| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 745.1 | .001 | TUCKER::BIRO | | Tue Aug 06 1991 09:33 | 132 |
|
ALEXIS E-mail Newsletter # 1.
Premier issue
Introduction
------------
Welcome to the ALEXIS electronic e-mail newsletter.
This informal service is designed to provide information
about ALEXIS to interested parties on a timely basis free
from the costs of typesetting and postage. It may even be
possible in the future to distribute graphical information
to those on this mailing list through the use of postscript
files. Address questions and comments to
[email protected], or [email protected], (Inter-
net) or ESSDP1::103283 (SPAN). The distribution used for
this e-mail newsletter is available by using the address
[email protected].
Current Status
--------------
The ALEXIS spacecraft is currently assembled and
sitting the clean room at our facility at LANL. It has just
come back from Sandia National Laboratory (SNL) in Albu-
querque where it underwent mass properties measurements for
the whole satellite and an antenna test for the piggyback RF
experiment called Blackbeard. The satellite will undergo
three full functional checkouts which will include tests for
the experiments before going back to SNL for final environ-
mental tests. There will also be a local RF telemetry test
using the actual ground station here at Los Alamos. Our re-
quested launch date is September 18, (1991) from a Pegasus
launch vehicle. This operation takes place at Edwards AFB
and the NASA Dryden Flight Center. The B-52 used to launch
Pegasus is the same one that was used to drop the X-15 rock-
et plane.
Will we make it? One key thing to watch is the
second flight of Pegasus, scheduled for July 17. We are the
third flight and I think the feeling is that there needs to
be 60 days between flight 2 and 3. So if flight 2 is signi-
ficantly delayed, we could be also. Stay tuned to CNN for
details I guess...
A Brief History of ALEXIS
-------------------------
Some of you may be wondering what ALEXIS is and how
it came to be. ALEXIS stands for Array of Low Energy X-ray
Imaging Sensors. It is used in two senses, first as the name
for the entire spacecraft, and second as the name of one of
two experiments on the spacecraft. The ALEXIS spacecraft has
a primary experiment consisting of six small EUV/Ultra-soft
July 29, 1991
- 2 -
X-ray telescopes and a secondary piggyback RF experiment
called Blackbeard.
The ALEXIS satellite is funded by the Department of
Energy as a technology development mission. The launch is
being funded by the Air Force Space Test Program. This means
that we get the bucks to prove that small, wide-field of
view X-ray telescopes like these can work on orbit and that
small satellites can be effective means to prototype new
sensor technology on a fast time scale. So astrophysical
sources of X-ray and EUV radiation are a means to an end, as
far as the DOE is concerned, to prove the working charactis-
tics of this technology. However, we have had the forsight
to realize that a significant amount of astrophysics can be
done with this mission if everything works right.
ALEXIS started 3-1/2 years ago as a paper study of
how to fly several wide-field-of-view multilayer mirror
telescopes on a small satellite. Soon after, a design effort
was underway for the experiment and the supporting electron-
ics. We then obtained prototype detectors and mirrors for
evaluation. Our sister laboratory, SNL, agreed to design
and construct the data processing unit for the experiment.
A successful proposal was made to the Tri-service board for
funding a launch through the Space Test Program. The DOE
then blessed us with support for purchasing a satellite bus,
so we wrote a purchase request for "one satellite each".
Aero-Astro won the bid for the contract and we then found
ourselves in the position of being the integrating contrac-
tor and operator of a small satellite. This patch-quilt sup-
port for the project is why I often call ALEXIS the "Stone
Soup" satellite. It has been made possible by the support of
a lot of different organizations and interests.
July 29, 1991
end...
|
| 745.2 | Newsletter # 2 | TUCKER::BIRO | | Mon Aug 26 1991 14:09 | 127 |
| ALEXIS E-mail Newsletter # 2.
Items of Interest
-----------------
By now, most of you have probably received the NASA Research
Announcement for the Astrophysics Data Program (ADP). It describes the
opportunity to do collaborative guest investigator research with
ALEXIS. See the ADP Research Announcement for details. The writeup
directs questions to Tim Carone, ([email protected] (Inter-
net)), at Berkeley but Bill Priedhorsky ([email protected] (In-
ternet), ESSDP1::087799 (SPAN)) and I ([email protected] or
[email protected] (Internet), ESSDP1::103283 (SPAN)), can also
answer questions about the ALEXIS project.
In some disturbing news, Orbital Sciences Corp., the Pegasus
folks, had a major failure of a sounding rocket at Wallops Island
within the last few days, and the grape vine says all the Pegasus en-
gineers were sent out to Wallops to help resolve the difficulties,
i.e. nobody currently is working on Pegasus and it's problems. The re-
view board for the anomalies seen in the last launch is due to report
in September. The Air Force Space Test Program is currently negotiat-
ing a contractual window for ALEXIS' launch that starts Novemeber 22
and lasts 60 days.
Current Status
--------------
The ALEXIS satellite sitting assembled in a clean room at
LANL, undergoing integrated system tests. Our goal is to complete 3
successfull Functional Integrated System Tests or FISTs before going
to final vibration and environmental tests prior to delivery. An at-
tempt at the first FIST last week failed. The spacecraft did not ap-
pear to "wake up" properly and deploy the solar paddles under simulat-
ed flight conditions. Also, there was a problem with the telescope
high voltage power supplies.
The good news is that yesterday (8/24) we performed the wake
up test sucessfully. For this test, The magnetometer signal input is
replaced by a simulator which provides input to the spacecraft as if
it was spinning or tumbling in a variety of orientations. TV camera
lights are used to fool the spacecraft coarse sun sensors into believ-
ing the satellite was correctly oriented away from the sun. A real
magnetometer was used to observe the spacecraft's magnetic torque
coils' attempts to spin up, down or orient the spacecraft's spin axis
in the correct direction. When the spacecraft correctly thought it was
in the proper orientation, it autonomously deployed it's solar paddles
and started listening for the ground station. An RF link was esta-
blished with the ground station in the adjoining room shortly
thereafter. This was truly a major milestone in the project.
Now for the moderately bad news. It was discovered yesterday
that the real spacecraft magnetometer is acting very flakey. It is on
a plane at this very moment back to the east coast along with an
August 25, 1991
- 2 -
Aero-Astro engineer who will take it to its manufacturer to see what
the trouble is. Also, the HV supply instabilities are at the moment
somewhat of a mystery but several tests and approaches are being made
in parallel. The original engineer who designed the supplies at San-
dia, along with another analog expert from LANL as well as another ex-
pert from Aerospace Corp. are all looking at the problem. At best,
these problems could mean a delay of a week or two to our own tight
schedule which had projected a launch in the late November/early De-
cember time period.
August 25, 1991
|
| 745.3 | Status | TUCKER::BIRO | | Fri Dec 13 1991 07:28 | 6 |
| ALEXIS is completed and waiting launch,
it is expected to be launch now in late Feb or
early March.
jb
|
| 745.4 | update | TUCKER::BIRO | | Wed Jun 17 1992 08:44 | 63 |
|
ALEXIS E-mail Newsletter # 4.
Launch Draws Near
-----------------
It has been over six months since the last ALEXIS newsletter. This has
been partly due to the rate of change and uncertainty of our launch
date. However, it now appears that we are near the end of the road.
The current No-Earlier-Than launch opportunity is July 28.
Current Status
--------------
The ALEXIS satellite passed all of its environmental tests in January.
Since then the satellite has gone through several system integration
tests and six mission simulations where we operated the satellite as
if it were already on orbit. During these tests we detected and
corrected several anomalies associated with the housekeeping electron-
ics on the spacecraft and telemetry system. The last major hurdle is a
mass properties and spin balance adjustment which will be performed at
the end of June at Sandia-Livermore, just prior to shipment to Edwards
Air Force Base for integration with the Pegasus Launch Vehicle.
Orbital Sciences Corp., DARPA, and the Air Force Space Test Program
performed a fairing separation test in Feburary. The test raised some
questions relating to payload contaimination and fairing reliabilty. A
second test is now underway in a vacuum facility at White Sands to
confirm design changes addressing these concerns. There have also been
a series of tests to confirm a design change to improve the reliabilty
of the stage 1-2 separation mechanism.
The ALEXIS experiment has operated sucessfully through all of the re-
cent mission simulations. We have collected over 2 gigabytes of cali-
bration data for the telescopes, the analysis of which is still under-
way. In January we switched out detectors on a 66eV telescope which
points approximately 45 degrees to the anti-sun orientated spacecraft
spin axis. This improved detector resulted in a factor of 5 increase
in throughput for that telescope. The on-axis effective collecting
area at the center of the bandpass for all telescopes ranges from 0.1
to 0.25 cm^2. The telescopes have bandpasses centered at either 66,
71, or 93 eV. The bandpasses, as determined by the structure of the
multilayer mirrors, have widths of approximately 5%. Each telescope
has a field of view of ~33 degrees, with a spatial resolution of ~0.5
degrees.
Recently we obtained the ROSAT Wide Field Camera source list and used
it as input to one of our end-to-end experiment simulations. We scaled
all the source intensities by the count rate ALEXIS should see for the
source HZ43. We discoverd that the brightest 10 or so sources in the
WFC source list should be detectable by ALEXIS in a 12 hour observa-
tion period. We hope to last a year or more.
June 16, 1992
|
| 745.5 | Newsletter # 5 | TUCKER::BIRO | | Mon Jul 06 1992 09:34 | 65 |
|
ALEXIS E-mail Newsletter # 5.
