| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 640.1 | | 19458::FISHER | Prune Juice: A Warrior's Drink! | Wed Jun 27 1990 13:44 | 6 |
| I suppose there will be yet another fight over the use of (I presume) RTGs to
power it. Actually, I thought I read somewhere that the existing RTGs (Galileo
and Ulysses) could not be replaced because the place that made them no longer
exists. Is that right?
Burns
|
| 640.2 | I saw that *before* Galileo was launched! | 19458::FISHER | Prune Juice: A Warrior's Drink! | Wed Jun 27 1990 13:45 | 2 |
| Obviously the RTGs on Galileo could not be replaced now without some real fancy
footwork on the part of some astronauts! :-)
|
| 640.3 | | 4347::GRIFFIN | Dave Griffin | Wed Jun 27 1990 13:56 | 6 |
| I was under the impression that DOE was planning to start up a reactor
to produce more RTG fuel -- but I may be confusing it with the tritium
producing reactors.
- dave
|
| 640.4 | | STAR::HUGHES | You knew the job was dangerous when you took it Fred. | Wed Jun 27 1990 14:21 | 7 |
| I also recall something about being unable to get new or replenished
RTGs for Galileo and Ulysses due to a DOE plant shutdown.
Its possible that they've switched to a new design using different
materials in the 8 or so years since those probes were built.
gary
|
| 640.5 | Mapping Titan with radar aboard CASSINI | 26523::KLAES | All the Universe, or nothing! | Wed Aug 01 1990 13:28 | 36 |
| Date: 31 Jul 90 06:32:15 GMT
From: (Ron Baalke)
Subject: Titan Probe Article
From "Science News", July 28, 1990
Mapping below the seas of Titan
When the Voyager 1 spacecraft passed Saturn's big moon Titan in
1980, its scientific instruments successfully probed all the way down
to the surface. Titan's dense atmosphere, however, prevented photography
of the terrain, leaving unresolved whether its surface consists of rock,
ice, or a liquid ocean.
Now two scientists note that a radar scheduled to probe Titan as
part of the U.S. Cassini mission in 2002 could map the surface even if
it lies at the bottom of an ocean.
Possible coverings for Titan's surface include water ice, a thick
layer of orgaic sediments and an ocean of liquid methane, ethane and
nitrogren, according to W. Reid Thompson and Steven W. Squyres of
Cornell University in Ithaca, N.Y. The radar NASA is considering in
Cassini's instrument package has a 13.6 centimeter wavelength -- one
capable of penetrating ocean sediment and sediment-ice boundaries,
they write in the August ICARUS. "Hence," they maintain, "such a
sounding mode may offer prospects for investigating the geology of
Titan even if the surface ... is covered locally or globally by a deep
ocean."
___ _____ ___
/_ /| /____/ \ /_ /|
| | | | __ \ /| | | | Ron Baalke | [email protected]
___| | | | |__) |/ | | |___ Jet Propulsion Lab | [email protected]
/___| | | | ___/ | |/__ /| M/S 301-355 |
|_____|/ |_|/ |_____|/ Pasadena, CA 91109 |
|
| 640.6 | Soviet mission plans for Saturn and Titan | ADVAX::KLAES | All the Universe, or nothing! | Mon Aug 27 1990 13:42 | 7 |
| The following is an excerpt from the July/August 1990 issue of
THE PLANETARY REPORT, published by the Planetary Society, page 24:
"Another ambitious mission receiving study-only approval is
TSIOLKOVSKY, a solar probe that would go first to Saturn and drop
off a small probe at Titan."
|
| 640.7 | CRAF-Cassini in danger of cancellation | 4347::GRIFFIN | Dave Griffin | Mon Sep 10 1990 14:18 | 214 |
| From: [email protected] (Jonathan Linine x2789)
Newsgroups: sci.astro
Date: 7 Sep 90 04:56:27 GMT
Organization: Lunar & Planetary Laboratory, Tucson AZ.
Dear colleague,
The solar system exploration program is facing its most serious crisis
since 1980. The Senate budget subcommittee which handles NASA is
preparing to cut approximately $200 million from the space science
programs for FY91. Because the House has already made cuts, there is
little left to remove except a major flight program. EOS is political-
ly untouchable, and rumors are that AXAF must be kept alive at least
as a fiscal buffer for HST repairs. There is therefore a very good
chance that CRAF, and possibly Cassini as well, will be cancelled in
the coming weeks.
If this occurs, NASA will have no approved planetary missions beyond
Mars Observer, and we will have reneged once again on a major agree-
ment with the European Space Agency. The prospects of getting data
within your professional lifetime from any outer planet beyond Ju-
piter, and from any comet or other primitive body will be extremely
dim. To do our best to ensure this does not happen, you must immedi-
ately do the following:
1. Write a letter to Barbara Mikulski and Jake Garn, respectively
chairperson and ranking minority member on the Senate HUD-Independent
Agencies appropriations subcommittee, and to their House counterparts,
Bob Traxler and Bill Green. Addresses are enclosed. Sending letters to
the other sub-committee members too would be an excellent idea. Be
positive--emphasize the good things that have happened in the last
year of space science (Voyager, COBE, Galileo). Do not mention the
Hubble situation. Focus on the importance and value of CRAF and
Cassini--an issue paper is enclosed to help you. Be sure to write as a
private citizen who is also a working scientist--you are representing
yourself, not your institution, but you have knowledge and a very deep
concern which comes from that knowledge.
2. Phone the Senators from your state. Speak to their staffers--tell
the staffers that your Senator must convey to Mikulski and Garn your
concern over and opposition to, any budget cuts in CRAF/Cassini. Also
phone the numbers listed for the subcommittees and register verbally
your support for CRAF/Cassini.
The letter and phone calls are all important. The force most deadly to
a program in jeopardy is silence from its supporters. The Hill
staffers haven't heard much this year from supporters of the planetary
program. Without your written word and phone calls, the door will
close on United States planetary exploration beyond the Galileo and
Mars Observer time frames.
