Marshall instrument aboard
NASA's orbiting Compton Gamma Ray Observatory.
"It is suspected that these flashes come from a rare type
of powerful electrical discharge, similar to lightning, above
large thunderstorm regions," Fishman said. The observations
were published in this week's issue of Science, an
international scientific journal.
"The flashes are very brief, lasting only a few
thousandths of a second, although some of them consist of
multiple pulses." They are seen very infrequently: only
about twenty have been seen since the observatory was
launched in April 1991 from the Space Shuttle Atlantis.
"We saw our first flash of this type the first week that
the detectors were turned on. We didn't know what to make of
it," said Fishman. In order to detect gamma rays with space-
borne detectors, they must be produced at altitudes above
100,000 feet. This is considerably higher than normal
weather processes, according to Fishman.
The observations have been confirmed by other instruments
on the observatory. The BATSE detectors on the observatory
were originally designed for sensitive observations of celestial
objects in wavelength regions unobservable from the ground.
"The gamma-ray observations from the Earth's atmosphere
come as a complete surprise to us. Atmospheric scientists
are also surprised," said Fishman.
"For many years, aircraft pilots have reported 'upward-
going' lightning in clear air over thunderstorms. But these
reports were either never taken seriously or were never
studied in a scientific manner," he said.
In recent years, there have been video observations of
electrical discharges above thunderstorms taken from the
Space Shuttle and from research aircraft. The new gamma-ray
flash observations may be related to these optical
observations, Fishman said.
"It is becoming apparent that the upper atmosphere is much
more electrically active than we ever suspected," he concluded.
|
| 636.72 | X-Ray Nova Scorpii | MTWAIN::KLAES | No Guts, No Galaxy | Mon Aug 29 1994 16:57 | 86 |
| From: US1RMC::"[email protected]" "HILL, DIANNE" 27-AUG-1994 06:06:40.19
To: "[email protected]" <[email protected]>
CC:
Subj: 94-140 COMPTON GAMMA-RAY OBSERVATORY FINDS BRIGHT NEW X-RAY SOURCE
Donald L. Savage
Headquarters, Washington, D.C.
August 24, 1994
(Phone: 202/358-1547)
Mike Finneran
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-5565)
Jim Sahli
Marshall Space Flight Center, Huntsville, Ala.
(Phone: 205/544-6528)
RELEASE: 94-140
COMPTON GAMMA-RAY OBSERVATORY FINDS BRIGHT NEW X-RAY SOURCE
An unusually bright X-ray source -- one of the three brightest in
the sky -- has been discovered in the southern constellation Scorpius
by an instrument aboard NASA's Compton Gamma-Ray Observatory. The new
source, which was discovered on July 27 by the Burst and Transient
Source Experiment (BATSE), has been named X-ray Nova Scorpii, or GRO
J1655-40.
X-ray novae such as the one just discovered are thought to be
caused by matter spilling from a normal star onto a black hole, which
are collapsed stars so dense that not even light can escape them.
About 10 such novae have been discovered in the past 30 years.
"We are anxious to determine whether the new source is a black
hole, a pulsar (a spinning star that emits signals in short, regular
bursts), or perhaps even a new type of object," said Dr. B. Alan
Harmon of NASA's Marshall Space Flight Center, Huntsville, Ala.
Harmon leads the research team analyzing data from a Marshall-managed
BATSE instrument.
"The X-ray emission from the new source rivals that of two other
dominant X- ray sources in the sky, the Crab Nebula and Cygnus X-1.
The new object poses several puzzling questions for astrophysicists.
For example, Nova Scorpii had an unusually rapid rise to maximum
brightness, which may put significant constraints on theories of how
X-rays are produced in such objects," Harmon said.
"During an X-ray nova outburst, it is thought matter from a
normal star spills onto a disk of matter surrounding a companion black
hole, causing the disk to heat up dramatically. How this happens,
however, is not well understood, and the rapid rise to maximum
brightness of Nova Scorpii adds to the mystery," Harmon said.