Launch Tip-Toes Away Again
--------------------------
In the last newsletter, I reported that the current No-Earlier-Than
launch opportunity was July 28. Due to some new problems with the
Pegasus launch vehicle, this date now appears unlikely.
Current Status
--------------
On tuesday, June 23 at 8:30AM, ALEXIS left Los Alamos for what was
thought to be the last time. It was on its way to Sandia-Livermore for
final mass properties measurements before delivery to Edwards AFB just
before or after the fourth of July weekend. Early in the morning of
Wednesday, June 24, the vacuum separation test for the Pegasus fairing
failed at White Sands. One half of the fairing was left hanging 10 de-
grees from the vertical to everyone's astonishment. It is now be-
lieved that this failure is probably related to anomalies seen on the
first two flights. A re-test will be manditory and they can't get the
facility back for 30 days. Another issue arose after inspection of
the 1989 pre-flight 1 static ground test article for the stage 1 rock-
et motor. It was found that 300 degrees of the 360 degrees of thread
holding the nozzle in place had been damaged by wear or vibration. A
final resolution and response to this data won't be known until at
least July 8. There is some good news however, the stage 1-2 separa-
tion test went very well and that anomaly seems to have been put to
bed.
Given this situation, ALEXIS is now on it's way back to Los Alamos for
what we hope will be a short storage period instead of going to the
launch site. A new launch date is not known at this time.
July 4, 1992
|
| 745.6 | Newsletter #6 | ECADSR::BIRO | | Mon Nov 16 1992 07:35 | 36 |
|
ALEXIS E-mail Newsletter # 6.
Launch Tip-Toes Towards Us Again!
---------------------------------
In the last newsletter, I reported that the July 28, 1992 launch date
slipped due to some problems with the Pegasus launch vehicle. A new
Launch date around the first week in February (1993) appears extremely
likely. Things to watch for are as follows. There is going to be
another launch of Pegasus before the ALEXIS launch. It will be a
launch from the East coast of a Brazillian satellite sometime in mid-
December. Currently, there is another round of tests occuring at White
Sands of the modified Pegasus fairing design. If this test and the
Brazillian launch, (which uses the new modified first stage rocket
nozzle, but the old fairing), are successful, nothing stands in the
way of an ALEXIS launch in early February.
Current Status
--------------
The ALEXIS satellite is still sitting in its clean room at Los Alamos.
It has just passed a successful Fully Integrated Systems Test (FIST)
and the project is in a mothball mode. Given an early February launch,
the project effort will ramp up right after the New Year with another
FIST and 2 mission simulations in which we operate the satellite from
the ground station as if it was already on orbit. We will then ship to
Edwards for integration with the vehicle approximately 3 weeks prior
to launch.
|
| 745.7 | any news yet | ECADSR::BIRO | | Tue Feb 09 1993 08:00 | 63 |
|
ALEXIS E-mail Newsletter # 6.
Hot News Flash!
---------------
After many delays, Pegasus will finally launch the Brazilians tomor-
row morning (2/9) at 8:15AM EST (5:15AM PST). The launch had been de-
layed from the date reported in my last newsletter due to a problem
with the rudder comming loose during transport on the B-52 from the
west to the east coast, as well as a problem with the Pegasus flight
computer. The launch, as far as we know, is being carried live on NASA
select.
Fairing Test Successful!!
--------------------------
Last Friday, the modified Pegasus fairing design,
to be used for the ALEXIS launch passed the "hot gas" test at White
Sands. This test took place in a large vacuum chamber with the full
operation of all the pyrotechnics required to separate the fairing.
Almost all the actuation is now done electrically, (before many pyros
were actuated by sealed primer cord), and the contamination problems
have all been resolved. Apparently, only two items on the fairing
have not been modified since flight 2 of Pegasus.
Current Status
--------------
With the successful fairing test, and a hopefully successful launch of
the Brazilian satellite tomorrow, nothing stands in the way of an
ALEXIS launch. Upon a successful outcome tomorrow, the ALEXIS project
comes out of "mothball" mode and will be preparing for a launch in
early April.
Disclaimer
----------
This newsletter expresses the opinions of the author and does not re-
flect the official positions of LANL, DOE, or the Space Test Program.
February 8, 1993
|
| 745.8 | #8 | ECADSR::BIRO | | Tue Feb 09 1993 12:34 | 61 |
|
ALEXIS E-mail Newsletter # 8.
Hotter News Flash!
------------------
At approximately 9:30AM EST this morning, Pegasus successfully
launched the Brazilian Communication satellite. This was carried live
on NASA Select. Launch appeared nominal but we are awaiting official
word.
Current Status
--------------
With the successful fairing test, and the successful launch of the
Brazilian satellite this morning, nothing stands in the way of an
ALEXIS launch. We expect the official word from STP on Thursday for
the ALEXIS project to come out of "mothball" mode and prepare for a
launch in early April.
Disclaimer
----------
This newsletter expresses the opinions of the author and does not re-
flect the official positions of LANL, DOE, or the Space Test Program.
February 9, 1993
|
| 745.9 | ALEXIS Newsletter #9 | ECADSR::BIRO | | Wed Apr 07 1993 12:54 | 61 |
|
ALEXIS E-mail Newsletter # 9.
ALEXIS Nears Launch! (Really!)
------------------------------
With the successful launch of Brazilsat, ALEXIS came out of mothball
mode and is now preparing to ship to Edwards Air Force Base in Cali-
fornia for an expected April 25 launch.
Current Status
--------------
In mid-march the ALEXIS project held a "delta" flight readiness review
in front of an external advisory panel. With a few suggestions for im-
provement, they pronounced us ready for launch. One of their recommen-
dations was that we perform a mission simulation in which there are
several "planned" anomalies that the ops team have to work out and did
not know of in advance. This was accomplished last week and included
several "unplanned" anomalies which fortunately turned out to be in
ground test, rather than flight equipment. Tommorow packing begins
for the trip out to California with an expected arrival at the launch
site Sunday evening.
Disclaimer
----------
This newsletter expresses the opinions of the author and does not re-
flect the official positions of LANL, DOE, or the Space Test Program.
April 6, 1993
|
| 745.10 | news letter # 10 | ECADSR::BIRO | | Wed Apr 21 1993 08:42 | 71 |
| From: DECWRL::"[email protected]" "Jeff Bloch" 19-APR-1993 11:45:33.45
To: [email protected]
CC:
Subj:
ALEXIS E-mail Newsletter # 10.
ALEXIS at Dryden Orbital Sciences Facility
-------------------------------------------
I am writing this from the payload trailer at Orbital Science's
Pegasus facility at NASA/Dryden. ALEXIS sits next to the Pegasus rock-
et (which is really neat I might add). Except for a delicate dance
with the Shuttle launch schedule, things seem to be on track for an
April 25 launch.
Disclaimer
----------
This newsletter expresses the opinions of the author and does not re-
flect the official positions of LANL, DOE, or the Space Test Program.
April 18, 1993
|
| 745.11 | Technical problems | ECADSR::BIRO | | Tue Apr 27 1993 08:48 | 75 |
| Subj:
The following is a press release that was distributed this
afternoon. We are heartbroken, but still fighting. I can
answer more technical questions as time permits.
Regards to All,
Jeff Bloch
------------------------------------------------------------------
An Equal Opportunity Employer/Operated by University of California
Los Alamos
NATIONAL LABORATORY
Los Alamos, New Mexico 87545
public information group
news release
CONTACT: John R. Gustafson, (505) 667-7000
draft
ALEXIS SATELLITE SUFFERS MECHANICAL FAILURE DURING LAUNCH
LOS ALAMOS, N.M., April 26, 1993 - Los Alamos National Laboratory
officials today announced that they have so far been unable to establish
radio communication with the ALEXIS satellite, launched yesterday into
orbit by a U.S. Air Force Pegasus booster rocket.
Telemetry data acquired during launch indicates that ALEXIS apparently
suffered a mechanical failure associated with one of its four solar
panels.
The satellite is running on battery power and controllers are continuing
attempts to contact ALEXIS when its orbit carries it over Los Alamos.
"There are a lot of sad faces around here right now, but we're still
hopeful that we can establish communication with ALEXIS and, if we're
successful, reach some of our mission goals," said Bill Priedhorsky,
leader of the ALEXIS team.
ALEXIS, or Array of Low-Energy X-ray Imaging Sensors, is a small
research satellite sponsored by the U.S. Department of Energy's Office
of Arms Control and Nonproliferation. The satellite's principal mission
is to demonstrate advanced instrumentation for the detection of weapon
proliferation, using astrophysical and atmospheric sources to test its
X-ray and radio sensors.
Los Alamos had lead responsibility for ALEXIS' development. Other
participants included Sandia National Laboratories, UC Berkeley's Space
Sciences Laboratory, AeroAstro Inc. and Ovonics Inc. The team has
devoted more than four years to the ALEXIS project.
ALEXIS was launched by a Pegasus booster carried aloft by a NASA-
operated B-52 aircraft. Pegasus, built by Orbital Sciences Corp., put
ALEXIS into the proper orbit.
Additional data taken during launch will be available in the coming days
and will help identify what caused the apparent mechanical failure.
"We'll know more about what happened to ALEXIS when we get the full
telemetry from launch," Priedhorsky said.