Sincerely,
Jonathan I. Lunine
Associate Professor of Planetary Sciences
CRAF-Cassini Fact Sheet
1. The missions
The Comet Rendezvous Asteroid Flyby (CRAF) mission will be launched in
1995 atop a Titan IV Centaur rocket. After flying past an asteroid,
the spacecraft will rendezvous with Comet Kopff in the year 2000, near
the comet's most distant point from the sun. It will spend about three
years traveling with the comet, observing the changes in activity as
the comet approaches the sun and the ices in the nucleus (the solid
core) sublime. Unlike the very high-speed, quick encounters with comet
Halley, the CRAF spacecraft will slowly orbit about the nucleus, ena-
bling very high-resolution pictures of the nucleus and detailed inves-
tigation of cometary material. A highlight of the mission will come in
the year 2001, when an instrumented penetrator will be fired into the
nucleus from the main spacecraft. The penetrator will spend a week
directly analyzing ice and dust samples in the nucleus, providing us
with a vast amount of detailed chemical and physical information from
this most primitive of solar system bodies.
Cassini will be launched in 1996, and arrive in Saturn orbit in 2002
after flying past an asteroid. Like the CRAF spacecraft, the Cassini
vehicle will be loaded with sophisticated science experiments to ex-
plore in detail the majestic rings, icy moons, turbulent atmosphere
and strong magnetic field of the Saturn system. The highlight of the
mission comes soon after orbit is achieved, when the mother ship
releases the European Space Agency's Huygens probe. Huygens will
plunge into the atmosphere of Titan, Saturn's giant satellite which
has a thick atmosphere and may have surface rains of methane and seas
of liquid ethane. Huygens will make in situ measurements of Titan's
atmosphere as it undergoes a three-hour descent to the surface, and
will take images of clouds and surface features as it nears the sur-
face. Although not designed for guaranteed survival after impact, if a
soft or liquid surface is encountered the probe will relay data from
the surface for a short time. The orbiter will continue to probe Titan
using radar and other systems, making repeated passes by this
organically-rich body as it completes its several-year orbital tour
about Saturn.
2. Science
The CRAF/Cassini program is designed to permit a detailed study of
primordial materials and primitive processes associated with the for-
mation and earliest evolution of the solar system, and the origin of
life. The formation of the solar system, the frequency with which
similar events occur throughout the Galaxy and the implications for
the chemical and physical evolution of the Galaxy are considered
scientific problems of the highest import. Are planets rare or a com-
mon aspect of star formation? Is life a highly improbable phenomenon
or does it occur frequently, given the right conditions? The sampling
of cometary ices, dust and gases, which have been subject to much less
evolution than earth materials, and the investigation of the rich or-
ganic (but presumably non-biological) environment on Titan, will pro-
vide unique information bearing on these issues. The scientific ques-
tions to be addressed by these missions, and the manner in which they
will be addressed, have been reviewed and endorsed by advisory commit-
tees of the National Research Council (National Academy of Sciences).
3. Why do it now?
a) Celestial mechanics: In order to traverse the vast distances to
these objects and complete the missions in a technologically-
reasonable time, the spacecraft must be launched when the intended
targets are in favorable positions in their orbits. As luck would have
it, favorable launch windows open for both of these missions in the
1995 (CRAF) and 1996 (Cassini) time frames. These opportunities are
robust in that a slip by one year caused by unforeseen delays within
the programs can still be accommodated. Beyond that, much longer
trip-times and hence expensive spacecraft redesigns are required. It
is important to consider that today's high school students who are
stimulated to space careers by the pioneering ventures of Voyager,
Magellan and Galileo will be newly-minted Ph.D scientists at the time
CRAF/Cassini enters the prime mission phases.
b) International collaboration: The European Space Agency (ESA) has
already committed to its part of the Cassini mission, i.e., the con-
struction of the Huygens Probe. This joint venture involves closely
coupled collaborations between NASA and ESA in terms of spacecraft
design and construction. ESA chose Cassini in a competition that in-
cluded a proposed collaboration with the USSR among the four rejected
alternatives. Additionally, US and European scientists will be select-
ed for both Probe and Orbiter instruments, making the scientific
analysis of the data truly an international partnership.
Likewise, major elements of the CRAF mission have the involvement of
European scientists, engineers and aerospace firms (portions of the
propulsion module being contributed by West Germany). Successful exe-
cution of the CRAF mission is considered by some to be an important
technical prerequisite for an even more ambitious European concept,
Rosetta, which would return a comet sample to earth around the year
2014. The Europeans are interested in US involvement in the proposed
Rosetta effort, making CRAF/Cassini a litmus test for tightly coupled
joint ventures.
4. Budget issues
CRAF/Cassini was approved as a new start by Congress in FY1990. Under
a pioneering arrangement for such missions, Congress stipulated a cost
cap, 1.6 billion dollars, for total mission development, and mandated
that NASA stay within this limit. NASA is committed to this effort on
cost control, but to do so the agreed-upon allocations in each fiscal
year must be met. Development of sophisticated and pioneering space
missions unavoidably involves very tight planning of schedule and
costs for the entire period from program start to launch. Underfunding
of the program by Congress in any given year would jeopardize severely
NASA's ability to ready the missions for flight on time and within the
1.6 billion dollar limit.
As previously agreed to by NASA and Congress, CRAF/Cassini requires
148.0 million dollars in fiscal year 1991 to stay on track to the 1995
and 1996 launches.
5. The payoffs
The United States rose to a leadership position in science and tech-
nology during and after World War II. That leadership has been seri-
ously challenged in recent years in a wide range of fields. The United
States program of solar system exploration is one of only a handful of
areas in which we are unquestioned as the leader in both technology
and the scientific harvest derived therefrom. No other nation has been
capable of mounting long-duration missions to the outer solar system
such as Voyager. With CRAF/Cassini, we build on that achievement with
new technologies which will provide actual contact with, and in-depth
exploration of, bodies in the outer solar system. Although we have
collaborators in Europe, the US role in these missions is that of the
leader. Thus, we have the best of both worlds: international coopera-
tion in a mission set for which the US clearly takes the primary role.
The output of planetary missions is new information on the unexpected
wealth of physical phenomena in the solar system, enhanced understand-
ing of the laws of nature, and further progress on the questions of
the origin of the solar system, its planets, earth and life itself.