In addition, a property conspicuously absent in Nova Scorpii is a
rapid flickering in the intensity of the source. Such flickering is
typical of other X-ray novae. Scientists speculate that the lack of
flickering may be because the central source that would produce it is
obscured, preventing a view deep into the X-ray producing region.
Discovery of the new X-ray object has been announced to
astronomers around the world so more detailed observations may be
made. Another instrument on the Compton Observatory, the Oriented
Scintillation Spectrometer Experiment, already has made preliminary
spectral observations and obtained an improved location for the
object. Meanwhile, plans are being made for other orbiting spacecraft
to observe the X-ray source and a search is underway by astronomers in
the Southern Hemisphere to find an optical counterpart to Nova Scorpii.
"We are especially pleased that BATSE detected the X-ray source.
Now, the entire capabilities of the observatory can be used to study
this new and exciting object," said Compton Observatory Project
Scientist Dr. Neil Gehrels of the Goddard Space Flight Center,
Greenbelt, Md.
Goddard manages the Compton Observatory for NASA's Office of
Space Science, Washington, D.C. The observatory was placed into orbit
around the Earth by the Space Shuttle Atlantis in April 1991.
% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% From: "HILL, DIANNE" <[email protected]>
% To: "[email protected]" <[email protected]>
% Subject: 94-140 COMPTON GAMMA-RAY OBSERVATORY FINDS BRIGHT NEW X-RAY SOURCE
% Date: Thu, 25 Aug 94 13:50:00 PDT
% Sender: [email protected]
|
| 636.73 | Gamma Ray flashes more common than thought | TROOA::SKLEIN | Nulli Secundus | Wed Jan 04 1995 14:25 | 63 |
| Donald Savage
Headquarters, Washington, DC December 7, 1994
(Phone: 202/358-1727)
Steve Roy
Marshall Space Flight Center, Huntsville, AL
(Phone: 205/544-6535)
RELEASE: 94-204
GAMMA RAY FLASHES IN ATMOSPHERE MORE COMMON THAN THOUGHT
Scientists at NASA's Marshall Space Flight Center in
Huntsville, AL, are observing rare gamma ray flashes above
thunderstorms at a rate six times that of previous
observations.
The observations are being made by the Burst and
Transient Source Experiment aboard NASA's Compton Gamma Ray
Observatory which was recently modified by ground commands
to be more sensitive to the events.
"The high rate of occurrence of these gamma ray
events suggests the presence of a little understood, but
significant phenomena that will have impact in many
scientific fields," explained Dr. Steve Goodman of
Marshall's Space Sciences Laboratory. "We're especially
looking forward to the opportunity to bring together
investigators from the fields of space and atmospheric
physics to study these newly discovered events."
Scientists previously observed gamma ray flashes
above thunderstorm activity about once every six weeks.
Now, they are observing such gamma ray events weekly. The
first indications of gamma ray flashes above thunderstorms
were detected by the Burst and Transient Source Experiment
earlier this year.
It is suspected the gamma ray flashes come from a
rare type of powerful electrical discharge, similar to
lightning, above large thunderstorm regions. The observed
flashes are very brief, lasting only a few thousandths of a
second. In the past two months most of the observed gamma
ray flashes have occurred near the equator, primarily over
regions of South America and the East Indies known to have
high thunderstorm activity.
These recent observations have been confirmed by
other instruments on the Compton Observatory. The gamma
ray observations from the Earth's atmosphere and their
association with thunderstorms is a complete surprise to
scientific investigators. It is suspected the gamma ray
events may be related to faint, but visible electrical
discharges observed and reported recently high in the
stratosphere above thunderstorms.
The new observations were presented at a meeting of
the American Geophysical Union in San Francisco today by
Dr. Steve Goodman. The Compton Gamma Ray Observatory is
managed by NASA's Goddard Space Flight Center in Greenbelt,
MD, and the Burst and Transient Source Experiment is
managed by Marshall.
|