"The ALEXIS team members have done a great job and should hold their
heads high," said Don Cobb, leader of the Space Sciences Division at Los
Alamos. "There's risk involved anytime you attempt an experiment like
ALEXIS, which extends the envelope for small satellites in cost-
effectiveness, rapid development and instrument sophistication."
The 240-pound satellite carries six wide-field telescopes Q
incorporating advances such as multi-layer coatings on its curved
mirrors to image X-ray light and state-of-the-art detectors Q designed
to survey the sky in three narrow bands of "soft," or low-energy, X-ray
light. ALEXIS carries a second experiment called "Blackbeard" designed
to measure broadband radio signals from lightning and manmade sources
and the effects of Earth's ionosphere on the signals.
Los Alamos National Laboratory is a multidisciplinary research
organization that applies science and technology to problems of national
security ranging from defense to energy research. It is operated by the
University of California for the U.S. Department of Energy.
-30-
|
| 745.12 | More on ALEXIS' Malfunction | PONIL::J_BUTLER | E pur, si muove... | Mon May 10 1993 10:52 | 26 |
| Article 62318 of sci.space:
Path: nntpd2.cxo.dec.com!pa.dec.com!decwrl!elroy.jpl.nasa.gov!nntp-server.caltech.edu!palmer
From: [email protected] (David M. Palmer)
Newsgroups: sci.space
Subject: Pegasus, ALEXIS, trouble
Date: 8 May 1993 02:46:10 GMT
Organization: California Institute of Technology, Pasadena
Lines: 13
Message-ID: <[email protected]>
NNTP-Posting-Host: alumni.caltech.edu
On April 26, a Pegasus launched the ALEXIS X-ray astronomy satellite.
Video from a camera mounted inside the Pegasus second stage showed that
one of Alexis's solar panels had detatched before separation.
That solar panel contained one of the communications antennas
and a magnetometer system used for attitude control.
As of press-time for the latest Aviation Week and Space News issues,
ground controllers have not been able to re-establish contact
with the spacecraft.
--
David M. Palmer [email protected]
[email protected]
|
| 745.13 | Alexis has some life ! | ECADSR::BIRO | | Thu Jun 03 1993 15:35 | 92 |
| Los Alamos
NATIONAL LABORATORY
Los Alamos, New Mexico 87545
public information group
media advisory
CONTACT: John R. Gustafson, (505) 667-7000
ALEXIS SATELLITE SENDS BRIEF MESSAGE FROM SPACE
LOS ALAMOS, N.M., June 3, 1993 Q Los Alamos National
Laboratory scientists yesterday received three brief radio
transmissions from the ALEXIS satellite, which had not been
heard from since its launch on April 25.
The transmissions were only long enough for the ground
control station and the satellite to agree that they were speaking to
each other. The transmissions were cut off before the satellite
controllers could command it to send information about its
power levels, temperature, orientation and other status reports.
"The good news is that this means there is still life in
ALEXIS," said Jeff Bloch, principal investigator for one of
the satellite's experiments. "For ALEXIS to have sent these
signals means that its receiver must be working, since it only talks
to us after it hears the ground station calling; its transmitter
must be working; it must have had adequate power to turn itself on
for some period of time; and its central processing unit, its
electronic brain, is still functioning."
"This team built a tough little satellite," said Don Cobb,
leader of Los Alamos' Space Sciences Division. "ALEXIS
apparently still has some operational capability after being on its own
for more than a month. We're still a long way, though, from
gaining control of the satellite and salvaging what we can of its
mission."
ALEXIS, which stands for Array of Low-Energy X-ray Imaging
Sensors, is a small research satellite designed and built by
a laboratory-industry team led by Los Alamos and sponsored by
the U.S. Department of Energy's Office of Arms Control and
Nonproliferation. The satellite's principal mission is to
demonstrate advanced instrumentation for X-ray imaging and
broad- band radio detection, for possible use in future space
systems to detect weapons proliferation.
ALEXIS was launched on April 25 by a U.S. Air Force Pegasus
booster, built by Orbital Sciences Corp. Video imagery taken
during launch showed that one of ALEXIS' four solar panels left its
stowed position and possibly detached from the satellite body; the
extent of damage to the panel and any collateral damage to the
spacecraft isn't known at this time.
An investigation team being led by Los Alamos and including
representation from the Air Force and Orbital Sciences is
analyzing all available data from the launch to see whether it can
determine the cause of the damage. That investigation will not be
completed for several months.
ALEXIS is controlled through a ground station at Los Alamos
and can only be contacted during the few orbits each day when
it passes over Los Alamos. During a pass Wednesday afternoon,
the ground station received 32 separate information packets
from ALEXIS, an acknowledgement that the satellite heard
the ground station's call. The information
packets indicated the satellite's central processing unit had
been running for 90 minutes prior to the contact.
The ground station received no signal from the satellite on
subsequent passes Wednesday night and Thursday morning.
The ALEXIS team had previously received information from
ground sources that indicated the satellite had deployed its
three other solar panels in orbit (evidence that it had come to
life in orbit and gone about its housekeeping) and that the fourth
panel was still attached. The spacecraft also was in a stable,
spinning configuration. The team considered that the satellite might
not be communicating because its battery power had gotten too low or
the craft itself had gotten too cold.
The team felt there was a slim hope that as the satellite's
orientation to the sun slowly changed due to Earth's orbital
motion, the craft would get more illumination on its solar
panels to charge itself or more direct illumination to warm it
sufficiently to operate.
Los Alamos National Laboratory is a multidisciplinary
research organization that applies science and technology to problems
of national security ranging from defense to energy research. It
is operated by the University of California for the U.S.
Department of Energy.
|
| 745.14 | More from Alexis | CXDOCS::J_BUTLER | E pur, si muove... | Thu Jul 01 1993 18:05 | 77 |
|
LOS ALAMOS NATIONAL LABORATORY
ALEXIS TALKS TO GROUND STATION FOR SECOND TIME
LOS ALAMOS, N.M., July 1, 1993 Q The Los Alamos National Laboratory
team trying to rescue the ALEXIS satellite received a huge boost of
optimism Wednesday when the satellite sent data to the ground station
and responded to commands sent up from the ground.
Wednesday's contact, only the second since ALEXIS was launched on April
25, lasted about five minutes. The satellite automatically began
talking when it heard the ground station calling. Satellite operator
Cindy Little, on seeing the signal from the spacecraft, sent commands
as planned for the craft to speed up its transmission of onboard status
information. The satellite had been operating for an hour previous to
contact, and sent all data accumulated during that time. The
transmissions cut off when ALEXIS' electrical power levels dropped too
low. "This was a significant contact," said ALEXIS Project Leader Bill
Priedhorsky. "The satellite definitely heard us and responded."
Furthermore, Priedhorsky said, the information ALEXIS sent indicates
that important components of the craft are in good condition. "All four
batteries are working and look good, the satellite is at a good
temperature, and we are getting information from all four solar
panels," he said. One solar panel was damaged during ALEXIS' launch.
ALEXIS' signal showed that panel still has electrical connection to the
satellite, but there was no sign of life from the magnetometer attached
to the panel. The magnetometer provides crucial information for
orienting the craft. Priedhorsky said the ALEXIS team has a lot of
data in hand to use in figuring out the satellite's condition and why
there is such a long duration between contacts.
"Step one has always been to establish communication with ALEXIS and
get down the housekeeping data about its status," Priedhorsky said.
"We've done that. Now we have to use that data to understand the state
of the satellite and determine what are the right commands to send it
when we contact it again." With the proper commands, the ALEXIS team
hopes to stabilize the satellite and improve its condition so it can
speak with the ground station more regularly.
If that task is successful, the team can move on to getting the
satellite into the best possible configuration for operations and carry
out as much of the satellite's experimental mission as possible.
ALEXIS, which stands for Array of Low-Energy X-ray Imaging Sensors, is
a small research satellite designed and built by a laboratory-industry
team led by Los Alamos and sponsored by the U.S. Department of
Energy's Office of Intelligence and National Security. The satellite's
principal mission is to demonstrate advanced instrumentation for X-ray
imaging and broad-band radio detection, for possible use in future
space systems to detect weapons proliferation.
ALEXIS was launched on April 25 by a U.S. Air Force Pegasus booster,
built by Orbital Sciences Corp. Video imagery taken during launch
showed that one of ALEXIS' four solar panels left its stowed position,
causing damage whose full extent still is not known.
An investigation team being led by Los Alamos and including
representation from the Air Force and Orbital Sciences is analyzing all
available data from the launch to see whether it can determine the
cause of the damage. That investigation is expected to be completed by
the end of August. ALEXIS is controlled through a ground station at
Los Alamos and can only be contacted during the few orbits each day
when it passes over Los Alamos. On June 2, the ground station received
32 separate information packets from ALEXIS, an acknowledgement that
the satellite heard the ground station's call. The information packets
indicated the satellite's central processing unit had been running for
90 minutes prior to the contact.
That was the only contact with the craft until Wednesday's pass.
Los Alamos National Laboratory is a multidisciplinary research
organization that applies science and technology to problems of
national security ranging from defense to energy research. It is
operated by the University of California for the U.S. Department of
Energy.
|
| 745.15 | latest as of 2 July | ECADSR::BIRO | | Tue Jul 06 1993 11:18 | 29 |
|
Dear Friends of ALEXIS,
In the last two days we have had two successful contacts with the
ALEXIS satellite. That's the good news. The bad news is that we have
lost the magnetometer on the sattelite that was used for magnetic
torquing to control the spacecraft spin and attitude. This makes
useless all of the spacecraft attitude control software and the
ground attitude determination software that currently exists.