The planetary exploration program has rewritten the textbooks on space
science over the past quarter century, and filtered into the popular
media, part of the expanding world view of ourselves as a species.
This enriching view is extended and renewed with each new foray into
the solar system.
The benefits of planetary exploration in the educational arena are
thus not just to attract students into space sciences, but to provide
a dramatic and understandable framework within which all may experi-
ence and learn more about science. Learning about science by use of
materials derived from the planetary program has demonstrated appeal
to individuals at all levels of scientific understanding.
Our perspective about ourselves and our place in the universe has been
changed forever by the new age of exploration we find ourselves in and
this vision is far from complete.
--------------------
Jonathan I. Lunine
Associate Professor of Planetary Sciences
[email protected]
|
| 640.8 | Missed my mark... | 4347::GRIFFIN | Dave Griffin | Mon Sep 17 1990 17:00 | 36 |
| I've been studying up on the CRAF and Cassini missions over the weekend
so I could write my letter to the various senators expressing my
endorsement of the missions -- as I have found them to be well worth
saving.
Unfortunately, I found out that the axe has already fallen in the
budget committee, and the bill is now in the appropriations committee.
I wish I had time last week to work on this - but it looks like I
blew it.
[The Senate VA, HUD and Independent Agencies subcommittee
yesterday cut $1.67 billion from the Administration's $15.1
billion NASA budget request. This included $863.6 million from
the request for Space Station Freedom, $210 million from studies
and technology programs associated with the Space Exploration
Initiative, and $37 million from exploration mission studies.
The bill next will be considered by the full Senate
Appropriations Committee. Earlier this summer, the House of
Representatives approved a FY '91 budget of $14.3 billion for
NASA.
NASA Headline News - 9/14]
If I interpret this verbatim, then the missions may well be intact,
but those interested in saving CRAF/Cassini have lost their specialized
audience. Sigh!
[Mind you, I'm *still* going to write my letters -- just in case.]
If people are interested, I can post the results of my research on
these missions and why I believe they should be given the go-ahead.
The area of planetary exploration has been fascinating to learn about,
and they have worked hard to live (and thrive) in tight fiscal budgets.
- dave
|
| 640.9 | Payload for CASSINI's Titan probe, HUYGENS | ADVAX::KLAES | All the Universe, or nothing! | Thu Oct 18 1990 15:58 | 49 |
| From: [email protected] (Ron Baalke)
Newsgroups: sci.space,sci.astro
Subject: Titan Probe Payload Selected
Date: 18 Oct 90 16:53:50 GMT
Sender: [email protected]
Organization: Jet Propulsion Laboratory, Pasadena, CA.
The Science Programme Commitee meeting help on September 17-18,
1990 at the Eurpean Space Agency (ESA) headquarters in Paris, France,
approved the selection of the following payload for the Titan probe,
Huygens, of the Cassini mission to Saturn:
o ASI (Atmospheric Structure Instrument) - measures the temperature and
pressure of the atmosphere, winds and turbulance, and the
atmosphere electricity.
o GCMS (Gas Chromatograph) - measures the composition of the atmosphere
during descent.
o ACP (Aerosol Collector and Pyrolyser) - samples aerosols suspended
in the atmosphere, and analyzes their composition.
o DISR (Descent Imager/Spectral) - makes spectral measurements in
several wavelengths from the ultraviolet to the near infrared and
will take pictures of the clouds and of the ground.
o SSP (Surface Science Package) - provides fundamental information on
the state (liquid, semi-liquid, solid) of Titan's surface at the
point of touchdown.
o DWE (Doppler Wind Experiment) - measures zonal wind characteristics
with very high accuracy.
The Science Programme Committee also recommends that NASA and ESA
do their best to accomodate two other instruments on the Huygens probe:
o Nephelometer - measures aerosol size and distribution, possibly use
a refurbished Galileo nephelometer
o Altimeter - measures the distance between the probe and the ground
during descent; also provides information on surface roughness.
___ _____ ___
/_ /| /____/ \ /_ /|
| | | | __ \ /| | | | Ron Baalke | [email protected]
___| | | | |__) |/ | | |___ Jet Propulsion Lab | [email protected]
/___| | | | ___/ | |/__ /| M/S 301-355 |
|_____|/ |_|/ |_____|/ Pasadena, CA 91109 |
|
| 640.10 | CASSINI/CRAF Update - November 9 | ADVAX::KLAES | All the Universe, or nothing! | Mon Nov 12 1990 16:12 | 135 |
| From: [email protected] (Ron Baalke)
Newsgroups: sci.space,sci.astro
Subject: CRAF/Cassini Update - 11/09/90
Date: 11 Nov 90 00:19:24 GMT
Sender: [email protected]
Organization: Jet Propulsion Laboratory, Pasadena, CA.
CRAF/Cassini Status Report
November 9, 1990
The good news concerning the CRAF/Cassini mission, is that it
looks like both missions will be funded. Congress approved both
missions earlier in the year, but during the recent budget
negotiations, it looked like that the CRAF portion was not going to be
funded. The total budget for both missions is 1.6 billion dollars,
with 145 million needed in the 1991 fiscal year budget to get the
projects started. Only 95 million was approved - being 50 million
short, things were looking grim for the CRAF mission, as the Cassini
mission has priority. However, most of the 50 million has since been
restored which should enable the start of both the CRAF and Cassini
missions.
The CRAF/Cassini missions will be the first to use the next
generation spacecraft using the Mariner Mark II design. The CRAF
spacecraft (Comet Rendezvous Asteroid Flyby) will meet with the Comet
Kopff near the orbit of Jupiter and travel along side it for at least
three years. It will also launch a penetrator which will directly
sample the comet's nucleus. On the way to to Comet Kopff, CRAF will
flyby the asteroid Hamburga. JPL is currently in negotiations with
the McDonald's hamburger franchise to arrange some kind of advertising
deal (this is no joke).
Key Scheduled Dates for the CRAF Mission
--------------------------------------------
08/22/95 - Titan IV/Centaur Launch
01/22/98 - 449 Hamburga Asteroid Flyby
08/14/00 - Comet Kopff Arrival
08/20/01 - CRAF Penetrator to Kopff
03/31/03 - End of Primary Mission
The Cassini mission will go to Saturn, using gravity assists from
Earth and Jupiter. This trajectory is called EJGA (Earth-Jupiter
Gravity Assist). A probe named Huygens will be dropped off at
Saturn's largest moon, Titan. The Cassini mission is an international
mission. The European Space Agency (ESA) will supply the Huygens
probe, Germany will supply the propulsion module, and Italy will
provide the High Gain Antenna, sun sensors, and radio science
instruments. ESA has already approved the science instruments that
will be on the Titan probe. NASA has selected the science instruments
that will be onboard the Cassini orbiter; however, this list is not
quite official yet -- it is sitting on the desk of Richard Truly,
NASA's administrator, awaiting his signature.
Key Scheduled Dates for the Cassini Mission (EJGA Trajectory)
-------------------------------------------------------------
08/22/96 - Titan IV/Centaur Launch
03/29/97 - 66 Maja Asteroid Flyby
06/08/98 - Earth Gravity Assist
02/06/00 - Jupiter Gravity Assist
12/06/02 - Saturn Arrival
03/27/03 - Titan Probe Release
03/29/03 - Orbiter Deflection Maneuver
04/18/03 - Titan Probe Entry
06/30/03 - Iapetus Flyby
05/20/04 - Dione Flyby
09/12/04 - Enceladus Flyby
08/14/05 - Iapetus Flyby
12/31/06 - End of Primary Mission
The Maja asteroid that Cassini will encounter is a type C
asteroid, 39 kilometers in size.
When Cassini arrives at Saturn in December, 2002, it will
perform a SOI (Saturn Orbit Insertion) burn. The spacecraft will
actually pass through the outer rings of Saturn during SOI, passing
between the F and G rings at a distance of 2.6 Saturn radii from the
planet. After SOI, the Huygens probe will be released on the
subsequent orbit. Two days after probe release, the Cassini orbiter
will perform a deflection manuever. This deflection maneuver serves
two purposes: it ensures the Cassini orbiter doesn't follow the
Hugyens probe into Titan, and it positions the orbiter to lag behind
the probe about 3.5 hours so that science data can be received from
the Huygens probe as it descends into the atmosphere of Titan. It
will take the Huygens probe about 3 hours to parachute all the way
down to the surface of Titan; if the probe survives the landing,
valuable data will continue to be transmitted back for about 30 more
minutes. No more data will be returned to the Cassini orbiter from
Huygens on any subsequent orbits, as the battery onboard Huygens will
have rundown by then.
During its four year orbital tour of Saturn, Cassini will make 60
orbits of the planet. Compare this with Galileo, which will make
about 10 orbits around Jupiter in two years. Galileo has the luxury
of using gravity assists of the four large Galileon moons (Io, Europa,
Ganymede and Callisto), while at Saturn, there is only one large moon,
Titan, that Cassini can take advantage of. Because of this, Cassini
will make close flybys of Titan on 35 of the 60 orbits. Each Titan
flyby is designed so that the Cassini will be deflected a little
further out of Saturn's ecliptic plane, so that at the end of four
years, the spacecraft will be in polar orbit around Saturn at an
inclination of between 80 to 90 degrees. A polar orbit puts Cassini
into a unique advantage point where many star occultations can be
observed through Saturn's rings. Cassini will be carrying a Titan
Radar Mapper which it will use to map the surface of Titan during its
numerous flybys of the moon. The Titan Radar Mapper is a SAR
(Synthetic Aperture Radar), similiar to the one used by the Magellan
spacecraft at Venus.
Also, still being looked at, are alternate trajectory routes to
Saturn. A VEJGA (Venus-Earth-Jupiter Gravity Assist) trajectory has
been developed which would use an additional gravity assist of Venus.
This trajectory has the advantage of reducing the launch energy, which
in turn, means a heavier payload can be launched. Note that the VEJGA
trajectory is only preliminary, and the EJGA trajectory is still the
official route that Cassini will take.
Key Dates for the Cassini Mission (VEJGA Trajectory)
----------------------------------------------------
11/28/95 - Titan IV/Centaur Launch
12/04/96 - Venus Gravity Assist
07/05/98 - Earth Gravity Assist
11/11/98 - Clarissa Asteriod Flyby
03/28/00 - Jupiter Gravity Assist
12/07/03 - Saturn Arrival
This trajectory will have Cassini pass near the Clarissa
Asteroid, a type F asteroid which is 21 kilometers in size.
___ _____ ___
/_ /| /____/ \ /_ /|
| | | | __ \ /| | | | Ron Baalke | [email protected]
___| | | | |__) |/ | | |___ Jet Propulsion Lab | [email protected]
/___| | | | ___/ | |/__ /| M/S 301-355 |
|_____|/ |_|/ |_____|/ Pasadena, CA 91109 |
|
| 640.11 | CASSINI projects and investigators selected | ADVAX::KLAES | All the Universe, or nothing! | Wed Nov 14 1990 15:00 | 264 |
| From: [email protected] (Ron Baalke)
Newsgroups: sci.space,sci.astro
Subject: NASA Select Cassini Investigators (Forwarded)
Date: 13 Nov 90 22:38:26 GMT
Sender: [email protected]
Organization: Jet Propulsion Laboratory, Pasadena, CA.
NASA SELECTS INVESTIGATIONS FOR CASSINI SATURN ORBITER MISSION
NASA has selected the principal investigators and science
teams for the Saturn Orbiter portion of the Cassini mission,
scheduled for launch in 1996. The investigators come from 11
U.S. universities, 3 NASA centers and 3 other U.S. laboratories
as well as 13 foreign countries.
The Saturn Orbiter will include 62 investigations
encompassing analysis of the structure and composition of
Saturn's atmosphere, the physical properties of ring particles, a
survey of moonlets within the rings and a close look at several
moons. The Cassini Saturn Orbiter also will deploy the Huygens
Probe, supplied by the European Space Agency (ESA), which will
descend through the atmosphere to the surface of Saturn's moon
Titan.