We can manually control the magnetic torque coils, as well
as uplink new code into spacecraft RAM. We have functioning coarse
and fine sun sensors as well as a functioning horizon crosssing
indicator. We have daily updates on the spacecraft ephemeris.
We have to come up with a new strategy for attitude control
and determination under the above constraints. We are looking for
tools and expertise that might be able to help us on a short
timescale, as we may only have a few weeks of power to get ourselves
tracking the sun again. Any leads or suggestions would be greatly
appreciated.
Jeff Bloch
(505)665-2568
(505)665-4414 FAX
[email protected]
|
| 745.16 | update | ECADSR::BIRO | | Thu Jul 08 1993 09:39 | 83 |
| :
Subj: ALEXIS - Every way and every day,...Better and Better!
Los Alamos National Laboratory Public Information Group
Los Alamos, New Mexico, 87545 News Release
An Equal Opportunity Employer/Operated by University of California
CONTACT: John R. Gustafson, 505-665-7777
REGULAR CONTACT WITH ALEXIS
LOS ALAMOS, N.M., July 7, 1993 Q The Los Alamos National Laboratory team
responsible for the ALEXIS satellite on Monday successfully commanded the
spacecraft to shut down nonessential systems, reducing the drain on its onboard
batteries, and has since established regular communications with the spacecraft.
"This was a major step toward getting full control over ALEXIS and has the team
really pumped up," said Jeff Bloch, principal investigator and acting leader for
the project. "Most of the onboard systems look really good, which has confirmed
the team's faith that we built a hardy, resourceful little satellite."
ALEXIS had been essentially out of touch since it was launched April 25 by a
U.S. Air Force Pegasus booster, built by Orbital Sciences Corp. One of the
satellite's four solar panels was damaged during launch, which is likely
associated with the communication difficulties.
Brief transmissions from the satellite were received by the Los Alamos ground
station on June 2, June 30 and July 1.
ALEXIS now has been working continuously since the contact on July 5, when the
team radioed up commands to shut down some systems. The power in the batteries,
charged by solar panels, has been inching upward ever since, and will soon reach
levels that will let the team consider other options for gaining full control of
the satellite.
"We feel confident now that we will be able to operate ALEXIS' experiments, at
least at some level, and achieve many of our mission goals," said Don Cobb,
leader of the Space Sciences and Technology Division at Los Alamos.
ALEXIS, which stands for Array of Low-Energy X-ray Imaging Sensors, is a small
research satellite designed and built by a laboratory-industry team led by Los
Alamos and sponsored by the U.S. Department of Energy's Office of Intelligence
and National Security.
The satellite's principal mission is to demonstrate advanced instrumentation for
X-ray imaging and broad-band radio detection, for possible use in future space
systems to detect weapons proliferation.
The instruments also produce valuable scientific data for astrophysics and upper
atmosphere research.
Data sent from ALEXIS indicate that its solar panels are not in a good
orientation relative to the Sun, and thus are not providing maximum charge to
the batteries. ALEXIS had been in a state where it had barely enough power to
turn itself on, then would quickly drain its batteries and shut down again. By
turning off the nonessential systems and letting the satellite rest as much as
possible, the ALEXIS team is allowing the batteries to continue charging.
The satellite's power levels are improving day by day.
The ALEXIS team is also exploring ways to realign the craft so its solar panels
face the Sun more directly. This effort is complicated because the damage
suffered during launch apparently disabled the magnetometer, which the satellite
would normally use to control its orientation. The team has to determine whether
it can manually command the satellite's attitude to swing it around to a better
orientation.
If the ALEXIS team can learn to fly the spacecraft from the ground and charge
the batteries up to a high enough level, it can then turn on the X-ray and radio
experiments. "We still have a lot of hard work ahead of us before we reach that
step, though," Bloch said.
AeroAstro Inc., the company that built the body and guts of the satellite, has
been interacting daily with Los Alamos in the rescue attempt.
Los Alamos National Laboratory is a multidisciplinary research organization that
applies science and technology to problems of national security ranging from
defense to energy research. It is operated by the University of California for
the U.S. Department of Energy.
|
| 745.17 | lastest on ALEXIS | ECADSR::BIRO | | Tue Jul 13 1993 17:15 | 111 |
| From: US1RMC::"[email protected]" "Jeffrey J Bloch" 13-JUL-1993 16:09:12.00
To: [email protected]
CC:
Subj: ALEXIS Performs Science Tasks
Date: 13 Jul 93 14:03:54 EDT
From: "John R. Gustafson" <[email protected]>
To: Jeff Bloch <[email protected]>
Subject: Latest ALEXIS release
Message-Id: <[email protected]>
LOS ALAMOS NATIONAL LABORATORY
CONTACT: John R. Gustafson, (505) 667-7000
ALEXIS SATELLITE CARRIES OUT FIRST EXPERIMENTS
LOS ALAMOS, N.M., July 13, 1993 - The ALEXIS satellite developed by a Los
Alamos National Laboratory team carried out its first scientific experiments
on Sunday and Monday, measuring a wide range of radio emissions from Earth and
looking for a specific radio pulse sent up from the ground.
Not bad for a satellite that reached orbit damaged, didn't talk to the ground
for more than two months and previously had a bleak prognosis.
"This was a significant scientific observation," said Dan Holden, principal
investigator for the Blackbeard radio experiment aboard ALEXIS. "If I were a
gold miner, this would be paydirt."
Blackbeard, one of two scientific instruments aboard the $17 million
satellite, uses a broadband receiver to detect radio signals from Earth,
including bursts of radio energy triggered by lightning, and measure how the
ionosphere - an electrically conducting region in the atmosphere - disperses
and distorts such signals.
Blackbeard's radio receiver can listen to thousands of frequencies
simultaneously and can take 150 million measurements each second. It sees
signals from standard communications carriers and from small sources of radio
noise such as car ignitions and kids' walkie-talkies.
"We're interested in making recordings of the Earth's radio noise at different
times," Holden said. "There have been lots of measurements before at specific
frequencies, but Blackbeard can give us a detailed characterization of the
background at many frequencies at once."
Monday's experiment took place during ALEXIS' 1,119th orbit after launch. The
ALEXIS team plans to attempt additional Blackbeard experiments today.
"We have a window of opportunity," said Blackbeard experimenter Carter Munson.
"ALEXIS has sufficient power right now for limited Blackbeard operations, so
we are eager to get really critical data while we can."
Blackbeard and ALEXIS' other experiment - six telescopes for capturing
low-energy X rays from astrophysical sources - were built to demonstrate
advanced instrumentation for possible use in future space systems to detect
nuclear weapons proliferation. Blackbeard, by measuring the background radio
noise, will provide baseline data useful for separating everyday radio
emissions from the specific signature of a nuclear explosion.
The measurements Blackbeard makes also are useful for engineers developing
space-based communications systems. The data will be used in completing the
design of FORTE, a small satellite now under development at Los Alamos. The
data also will be an important contribution to the scientific literature in
this field.
To measure the ionosphere's effect on radio transmissions, the Blackbeard team
sends a burst of radio energy toward the ALEXIS satellite while Blackbeard is
operating. Comparing the received signal to the transmitted one lets Holden
and his colleagues sort out the effects of the ionosphere. In two attempts so
far, they have not spotted the burst in the Blackbeard data, and they are
refining Blackbeard's operating parameters in hopes of a successful
observation.
Prospects for a successful ALEXIS mission appeared bleak when the satellite
suffered damage during its launch on April 25. One of its four solar panels
was damaged, and ALEXIS gave no signs of life until a brief transmission on
June 2.
Working from a ground station at Los Alamos, the ALEXIS team finally regained
control of the spacecraft on July 5. The team has learned from information
sent by ALEXIS that the satellite is poorly oriented with respect to the Sun
and does not get direct illumination on its solar panels, necessary for
rapidly charging its batteries.
During the July 5 contact, the team commanded ALEXIS to shut off non-essential
systems, and the satellite thereafter was able to charge its batteries fully
on the small amount of sunlight it receives. The craft has been operating
continuously and has had sufficient power to conduct some operations -
including limited Blackbeard observations - since the July 5 contact.
The ALEXIS team is searching for ways to improve the satellite's orientation,
to swing it around so its solar panels face the Sun more directly. The damage
suffered by the satellite, however, apparently disabled an onboard device used
for orienting the craft. The team will have to learn to fly the satellite from
the ground, rather than using the onboard system as designed.
ALEXIS, which stands for Array of Low-Energy X-ray Imaging Sensors, was
designed and built by a laboratory-industry team led by Los Alamos and
sponsored by the U.S. Department of Energy's Office of Intelligence and
National Security.
AeroAstro Inc., the company that built the satellite bus, is interacting daily
with Los Alamos to salvage as much of ALEXIS' mission as possible.
Los Alamos National Laboratory is a multidisciplinary research organization
that applies science and technology to problems of national security ranging
from defense to energy research. It is operated by the University of
California for the U.S. Department of Energy.
-30-
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% Newsgroups: sci.space.news
% Path: ames!dont-send-mail-to-path-lines
% From: [email protected] (Jeffrey J Bloch)
% Subject: ALEXIS Performs Science Tasks
% Message-Id: <[email protected]>
% Followup-To: sci.space
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|
| 745.18 | ALEXIS 1st Light | ECADSR::BIRO | | Wed Jul 28 1993 09:43 | 73 |
| Subj: ALEXIS First Light!