The Cassini mission is named after the 17th century
astronomer Jean Dominique Cassini who discovered several of
Saturn's moons and the major divisions of its rings. The first
spacecraft to visit Saturn since the 1981 flyby by Voyager 2,
Cassini will stay within the Saturnian system for 4 years and
pass within a few hundred kilometers of several of Saturn's
moons. Cassini's onboard cameras will take detailed pictures of
the intensely cratered surfaces of the icy moons, map their
topography with high-resolution radar and determine the surface
composition with spectroscopic instruments.
Onboard radar also will map a large portion of Titan's
cloud-shrouded surface, much like the Magellan mission at
Venus. Instruments on both the Orbiter and the Probe will
investigate the chemical processes that produce the large moon's
unique atmosphere. These processes may resemble the
prebiological chemical evolution which took place on the
primitive Earth.
The Probe, named for the 17th century scientist Christian
Huygens who discovered the true shape of Saturn's rings, will
examine the atmosphere and clouds and takes pictures of the
surface during its 3-hour descent. If it survives the landing,
the Huygens Probe will continue to make measurements and relay
data to the Saturn Orbiter until it loses radio contact. One
intriguing question that scientists hope Cassini will answer is
whether there are oceans of liquid hydrocarbons on the moon's
surface resulting from photochemical processes in Titan's upper
atmosphere. ESA recently announced the selection of
investigations to be conducted by the Cassini Huygens Probe.
The investigators also will examine the interactions of
Saturn's magnetosphere with dust and moonlets in the rings and
with Titan's atmosphere. This study will enable scientists to
gain an understanding of the processes involving interaction of
plasma, dust and radiation which were important during the
formation of planets in the early solar system.
Cassini's trajectory to Saturn takes it through the asteroid
belt and close to Jupiter for a gravity-assist flyby. This
trajectory will allow investigators to study an asteroid and make
observations of the Jovian system in addition to its planned
study of the Saturnian system, complementing the missions of
combined into a sing NASA to enhance their ability to
pursue common scientific objectives and reduce the overall
development cost. Both spacecraft are based on the Mariner Mark
II design with much of the flight hardware identical except for
minor modifications for unique science investigations.
Cassini is a joint project of NASA and ESA. Cassini mission
development and operations will be conducted by NASA's Jet
Propulsion Laboratory in Pasadena, Calif. John Casani is the
Project Manager and Dr. Dennis Matson is the Project Scientist.
The CRAF/Cassini Program is managed by the Office of Space
Science and Applications, NASA Headquarters, Washington, D.C.
___ _____ ___
/_ /| /____/ \ /_ /|
| | | | __ \ /| | | | Ron Baalke | [email protected]
___| | | | |__) |/ | | |___ Jet Propulsion Lab | [email protected]
/___| | | | ___/ | |/__ /| M/S 301-355 |
|_____|/ |_|/ |_____|/ Pasadena, CA 91109 |
From: [email protected] (Ron Baalke)
Newsgroups: sci.space,sci.astro
Subject: Cassini Investigation Team (Forwarded)
Date: 13 Nov 90 23:04:29 GMT
Sender: [email protected]
Organization: Jet Propulsion Laboratory, Pasadena, CA.
INVESTIGATIONS SELECTED FOR THE CASSINI SATURN ORBITER
INVESTIGATION ACCOMMODATION PHASE
PRINCIPAL INVESTIGATOR, INSTRUMENT PAYLOAD
Virgil G. Kunde, Infrared Fourier Spectrometer, NASA Goddard
Space Flight Center
Eberhard Grun, Cosmic Dust Analyzer, Max-Planck-Institut fuer
Kernphysik, Federal Republic of Germany
Donald A. Gurnett, Plasma and Radio Wave System, University of Iowa
David T. Young, Plasma Spectrometer, Southwest Research Institute
Larry W. Esposito, Ultraviolet Spectrometer and Imager,
University of Colorado
Stamatios M. Krimigis, Magnetospheric Imaging Instrument, Johns
Hopkins University
David J. Southwood, Dual Technique Magnetometer, Imperial
College, United Kingdom
INTERDISCIPLINARY SCIENTISTS
Tobias C. Owen, Atmospheres, University of Hawaii
Jeffrey N. Cuzzi, Rings and Dust, NASA Ames Research Center
Laurence A. Soderblom, Satellites and Asteriods, U.S. Geological Survey
Michel Blanc, Magnetosphere and Plasma, Observatoire Midi-
Pyrenees, France
Tamas I. Gombosi, Magnetosphere and Plasma, University of Michigan
James B. Pollack, Origin and Evolution, NASA Ames Research Center
Darrell F. Strobel, Aeronomy and Solar Wind Interaction, Johns
Hopkins University
FACILITY INSTRUMENT TEAMS
Titan Radar Mapper:
Charles Elachi, NASA Jet Propulsion Laboratory, Team Leader
Randolph L. Kirk, U.S. Geological Survey
Chris G. Rapley, University College, United Kingdom
Giovanni Picardi, Universita di Roma, Italy
Charles A. Wood, University of North Dakota
Steven J. Ostro, NASA Jet Propulsion Laboratory
Howard A. Zebker, NASA Jet Propulsion Laboratory
Imaging Science Subsystem:
Carolyn C. Porco, University of Arizona, Team Leader
Gerhard Neukum, Deutsche Agentur fuer Raumfahrtangelegenheiten
GmbH, Federal Republic of Germany
Steven W. Squyres, Cornell University
Peter C. Thomas, Cornell University
Alfred S. McEwen, U.S. Geological Survey
Torrence V. Johnson, NASA Jet Propulsion Laboratory
Joseph Veverka, Cornell University
Henry C. Dones, Jr., University of Toronto, Canada
Carl D. Murray, University of London, United Kingdom
Joseph A. Burns, Cornell University
Andre Brahic, Observatoire de Paris-Meudon, France
Anthony D. Del Genio, NASA Goddard Institute for Space Studies
Andrew P. Ingersoll, California Institute of Technology
Robert A. West, NASA Jet Propulsion Laboratory
Radio Science Subsystem:
Arvydas J. Kliore, NASA Jet Propulsion Laboratory, Team Leader
Andrew F. Nagy, University of Michigan
F. Michael Flasar, NASA Goddard Space Flight Center
Richard G. French, Wellesley College
Essam A. Marouf, Stanford University
John D. Anderson, NASA Jet Propulsion Laboratory
Nicole Borderies, Observatoire Midi-Pyrenees, France
Hugo D. Wahlquist, NASA Jet Propulsion Laboratory
Bruno Bertotti, Universita di Pavia, Italy
Luciano Iess, Istituto di Fisica dello Spazio Interplanetario, Italy
Ion and Neutral Mass Spectrometer:
A Facility Instrument Definition Team is to be appointed. A
Science Team will be solicited through a separate announcement
of opportunity.
Visual and Infrared Mapping Spectrometer:
Facility Instrument approved for Investigation Accommodation
Phase; to be included in payload only if resources permit.
Robert H. Brown, NASA Jet Propulsion Laboratory, Team Leader
Dale P. Cruikshank, NASA Ames Research Center
Roger N. Clark, U.S. Geological Survey
Andrea Carusi, Istituto di Astrofisica Spaziale, Italy
Angioletta Coradini, Istituto di Astrofisica Spaziale, Italy
Jean-Pierre Bibring, Universite de Paris Sud-Orsay, France
Christophe Sotin, Universite de Paris Sud-Orsay, France
Yves Langevin, Universite de Paris Sud-Orsay, France
Robert M. Nelson, NASA Jet Propulsion Laboratory
Ralf Jaumann, Deutsche Agentur fuer Raumfahrtangelegenheiten
GmbH, Federal Republic of Germany
Dennis L. Matson, NASA Jet Propulsion Laboratory
Kevin H. Baines, NASA Jet Propulsion Laboratory
Vittorio Formisano, Istituto Fisica Plasma Interplanetario, Italy
Michael Combes, Observatoire de Paris-Meudon France
Pierre Drossart, Observatoire de Paris-Meudon, France
Bruno Sicardy, Observatoire de Paris-Meudon, France
___ _____ ___
/_ /| /____/ \ /_ /|
| | | | __ \ /| | | | Ron Baalke | [email protected]
___| | | | |__) |/ | | |___ Jet Propulsion Lab | [email protected]
/___| | | | ___/ | |/__ /| M/S 301-355 |
|_____|/ |_|/ |_____|/ Pasadena, CA 91109 |
|
| 640.12 | NASA and ESA sign agreement for a joint Saturn mission | PRAGMA::GRIFFIN | Dave Griffin | Fri Jan 04 1991 13:18 | 49 |
| From: [email protected] (Peter E. Yee)
Date: 3 Jan 91 21:15:21 GMT
Organization: NASA Ames Research Center, Moffett Field, CA
Debra J. Rahn
Headquarters, Washington, D.C. January 3, 1991
(Phone: 202/453-8455)
Paula Cleggett-Haleim
Headquarters, Washington, D.C.
(Phone: 202/453-1547)
RELEASE: 91-1
NASA AND ESA SIGN AGREEMENT FOR A JOINT SATURN MISSION
NASA and European Space Agency (ESA) officials recently
signed an agreement to cooperate in the development of the
Cassini spacecraft to study Saturn. NASA Administrator Richard
H. Truly and ESA Director-General Jean-Marie Luton signed the
agreement.
The Cassini spacecraft will explore the Saturnian system,
which contains a host of volatile-rich bodies with a record of
processes that have modified these bodies. The Cassini
spacecraft will be composed of the Saturn Orbiter provided by
NASA and the Huygens Probe System provided by ESA. It is
currently scheduled for launch by NASA on a Titan IV/Centaur
vehicle in April l996. NASA will provide overall Cassini mission
operations and ESA will support probe operations.
The flight trajectory requires approximately 7 years from
launch to Saturn orbital insertion. Once at the Saturnian
system, the mission baseline lifetime is 4 years.
The Saturn Orbiter will deliver the Huygens Probe to Titan
and will make repeated close flybys of Titan to allow intensive
study of this moon of Saturn. The mission also will conduct
detailed observations of several other moons of Saturn, the
Saturnian rings, atmosphere and magnetosphere.
Enroute to Saturn the spacecraft will pass through the
asteroid belt and make observations of a least one asteroid, and
thereafter fly by Jupiter making observations of the planet and
its environment.
|
| 640.13 | Launch now Nov '95 | ELIS::GARSON | V+F = E+2 | Fri Nov 08 1991 10:27 | 58 |
| ESA NEWSLETTER
ISSUE #5
MAY 1991
NEW ROUTE TO SATURN AND TITAN
The planned launch of the joint ESA/NASA Huygens/Cassini mission to Saturn has
been brought forward by five months to November 1995. Project officials have
established that this new launch window will allow them to carry more
scientific instruments to the Ringed Planet. "This new opportunity means we can
launch a total mass of six, instead of five tonnes", says ESA's Project
Scientist, Jean-Pierre Lebreton.
The mission is named after two European scientists who discovered the rings and
largest moon of Saturn, Titan. NASA's Jet Propulsion Laboratory (JPL) in
Pasadena, California, is providing the Cassini orbiter which will carry the
ESA's Huygens probe to Titan. The joint mission will follow on from the Voyager
spacecraft, which encountered the Saturn system ten years ago.
JPL engineers have recently identified a more energy-efficient route for
Cassini known as Venus-Earth-Jupiter-Gravity Assist (VEJGA). After launch in
November 1995, Huygens/Cassini will head in towards the Sun, making two full
orbits around the Sun. By the end of its second orbit in December 1996, the
spacecraft will encounter Venus and use the planet's gravity to "boost" it
towards the Earth for a July 1998 encounter. It will use the Earth's
gravitational field to pick up speed and head towards the outer Solar System,
passing by asteroid Clarissa in November 1998. It will then get a further
"gravity assist" from Jupiter in March 2000, before reaching Saturn in December
2003. "Although we launch sooner, we arrive later," says Jean-Pierre Lebreton.