LOS ALAMOS NATIONAL LABORATORY
CONTACT: John R. Gustafson, (505) 667-7000
CompuServe Acct: 71742,1311
"FIRST LIGHT" FOR ALEXIS
LOS ALAMOS, N.M., July 27, 1993 - Los Alamos National Laboratory scientists
early Tuesday morning powered up one of the six X-ray telescopes on the ALEXIS
satellite and operated the novel instrument for the first time in orbit.
The ALEXIS telescopes capture and focus "soft," or low-energy, X-rays. Other
telescopes onboard ALEXIS will be turned on later this week, building toward
all-out astronomical observations with the full suite of telescopes.
"All indications are that the telescope worked beautifully," said Jeff Bloch,
lead scientist for the X-ray telescope experiment. "We adjusted the voltage on
the telescope's detector until we were getting decent count rates for photons
detected and then had about a four-minute exposure at that voltage level.
There is exciting information in this data that we need for running the
telescopes for real astronomical work."
"First light" is a special time for telescopes, but does not represent the
start of regular observations. The ALEXIS team needs to determine the optimum
operating conditions for the telescopes and measure the background radiation
from sources in the near-Earth environment so those effects can be separated
from the astrophysical X-ray emissions of interest.
ALEXIS, which stands for Array of Low-Energy X-ray Imaging Sensors, is Los
Alamos' first full-scale entry into the small satellite field. The $17 million
satellite, sponsored by the U.S. Department of Energy's Office of Intelligence
and National Security, was designed and built by a laboratory-industry team
led by Los Alamos and is operated from a ground station at the Laboratory.
"ALEXIS is first and foremost a technology demonstration mission," said Bill
Priedhorsky, ALEXIS project leader. In addition to the six X-ray telecopes,
ALEXIS carries a broadband radio experiment called Blackbeard, which has been
used successfully in a series of experiments that started July 11.
Both experiments on ALEXIS were built to demonstrate advanced instrumentation
for possible use in future space systems to detect nuclear weapons
proliferation, but "by testing the technology with astrophysical and
atmospheric sources we can conduct valuable scientific studies," Priedhorsky
said.
Data from ALEXIS' X-ray telescopes, for example, will be made available to
researchers through NASA's astrophysical data program.
The coffee-can-sized telescopes, each with a 30-degree-wide view of the sky,
use recently developed multilayered coatings on their curved mirrors to
reflect and focus X-rays much the way that optical telescopes focus visible
light. ALEXIS' telescopes will monitor the entire sky in three separate
low-energy X-ray windows: 62 electron-Volts, 72 eV and 93 eV, respectively. A
typical medical X-ray, by comparison, has an energy of 80,000 eV.
The telescopes' combination of wide-field view and precise energy resolution
offer a unique view of the cosmos that complements information being returned
by other orbiting observatories.
The detectors on the X-ray telescopes were built by the Space Sciences
Laboratory at the University of California, Berkeley. The detectors have to
time precisely the arrival of each X-ray photon so researchers can determine
where the spinning satellite was pointing when the photon arrived. The ALEXIS
team will need to "despin" the data to reconstruct an unblurred picture of the
sky, a task complicated because damage ALEXIS suffered during launch requires
that the computer programs to reconstruct the X-ray images be rewritten from
scratch.
ALEXIS was launched April 25 on a U.S. Air Force Pegasus booster built by
Orbital Sciences Corp. One of the satellite's solar panels was damaged during
the launch phase and the satellite was not brought under control until July 5.
The ALEXIS team is still learning how to compensate for the damage to the
satellite in advancing to full-scale operations.
Los Alamos National Laboratory is a multidisciplinary research organization
that applies science and technology to problems of national security ranging
from defense to energy research. It is operated by the University of
California for the U.S. Department of Energy.
-30-
|
| 745.19 | | SKYLAB::FISHER | Carp Diem : Fish the Day | Wed Jul 28 1993 13:42 | 5 |
| Wow that's wonderful! What a great success story!
I wonder how they are managing to stabilize without the magnetometer?
Burns
|
| 745.20 | | ECADSR::BIRO | | Thu Sep 09 1993 14:18 | 89 |
|
LOS ALAMOS NATIONAL LABORATORY
Contact: John Gustafson
LANL Public Affairs Office
(505)667-7000
ALEXIS OPERATES SIX X-RAY EYES AT ONCE
LOS ALAMOS, N.M., Sept. 9, 1993 - The ALEXIS satellite took a major step on
its recovery this week when for the first time it operated all six of its
X-ray telescopes and its radio-frequency experiment simultaneously, Los Alamos
National Laboratory officials said today.
"ALEXIS for the first time has demonstrated that it can deliver useful data
from all of its onboard experiments," said Jeff Bloch, principal investigator
for the X-ray telescopes. "If we can make the next leap to where this becomes
a routine operation then we'll be well on our way to having a fully
operational satellite capable of completing its mission goals."
The $17 million ALEXIS satellite, sponsored by the Department of Energy's
Office of Intelligence and National Security, was built by a
laboratory-industry team led by Los Alamos. Other team members include Sandia
National Laboratories, the University of California at Berkeley, AeroAstro
Corp. and Ovonics Inc.
Launched April 25, the satellite reached orbit damaged and initially appeared
lost. In fits and starts, the ALEXIS team has brought the satellite back to a
condition where it can perform nearly all of its original functions, despite a
damaged solar panel and a misaligned spin.
The coffee-can-sized X-ray telescopes, each with a 30-degree-wide view of the
sky, use recently developed multilayered coatings on their curved mirrors to
reflect and focus low-energy X-rays much the way that optical telescopes focus
visible light. The telescopes' combination of wide-field view and precise
energy resolution offer a unique view of the cosmos that complements
information being returned by other orbiting observatories.
Because the satellite spins, the arrival of each X-ray photon has to be
carefully timed so scientists know precisely where the telescope was pointing
when the photon arrived. The data have to be "despun" before they can be used
to reconstruct a picture of the sky, a task complicated by the satellite's
off-axis, wobbling spin.
"It's going to be several months before we have an accurate enough
characterization of the satellite's spin to decipher the X-ray data with
confidence," Bloch said.
The radio frequency experiment, called Blackbeard, uses a broadband receiver
to detect radio signals from Earth, including bursts of radio energy triggered
by lightning, and measure how the ionosphere - an electrically conducting
region in the atmosphere - disperses and distorts such signals. Blackbeard's
receiver can listen to thousands of frequencies at once and can take 150
million measurements each second; it has been used routinely since mid-July.
The novel X-ray and radio technologies are being evaluated for possible
application in future space-based systems for detecting weapons proliferation.
At the same time, data from the experiments are being provided to the research
community at large. Data from the X-ray telescopes will be made available
through NASA's astrophysical data program, and arrangements are being made to
distribute the Blackbeard data through similar means.
The ALEXIS team spent a tense two weeks in August when the satellite fell
silent. Team members believe the problem was connected with the temperature of
the satellite; when it gets too warm - as it did during the two weeks when it
was constantly illuminated by the sun - the onboard communications receiver
apparently becomes disabled and ALEXIS cannot hear the ground station calling
it to attention.
By carefully monitoring the temperature of ALEXIS and preventing it from
getting too warm, the satellite team hopes to avoid future communication
lapses.
In addition, the ALEXIS team recently transmitted new software commands to
prevent the satellite's computers from being tripped, or reset. Roughly once a
day, one of the satellite's four data-processing units for the experiments
would be tripped as the satellite crossed the South Atlantic Anomaly, a region
above the South Atlantic where satellites encounter a swarm of trapped charged
particles. The extra radiation can play havoc with electronics.
Early indications are that the new software is doing the job.
In the meantime, the data continue to accumulate, radioed by ALEXIS to a
ground station at Los Alamos during the few orbits each day when the satellite
passes overhead.
"We are still optimizing the operating characteristics of the telescopes, but
portions of the data already acquired look like they will be of sufficiently
good quality for us to extract any signals coming from celestial sources,"
Bloch said.
Bloch said the X-ray observations are complicated by high numbers of
background photons generated by particles trapped in Earth's magnetosphere or
sunlight reflected from the atmosphere back to the satellite.
New software being written by collaborators at Sandia will throttle down the
voltage to the telescope detectors when the background counts grow too high,
thus increasing the amount of useful astrophysical data from the telescopes.
Los Alamos National Laboratory is a multidisciplinary research organization
that applies science and technology to problems of national security ranging
from defense to energy research. It is operated by the University of
California for the U.S. Department of Energy.
|
| 745.21 | msg # 10 | ECADSR::BIRO | | Thu Dec 23 1993 08:35 | 260 |
| ALEXIS Telescope E-mail Newsletter # 10.
HAPPY HOLIDAYS TO ALL FROM TEAM ALEXIS!
(Los Alamos, Sandia, UCB-SSL, and AeroAstro)
It has been several months since the last ALEXIS e-mail newsletter so
it is time to fill in the void. For those of you getting this for the
first time, this series of newsletters is sent to those in the astro-
physics community that have expressed an interest in the progress of
the ALEXIS project.
With this newsletter, we are also posting to the internal LANL usenet
newsgroup lanl.nis.alexis. The amount and type of traffic on this
newsgroup will be an evolving experiment over the next few months.
The alexis_newsletter exploder now also includes the projldrs ex-
ploder, as well as the nis-council exploder.
ALEXIS Spacecraft Status
------------------------
Except for a two week loss of contact in August, (see below), we have
been successfully operating the ALEXIS spacecraft since we recovered
it in late June (June seems a 1,000 years ago!).
No degradation in spacecraft performance has been detected since the
start of operations. That is not to say that we have not uncovered
problems as we "explored" the operational parameter space of the dam-
aged spacecraft. As you recall, one of the four solar paddles on the
satellite broke off from it's mounting points during launch on April
25. The panel is still attached to the satellite by a guy wire and the
power, rf, and signal cable bundle, but it appears to be about a foot
further away from the spacecraft body than it was supposed to be. The
spacecraft is still getting power and probably the use of the
telemetry antenna on the end of the paddle. However, the one and only
spacecraft magnetometer was located on the broken paddle and is dead.
Electrically, it is the only thing that has failed on the spacecraft.
I will list below the major problems that we have encountered to date
and their resolutions:
1. No Magnetometer: ALEXIS is a spin stabilized, Sun oriented,
satellite. It was originally designed to autonomously place the spin
axis of the spacecraft on the Sun line using magnetic torque coils
controlled by the on-board software. For this scheme to work, the
spacecraft needed to know where the local magnetic field pointed. With
the magnetometer broken, the "closed loop control system" now goes
through the operations team on the ground. In order to point the spin
axis near the Sun, we have to do a procedure called "Quarter Orbit
Torqueing". We send the spacecraft timed commands to turn on and off
the torque coils that are aligned with the spin axis in such a manner
that the resulting precession moves the spin axis towards the Sun.
This procedure involves determining where the spin axis is pointed
(not an easy thing at first), and then computing the magnetic field
December 22, 1993
- 2 -
orientation as a function of orbit position in order to compute the
optimum times to activate the coils. So like a tacking sailboat,
every few days we nudge the spacecraft's spin axis back in the right
direction. This is important because gravity gradient torques and
residual magnetic torques can cause the spacecraft spin axis to move
up to 6 degrees a day, although at times the motion is much less than
a degree. We also have devised a method for spinning up the space-
craft without a magnetometer. The spin period increases by about 0.1
seconds per day, and if the spin rate becomes too low, one of the
remaining attitude determination tools, the horizon crossing indica-
tor, does not function correctly. To spin the spacecraft up, we loaded
a new piece of software into spacecraft RAM that when running, turns
on and off the torque coils perpendicular to the spacecraft spin axis
based on whether the horizon crossing indicator is looking at the
earth or not. This code is then enabled for the parts of the orbit
that are computed to cause a net increase in spin rate for that phas-
ing function.
2. Changed Mass Properties: Because of the broken solar pad-
dle, the major principle axis of the spacecraft is tilted about 15 de-
grees where it was intended to be. This misalignment causes a signi-
ficant change in the way that the telescopes scan the sky during a
spacecraft rotation. Detailed analysis of the sun sensor data indi-
cates that the new principle axis is stable in the spacecraft body
coordinate system and that we should be able to make a good determina-
tion of the new mass properties.
3. Spacecraft stops communicating when it gets too hot: The
two week loss of contact with the satellite in August was caused by
portions of the spacecraft getting too warm. For that two week period,
the spacecraft entered a 100% sunlight orbit. It appears that part of
the solar blanket surrounding the analog receiver circuits on the out-
side of the spacecraft electronics box was probably pulled back like a
skirt when the solar paddle was damaged. This is surmised from a ther-
mal analysis that indicates that the bottom of the spacecraft is re-
ceiving approximately 15 to 20 watts of excess heating that is other-
wise unaccounted for. Since the inside of the blanket is shiny, the
blanket maybe focusing sunlight on the electronics it was originally
supposed to protect. In October, during another period of 100% solar
illumination time, we did not lose contact as we shut down every sys-
tem we could to cool the spacecraft. This reduced the temperature
enough to stay in contact continuously. We now believe that in the
100% sunlight condition, that we have enough thermal margin to run the
experiments at a level that is 10%-15% of the normal duty cycles.
Periods of 100% illumination occur on alternating 1.5 and 3 month cy-
cles due to our 70 degree inclination orbit and the seasonal changes
of the Sun's position on the sky.
4. Inoperable Attitude Solution Algorithms: In order to
achieve full scientific return from the EUV/Ultrasoft x-ray tele-
scopes, we need to know the attitude of the satellite to a precision
of 0.2 degrees, matching the telescope point response functions. The
original software to do this was invalidated by the loss of the magne-
December 22, 1993
- 3 -
tometer and the altered mass properties of the satellite. Efforts are
in full swing to come up with alternative software using the HCI and
Sun sensors alone. Analysis of the problem so far shows that it is
solvable, but that the spacecraft nutates or "wobbles" significantly
from time to time. The wobble has to be taken into account to achieve
the sub-one degree determination required. The nutation amplitude has
varied over the past few months from 0.2 degrees to 3 degrees. The
period of this nutation is approximately 430 seconds, compared to the
spin period of approximately 46 seconds. With the loss of the magne-
tometer, we also lost the on-board system that was to actively dampen
these nutations.
ALEXIS Telescope Status
-----------------------
The attitude determination problem has not prevented us from running
the telescopes. The data is archived and when a determination tool
comes on line, all the telescope data going back to July can be used
to make maps of the sky.
All six ALEXIS telescopes are now in operation. There have been
periods in the last month or two that 1 to 3 telescopes have not been
operating due to microchannel plate detector instability. We believe
that these conditions were caused by extended operations of the detec-
tors in high particle flux regions that caused the surfaces of the mi-
crochannel plates to release residual amounts of trapped gas. Pro-
cedures that operated these detectors at reduced gains over periods of
days or weeks with gradual increases in the operating voltages were
successful in bringing them back on line.
On each orbit, the ALEXIS telescopes are collecting low count rate
data from the sky for approximately 5 to 15 minutes depending on the
orbit geometry and the relative positions of the South Atlantic Anoma-
ly and Auroral zones.
Despite Problems, ALEXIS Sees First Point Source!
-------------------------------------------------
Despite the problems determining spacecraft attitude, a few crude
tools have been put together to "de-spin" the photon data onto a fake
coordinate system that has as its poles the spacecraft spin axis. This
method works if a) the spin vector stays fixed inertially (WRONG- the
spin axis can move up to 6 degrees a day on the sky), and b) the
spacecraft spin rate stays constant (WRONG - the spacraft spin period
does slow down due to eddy currents, about 0.1 seconds/day, and nuta-
tion causes a periodic change in the effective spin period as viewed
by an observer on the spacecraft watching a fixed point in inertial
space.)
Anyway, during the week of December 1 we were lucky! The spacecraft
nutation was small (~0.2 degrees), and the orbital configuration was
December 22, 1993
- 4 -
such that the drift rates were small (~0.2 degrees/day). This made our
crude tools work well and as good fortune would have it, the full Moon
was in the field of view of our spin-axis looking telescopes and
popped out as a 10 sigma detection. (Three cheers for science team
member Diane Roussel-Dupre' who made the discovery!) Analysis underway
to determine how much of the flux is in our bandpass or in a possible
UV light leak since the Moon is very bright at many wavelengths. The
moon was observed for several days. It disappeared from the crudely
produced images when the nutation amplitude again increased to about 2
degrees.
(Remember- Each ALEXIS telescope has a 33 degree field of view, with a
FWHM point response function of 0.2 degrees. Therefore the Moon, an
extended source to most astronomers, is practically a point source for
us.)
This data set will be very important for testing new attitude determi-
nation algorithms as they are developed.
Searches continue for other bright point sources that we expect to be
able to see with our current analysis techniques.
Visit Our AAS Poster
--------------------
We will be presenting a poster titled "The ALEXIS Project: EUV Astro-
physics on a Rollercoaster", describing the current status of the pro-
ject at the upcomming American Astronomical Society Meeting in Wash-
ington D.C. (Poster 113.10, Saturday, January 15).
Know of a Good Postdoc??
------------------------
We are in the process of seeking a Postdoc to help analyze the ALEXIS
data. If anyone knows of someone with experience analyzing EUV or X-
ray satellite or sounding rocket experiments or has equivalent in-
terests, please contact me at the address below.
Disclaimer
----------
This newsletter expresses the opinions of the author and does not re-
flect the official positions of LANL, DOE, or the Space Test Program.
--------------------------------------------------------------------------
Jeffrey Bloch Office: (505) 665-2568
Astrophysics and Radiation Measurements Group ALEXIS Soc: (505) 665-5975
Los Alamos National Laboratory FAX: (505) 665-4414
Mail Stop D436 e-mail: [email protected]
Los Alamos, NM 87545
**** Goodbye SST-9 ---> Hello NIS-2 (A rose by any other name????)*******
--------------------------------------------------------------------------
December 22, 1993
7
|
| 745.22 | ALEXIS makes first celestial images | MTWAIN::KLAES | Keep Looking Up | Tue May 17 1994 23:05 | 119 |
| From: US4RMC::"[email protected]" "Jeff Bloch" 17-MAY-1994 20:01:15.95
To: [email protected]
CC:
Subj: ALEXIS NEWSRELEASE - ALEXIS Detects HZ43
The following is the text of a press release distributed today. If anyone
would like a color postscript version of the image mentioned in the text,
please e-mail me and I will e-mail back to you a copy. I'm working on an
anonymous ftp way of distributing this image, but it is not on line yet.