"But there is no impact on the scientific mission of Huygens/Cassini."
After arriving in orbit around Saturn, ESA's Huygens probe will be dispatched
towards Titan. The probe is housed inside an aerodynamically-designed "shell".
This will protect it from the intense frictional heating resulting from its
descent through Titan's dense atmosphere at hypersonic speeds. The shell acts
to decelerate the probe and, by the use of a mortar, a drogue parachute is
released about 200 kilometres above the surface. Once the main parachute has
opened, direct measurements of pressure, temperature, chemical composition and
cloud particles will begin.
The surface of Titan is totally obscured by a dense, orange-coloured atmosphere.
It is predominantly made up of nitrogen, with methane making up a few percent
of the atmosphere. The action of sunlight on methane results in the creation of
complex organic polymers - complicated chains of carbon-containing molecules.
As a result, Titan contains the basic ingredients out of which primordial life
developed on Earth. But the average temperature at the surface of Titan is
-180�C so there is no chance of finding life there today.
The atmosphere pressure at the surface of Titan is roughly 1 1/2 times that at
sea level on Earth. Coupled with the freezing conditions, this means that
Titan's surface is close to the triple point of methane - where it can exist as
a solid, liquid or gas. This means there may be cliffs of solid methane or
methane icebergs in a liquid ethane/methane ocean. Alternately, there may be a
cloud layer which gives rise to methane rain or snowflakes. "There has been a
great deal of speculation" says Jean-Pierre Lebreton. "The simple answer is -
we'll have to wait for Huygens!" Although the probe is not designed to survive
landing, the scientists hope that it will survive for a few minutes and take
measurements and samples of the surface.
|
| 640.14 | RE 640.13 | MTWAIN::KLAES | All the Universe, or nothing! | Fri Nov 08 1991 12:21 | 5 |
| According to Note 667.8, the CASSINI launch date has now been
moved to 1997.
Larry
|
| 640.15 | | ELIS::GARSON | V+F = E+2 | Mon Nov 11 1991 02:31 | 5 |
| re .14
Perhaps Huygens is going on ahead . . . (-:
P.S. Thanks for putting me right.
|
| 640.16 | ESA Bulletin articles on CASSINI/HUYGENS | MTWAIN::KLAES | All the Universe, or nothing! | Mon Jan 20 1992 16:46 | 71 |
| Article: 19645
From: [email protected] (Bill Higgins-- Beam Jockey)
Newsgroups: sci.space,sci.astro
Subject: Re: Jupiter and Titan atmospheric probes
Date: 17 Jan 92 01:57:03 GMT
Sender: [email protected]
Organization: Fermi National Accelerator Lab
I knew that one day my role as The Man Who Saves Magazines would be
vindicated. Enzo Liguori ([email protected]) wrote:
>Could anyone provide me informations about the experiments that will
>be carryed out by the Jupter atmospheric probe and by the subprobe
>Huygens ?
I looked in my ESA pile and found all the articles dealing with
Huygens/Cassini.
J.-P. Lebreton and G. Scoon
"Cassini-- A Mission to Saturn and Titan"
*ESA Bulletin* no. 55, August 1988, p. 24
(Nice overview, though it offers only a Phase A version of the probe
payload. It was not dubbed Huygens until later.)
W. Berry and J. Haeuser
"Space-Vehicle Aerothermodynamics"
*ESA Bulletin* no. 64, November 1990, p. 6
(Includes a brief discussion and a couple of color pictures of the Huygens
probe, nothing about instrumentation)
G. Scoon, G. Whitcomb, M. Eiden, A. Smith
"Cassini/Huygens Entry and Descent Technologies"
*ESA Journal* Vol. 13 no. 3 (89/3 or 3rd quarter 1989), p. 175
(Descent trajectory parameters, aerodynamics, parachute, etc.)
A. Ciarlo and K. Schilling
"Application of Expert System Techniques to the Cassini Titan Probe"
*ESA Journal* Vol. 12 no. 3 (88/3 or 3rd quarter 1988), p. 319
(Considerable technical detail about the mission, despite the title)
Here's the list of Huygens instruments given by Lebreton and Scoon:
Atmospheric structure instrument
Probe infrared laser spectrometer
Gas chromatograph/neutral mass spectrometer
Aerosol collector and pyrolyser
Descent imager/spectral radiometer
Lightning and radio-emission detector
Surface-science package
Doppler wind experiment (tracking probe from orbiter)
Radar altimeter science
I'll bet there have been changes in this since the 1988 article, and
that quite a bit of development has been done on the instruments.
To read about the Galileo instruments, the best source is good old
NASA SP-479, *Galileo: Exploration of Jupiter's System*. It's out of
print, so you'll have to find it in a library. Principal author was
C.M. Yeates, with co-authors T.V. Johnson, L. Colin, F.P. Fanale, L.
Frank, and D.M. Hunten.
______meson Bill Higgins
_-~
____________-~______neutrino Fermi National Accelerator Laboratory
- - ~-_
/ \ ~----- proton Bitnet: [email protected]
| |
\ / SPAN/Hepnet/Physnet: 43011::HIGGINS
- -
~ Internet: [email protected]
|
| 640.17 | Trimming CASSINI | VERGA::KLAES | All the Universe, or nothing! | Wed Mar 11 1992 09:46 | 27 |
| From: DECWRL::"[email protected]" 9-MAR-1992
20:57:33.57
To: [email protected]
Subj: NASA Reduces Size & Cost of Cassini
This is a summary of an article from the Space News newspaper titled
"NASA Reduces Size, Cost of Cassini Spacecraft", March 2-8, 1992.
Due to the tight budget, NASA had decided to trim the size and cost of
the Cassini mission to Saturn. The spacecraft's mass is expected to
be trimmed by 20%, or 1300 kg, off the total spacecraft mass of 6,600
kg. One of the vulnerabilities of the mission is the requirement for
a upgraded SRM's on the Titan 4 booster which currently do not exist,
and have been experiencing problems in their development. One of the
upgraded SRM's exploded in April 1991 during a ground test. The
weight reduction of the spacecraft will allow it to fit on a standard
Titan 4. It is hoped that only 250 kg will have to come from the
spacecraft itself, with the remainder of the reduction coming from the
on-board propellant load.