--------------------------------------------------------------------------
Jeffrey Bloch Office: (505) 665-2568
Astrophysics and Radiation Measurements Group ALEXIS Soc: (505) 665-5975
Los Alamos National Laboratory FAX: (505) 665-4414
Group NIS-2, Mail Stop D436 e-mail: [email protected]
Los Alamos, NM 87545
--------------------------------------------------------------------------
ALEXIS TEAM RELEASES FIRST CELESTIAL IMAGE
LOS ALAMOS, N.M., May 17, 1994 - Scientists have produced the first
celestial image of a star from X-ray data gathered by Los Alamos National
Laboratory's ALEXIS satellite. The achievement is a significant step toward
creating a Rosetta Stone for decoding the mountain of celestial data ALEXIS
has radioed to Earth in the year since its launch.
The spin-stabilized satellite, launched April 25, 1993, has a significant
wobble due to a damaged solar panel. The damage also left ALEXIS unable to
provide precise information about its orientation as it was originally
designed. The ALEXIS team had to find a new way to determine where any of
the satellite's six X-ray telescopes points at any given moment - essential
for reconstructing an image of the sky.
To create the celestial image, the ALEXIS team used a computer program
developed by AeroAstro, Inc., that defines the satellite's moment-by-moment
orientation. (AeroAstro also built the satellite's central unit and onboard
support systems for power, attitude control and telemetry.) With the
satellite's orientation sufficiently well defined, the team could begin
processing the telescope data.
The image shows a broad slice of the X-ray sky with two bright sources
clearly visible: the Moon and the white dwarf HZ 43, the hot remnant of a
star near the end of its life.
"HZ 43 is the brightest stellar source of soft X rays in the sky, so it's a
good marker for testing the computer code developed to reconstruct the
satellite's orientation," said ALEXIS Project Leader Jeff Bloch. The next
step, Bloch said, is to use the directional information provided by HZ 43 to
refine the computer code and improve its accuracy. After that, the code will
be moved onto a faster machine so the team can begin processing more of the
nine months of archived data.
-more-
ALEXIS' FIRST PICTURE
PAGE 2:
The observation also is significant, Bloch said, because "the performance of
the instrument is right on the estimates we made based on pre-flight
calibrations. This means that after a year of exposure to the space
environment there has been no serious degradation of the telescope -
mirrors, detectors, filters, it all has to work right."
In the image, the Moon left a short streak as it moved over the 12-hour
exposure. The doughnut-shaped sky image shows the scan path of the telescope
as the satellite rotates. Bloch and his colleagues are still examining other
textures in the image to determine if they are real celestial emissions or
instrumental and data-processing artifacts.
ALEXIS' X-ray telescopes feature curved mirrors whose multilayer coatings
reflect and focus low-energy X rays the way optical telescopes focus visible
light. The detectors that record the arrival of X-ray photons were built by
a team at the University of California, Berkeley.
The wide-field telescopes - each has a 30-degree field of view - provide new
capabilities for celestial observations, complementary to other missions
currently operating such as NASA's Extreme Ultraviolet Explorer and the
NASA-European Space Agency X-ray satellite called Rosat. When ALEXIS data is
fully decoded, the satellite will provide a unique sky map for studying
celestial emissions of soft X rays.
Already the ALEXIS team has on hand more than 25 compact disks full of data,
each holding 650 megabytes of information (equaling in total more than two
million pages of written text, approximately). About 60 percent of this
information is telescope data; the rest is satellite operational data and
observations from Blackbeard, a broadband radio receiver that records both
manmade and natural radio emissions from Earth.
ALEXIS, which stands for Array of Low-Energy X-ray Imaging Sensors, was
funded by the Department of Energy's Office of Intelligence and National
Security. The $17 million satellite was launched on a U.S. Air Force Pegasus
rocket built by Orbital Sciences Corp.
-more-
ALEXIS' FIRST PICTURE
PAGE 3:
Because of the initial damage to ALEXIS, the team could not contact the
satellite for the first six weeks after launch, causing them to fear it was
lost. After making contact, the team was able to assess the onboard damage
and develop alternate procedures for controlling the satellite and its
experiments. ALEXIS has been restored to near-normal operations and both
onboard payloads are returning valuable scientific data.
Los Alamos oversaw the satellite's development and built the X-ray telescope
and Blackbeard payloads. The satellite is controlled from a small ground
station at Los Alamos.
Los Alamos National Laboratory is a multidisciplinary research organization
that applies science and technology to problems of national security ranging
from defense to energy research. It is operated by the University of
California for the U.S. Department of Energy.
-30-
% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% Date: Tue, 17 May 1994 17:50:11 -0600 (MDT)
% From: Jeff Bloch <[email protected]>
% Subject: ALEXIS NEWSRELEASE - ALEXIS Detects HZ43
% To: [email protected]
|
| 745.23 | FTP site available | MTWAIN::KLAES | Keep Looking Up | Wed May 18 1994 14:24 | 31 |
| From: US4RMC::"[email protected]" "Jeff Bloch" 18-MAY-1994 13:14:08.22
To: "Riegler, Guenter" <[email protected]>
CC: [email protected]
Subj: ALEXIS NEWSRELEASE - FTP Instructions for postscript images
The ftp setup is now on line. Ftp anonymous to sst.lanl.gov,
Then cd to pub/alexis
There are four files there:
release.txt == press releases
captions.txt == figure captions
figure1.ps == color postscript unlabeled image
figure2.ps == color postscript labeled image
--------------------------------------------------------------------------
Jeffrey Bloch Office: (505) 665-2568
Astrophysics and Radiation Measurements Group ALEXIS Soc: (505) 665-5975
Los Alamos National Laboratory FAX: (505) 665-4414
Group NIS-2, Mail Stop D436 e-mail: [email protected]
Los Alamos, NM 87545
--------------------------------------------------------------------------
% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% Date: Wed, 18 May 1994 10:59:36 -0600 (MDT)
% From: Jeff Bloch <[email protected]>
% Subject: ALEXIS NEWSRELEASE - FTP Instructions for postscript images
% To: "Riegler, Guenter" <[email protected]>
% Cc: [email protected]
|
| 745.24 | | ECADSR::BIRO | | Wed May 18 1994 17:43 | 91 |
|
Subj: ALEXIS Press Release - ALEXIS Detects HZ43
ALEXIS TEAM RELEASES FIRST CELESTIAL IMAGE
LOS ALAMOS, N.M., May 17, 1994 - Scientists have produced the first
celestial image of a star from X-ray data gathered by Los Alamos National
Laboratory's ALEXIS satellite. The achievement is a significant step toward
creating a Rosetta Stone for decoding the mountain of celestial data ALEXIS
has radioed to Earth in the year since its launch.
The spin-stabilized satellite, launched April 25, 1993, has a significant
wobble due to a damaged solar panel. The damage also left ALEXIS unable to
provide precise information about its orientation as it was originally
designed. The ALEXIS team had to find a new way to determine where any of
the satellite's six X-ray telescopes points at any given moment - essential
for reconstructing an image of the sky.
To create the celestial image, the ALEXIS team used a computer program
developed by AeroAstro, Inc., that defines the satellite's moment-by-moment
orientation. (AeroAstro also built the satellite's central unit and onboard
support systems for power, attitude control and telemetry.) With the
satellite's orientation sufficiently well defined, the team could begin
processing the telescope data.
The image shows a broad slice of the X-ray sky with two bright sources
clearly visible: the Moon and the white dwarf HZ 43, the hot remnant of a
star near the end of its life.
"HZ 43 is the brightest stellar source of soft X rays in the sky, so it's a
good marker for testing the computer code developed to reconstruct the
satellite's orientation," said ALEXIS Project Leader Jeff Bloch. The next
step, Bloch said, is to use the directional information provided by HZ 43 to
refine the computer code and improve its accuracy. After that, the code will
be moved onto a faster machine so the team can begin processing more of the
nine months of archived data.
The observation also is significant, Bloch said, because "the performance of
the instrument is right on the estimates we made based on pre-flight
calibrations. This means that after a year of exposure to the space
environment there has been no serious degradation of the telescope -
mirrors, detectors, filters, it all has to work right."
In the image, the Moon left a short streak as it moved during the
exposure. The doughnut-shaped sky image shows the scan path of the telescope
as the satellite rotates. Bloch and his colleagues are still examining other
textures in the image to determine if they are real celestial emissions or
instrumental and data-processing artifacts.
ALEXIS' X-ray telescopes feature curved mirrors whose multilayer coatings
reflect and focus low-energy X rays the way optical telescopes focus visible
light. The detectors that record the arrival of X-ray photons were built by
a team at the University of California, Berkeley.
The wide-field telescopes - each has a 30-degree field of view - provide new
capabilities for celestial observations, complementary to other missions
currently operating such as NASA's Extreme Ultraviolet Explorer and the
NASA-European Space Agency X-ray satellite called Rosat. When ALEXIS data is
fully decoded, the satellite will provide a unique sky map for studying
celestial emissions of soft X rays.
Already the ALEXIS team has on hand more than 25 compact disks full of data,
each holding 650 megabytes of information (equaling in total more than two
million pages of written text, approximately). About 60 percent of this
information is telescope data; the rest is satellite operational data and
observations from Blackbeard, a broadband radio receiver that records both
manmade and natural radio emissions from Earth.
ALEXIS, which stands for Array of Low-Energy X-ray Imaging Sensors, was
funded by the Department of Energy's Office of Intelligence and National
Security. The $17 million satellite was launched on a U.S. Air Force Pegasus
rocket built by Orbital Sciences Corp.
Because of the initial damage to ALEXIS, the team could not contact the
satellite for the first six weeks after launch, causing them to fear it was
lost. After making contact, the team was able to assess the onboard damage
and develop alternate procedures for controlling the satellite and its
experiments. ALEXIS has been restored to near-normal operations and both
onboard payloads are returning valuable scientific data.
Los Alamos oversaw the satellite's development and built the X-ray telescope
and Blackbeard payloads. The satellite is controlled from a small ground
station at Los Alamos.
Los Alamos National Laboratory is a multidisciplinary research organization
that applies science and technology to problems of national security ranging
from defense to energy research. It is operated by the University of
California for the U.S. Department of Energy.
NOTE: Image mentioned in the release are available via anonymous ftp from
sst.lanl.gov:
cd pub/alexis
contents:
release.txt == this text
captions.txt == figure caption text
figure1.ps == color postscript figure
figure2.ps == color postscript figure
|
| 745.25 | Info available on Mosaic | MTWAIN::KLAES | Houston, Tranquility Base here... | Wed Jul 13 1994 00:30 | 29 |
| From: US4RMC::"[email protected]" "Jeff Bloch" 12-JUL-1994 19:09:52.57
To: [email protected]
CC:
Subj: ALEXIS Info Available on Mosaic
For those of you who are Mosaic junkies, some information and imagery
about ALEXIS is now available on Mosaic. The path is:
http://sst.lanl.gov/
And then select NIS Projects.
I hope to be able to update this page as new information becomes available.
--------------------------------------------------------------------------
Jeffrey Bloch Office: (505) 665-2568
Astrophysics and Radiation Measurements Group ALEXIS Soc: (505) 665-5975
Los Alamos National Laboratory FAX: (505) 665-4414
Group NIS-2, Mail Stop D436 e-mail: [email protected]
Los Alamos, NM 87545
--------------------------------------------------------------------------
% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% Date: Tue, 12 Jul 1994 16:44:44 -0600 (MDT)
% From: Jeff Bloch <[email protected]>
% Subject: ALEXIS Info Available on Mosaic
% To: [email protected]
% Message-Id: <[email protected]>
|
| 745.26 | Newsletter 11 - September 10 | MTWAIN::KLAES | No Guts, No Galaxy | Mon Sep 12 1994 13:24 | 133 |
| From: US1RMC::"[email protected]" "Jeff Bloch" 10-SEP-1994 21:10:40.07
To: [email protected]
CC:
Subj: ALEXIS Electronic Newsleter #11
ALEXIS (Array of Low Energy X-ray Imaging Sensors) E-mail Newsletter # 11.
---------------------------------------------------------------------------
September 10, 1994
For those of you getting this for the first time, this series of
newsletters is sent to those in the astrophysics community that
have expressed an interest in the progress of the ALEXIS project.
ALEXIS Status
-------------
The ALEXIS satellite continues to function normally and we are in dai-
ly contact with it from our Los Alamos ground station. In fact we are
well past the original 1 year design lifetime of the satellite have no
indications of any system degradation (except of course for the origi-
nal launch damage). We continue to collect data with all six ALEXIS
telescopes and have collected over 50 CDROMS (650 MB each) of
data from the satellite thus far. (About 25% of this is spacecraft
housekeeping and attitude sensor data, 25% is Blackbeard RF data, and
50% is x-ray/EUV telescope data). Proper analysis of the time
tagged, photon list data has been delayed by the effects of the launch
damage (the loose solar paddle and broken magnetometer) which have
forced us to devise entirely new methods for attitude reconstruction.
We can now produce attitude solutions with ~1-2 degree precision
and accuracy on a daily basis. This is still short of the 0.25 degree
original specification which matches the FWHM of the telescope spatial
response.
We believe that in the next couple of months we will beat this 2 de-
gree barrier by implementing a model of the spacecraft whose mass
properties vary with thermal input within the attitude reconstruction
algorithm. We have found strong evidence that the mass properties
of the spacecraft change between orbit night and orbit day, and these
changes need to be accurately modeled if the attitude solution code is
to accurately predict the orbit bit night behavior of the spinning
spacecraft. Currently the code uses a fixed set of spacecraft mass
properties. However, even with these 2 degree solutions, the Moon and
HZ43 stick out unambiguous detections in the telescope data.
Analysis of the HZ43 data collected in April of 1994 proves that
even after a year on orbit the telescope response functions are very
similar to what they were in the calibration lab before launch.
For the last month, we have been able to produce attitude solutions
and binned event sky maps in near real time. It currently takes
about 20 minutes to generate a spacecraft attitude solution for 12
hours of data, and then less than 5 minutes to process the events
into a binned sky map using a Sparc 10 class machine. This new capa-
bility can alert for the presence of *bright* EUV transients within
12 hours of the observation. (ALEXIS passes over the Los Alamos
ground station 4 times a day in two sessions separated by 8 to 12
hours due to its 70 degree inclination orbit.) This capability was
put to the test soon after this processing commenced when we thought
we had detected a real EUV transient, possibly a flare star. It
turned out to be false alarm, however, as the source was detected in
the only telescope known to have 3 tiny pinholes in its filter.
Analysis showed the "transient" to be the ultraviolet light leak from
a 3rd magnitude B star that began to scan over the pinhole affected
portion of the detector as the spacecraft's spin axis wandered
across the sky (UV sky survey data anyone?). On the positive side,
such detections provide yet another fiducial for the attitude recon-
struction efforts. In fact, we have recently completed software
that uses point source related events in the telescope data to
calibrate out alignment biases in the attitude solutions.
Since the beginning of telescope operations, we noticed a very pro-
nounced bright background that seemed to persist for 1/2 of a
spacecraft rotation. Our early fears were that this was some geocoron-
al or airglow feature that we had not taken into account adequately
in the design of the telescopes. When the first spacecraft attitude
solutions became available, we noted that the background was not as-
sociated with the earth, the sky, or the earth's magnetic field.
Rather, it seemed best correlated with the angle between each
telescope's field-of-view and the spacecraft velocity vector. At
the July SPIE meeting in San Diego, we had extensive discussions with
members of the ROSAT WFC team who apparently saw the same type of
background. (For a discussion of the WFC background, see Planet.
Space Sci., Vol. 42. No. 1, pp. 71-80, 1994) A preprint of our SPIE
paper discussing this background can be obtained electronically (see
below).
Up to this point, the focus for recovering a science program for
the ALEXIS telescopes has been on the attitude algorithm development.
However, other issues and needs are now arising as medium quaility at-
titude solutions become available. One of the most pressing is the
need to calculate proper effective exposure maps. The launch accident
and the anomalous on-orbit backgrounds that the telescopes observe
rendered invalid all of the assumptions that went into the effective
exposure software that was developed prior to launch. Thus, in order
to properly look for diffuse background features and weak point
sources, we are developing an entirely new effective exposure calcula-
tion code.
ALEXIS Publications - Available Electronically
----------------------------------------------
Uncompressed and compressed Postscript versions of recent ALEXIS
publications and preprints are available via anonymous ftp from
sst.lanl.gov. Go to the directory pub/alexis.
Currently there are two pre-prints from the July SPIE meeting in San Diego:
on_orbit_performance_spie_94.ps - Telescope performance paper
on_orbit_performance_spie_94.ps.Z - Compressed version of telescope
performance paper
ops_paper_spie_94.ps - Satellite Operations paper
ops_paper_spie_94.ps.Z - Compressed version of satellite
ops paper
Disclaimer
----------
This newsletter expresses the opinions of the author and does not
reflect the official positions of LANL, DOE, or the Space Test Program.
--------------------------------------------------------------------------
Jeffrey Bloch Office: (505) 665-2568
Astrophysics and Radiation Measurements Group ALEXIS SOC: (505) 665-5975
Los Alamos National Laboratory FAX: (505) 665-4414
Group NIS-2, Mail Stop D436 e-mail: [email protected]
Los Alamos, NM 87545
--------------------------------------------------------------------------
% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% Date: Sat, 10 Sep 1994 18:47:34 -0600 (MDT)
% From: Jeff Bloch <[email protected]>
% To: [email protected]
% Subject: ALEXIS Electronic Newsleter #11
|
| 745.27 | | ECADSR::BIRO | | Mon Nov 21 1994 11:09 | 29 |
|
From: US4RMC::"[email protected]" "Jeff Bloch" 19-NOV-1994 21:24:02.60
To: [email protected]
Subj: New ALEXIS Images Available on Mosaic
The attitude solutions for ALEXIS have improved dramatically over the last
few months, and some new images of HZ43 in all six ALEXIS telescopes are
available for viewing by opening the path:
http://sst.lanl.gov/projects/alexis.html
And select the line that reads "Select here for the latest ALEXIS
imagery".
A new ALEXIS newsletter will be sent out within a couple of weeks.
(Advance preview: We see more than the Moon and HZ43 these days...)
--------------------------------------------------------------------------
Jeffrey Bloch Office: (505) 665-2568
Astrophysics and Radiation Measurements Group ALEXIS Soc: (505) 665-5975
Los Alamos National Laboratory FAX: (505) 665-4414
Group NIS-2, Mail Stop D436 e-mail: [email protected]
Los Alamos, NM 87545
--------------------------------------------------------------------------
|