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ M/S 525-3684 Telos | In the middle of difficulty
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | lies opportunity --
|_____|/ |_|/ |_____|/ | Albert Einstein
|
| 640.18 | | CLOSUS::TAVARES | John-Stay low, keep moving | Wed Mar 11 1992 13:34 | 2 |
| Sounds like a good way to test the US interface with Energia as
preparation for the Freedom activities.
|
| 640.19 | | AUSSIE::GARSON | | Wed Mar 11 1992 21:51 | 11 |
| re .18
>Sounds like a good way to test the US interface with Energia as
>preparation for the Freedom activities.
Wouldn't Energia be overkill for launching Cassini?
According to 291.* Energia can put 100,000kg in LEO.
As you say though, if Energia is to be used at all by NASA then they
have to start somewhere with interfacing etc.
|
| 640.20 | Cassini Design Review | PONIL::J_BUTLER | E pur, si muove... | Thu Dec 10 1992 16:06 | 101 |
| Article 2634 of sci.space.news:
Newsgroups: sci.space.news
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From: [email protected] (Ron Baalke)
Subject: Cassini Undergoes Intensive Design Review
Message-ID: <[email protected]>
Followup-To: sci.space
News-Software: VAX/VMS VNEWS 1.3-4
Keywords: Cassini, JPL
Sender: [email protected] (Usenet)
Nntp-Posting-Host: kelvin.jpl.nasa.gov
Reply-To: [email protected]
Organization: Jet Propulsion Laboratory
Date: Thu, 10 Dec 1992 13:33:56 GMT
Approved: [email protected]
Lines: 82
From the "JPL Universe"
December 4, 1992
Milestones, project-wide review in sight for Cassini
By Franklin O'Donnell
JPL's Saturn-bound Cassini mission is in the midst of
passing several major milestones, with a critical project-wide
review planned next week and recent reviews of the spacecraft's
Titan probe and science payload.
The critical design review, which will take an exhaustive
look at the mission and all major spacecraft systems, is
scheduled Dec. 8 at the Pasadena Hilton and Dec. 9-11 in JPL's
von Karman Auditorium.
The mission's Huygens Titan probe, meanwhile, was the topic
of a system design review Oct. 12-16 at the Cannes, France,
facility of Aerospatiale, which is building the probe for the
European Space Agency.
And plans among scientists whose instruments will ride on
Cassini solidified this fall when NASA formally confirmed the
mission's science payload.
"All of the project's elements are moving forward very
briskly," said Cassini Project Manager Dick Spehalski. "The
critical design review will be an important step in the process
of designing and building the spacecraft."
Next week's meetings will include a comprehensive review of
the project --spanning how it responds to science objectives, as
well as Cassini mission design, orbiter systems, probe and
launch-vehicle interface.
In addition to JPL staff members, the review will include
presentations by Dr. Hamid Hassan, ESA project manager for the
Huygens probe, and Dr. Romeo Pernice of the Italian space agency,
which is contributing Cassini's high-gain antenna.
JPL Cassini Project Scientist Dr. Dennis Matson noted that
science teams were very pleased by NASA's recent confirmation of
the Cassini orbiter's 12 experiments. Another six fly on ESA's
Huygens probe.
Although the science instruments were tentatively selected
in 1990, they were then subject to scrutiny during an
"accommodation phase" during which the cost, weight and power
needs of each experiment were carefully eyed.
Matson credited JPL organizations with delivering "excellent
packages" on plans for science instruments that were among the
most challenging to bring in on a tight budget.
JPL's Office of Space Science and Instruments is building
the visual and infrared mapping spectrometer (VIMS) and the Titan
radar mapper, while the Observational Systems Division is
fabricating Cassini's optical cameras.Matson said science teams
are now turning their attention to the ground system "and more
detailed work on how we will go about flying this spacecraft."
As for the Huygens probe, the green light at the October
meeting in France paved the way for work to proceed, leading up
to hardware deliveries in 1996 and 1997, according to Herb
Phillips, JPL's Huygens technical integration manager.
In all, ESA will deliver three versions of the Huygens probe
to the United States.
The first, an engineering model to be used during Cassini
integration in JPL's Spacecraft Assembly Facility, will arrive
on-Lab in February 1996.
A second copy of the probe, called the structural thermal
pyro model, will be delivered at JPL in June 1996. This model
will be used for environmental testing in the Space Simulator.
The third copy of the probe -- the actual flight model --
will be delivered directly to Kennedy Space Center in May 1997
for integration with the spacecraft at the launch site.
The Cassini orbiter will be built up in JPL's Spacecraft
Assembly Facility between September 1995 and May 1996. It will
then undergo tests through spring 1997, when it will be shipped
to Florida to be prepared for its October 1997 launch.
After flybys of Venus (twice), Earth and Jupiter as it loops
around the sun to pick up energy, Cassini will arrive at Saturn
in November 2004, beginning a four-year orbital tour of the
ringed planet and its 18 moons. The Huygens probe will descend to
the surface of Titan in June 2005.
###
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ M/S 525-3684 Telos | The 3 things that children
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | find the most fascinating:
|_____|/ |_|/ |_____|/ | space, dinosaurs and ghosts.
|
| 640.21 | Cassini Saturn mission, spacecraft finalized | PRAGMA::GRIFFIN | Dave Griffin | Wed Dec 16 1992 09:40 | 42 |
| Donald L. Savage
Headquarters, Washington, D.C. December 11, 1992
Franklin O'Donnell
Jet Propulsion Laboratory, Pasadena, Calif.
RELEASE: 92-222
NASA's Cassini mission to Saturn has passed a major milestone with the
completion this week of a project-wide critical design review.
The review, which included a comprehensive examination of the mission and
spacecraft, closed today at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"We are very pleased with the outcome of the review and the status of all
elements of the project," said Richard J. Spehalski, Cassini Project Manager at
JPL. "The design process is moving forward very briskly."
In addition to JPL Cassini team members, the review included presentations
by Dr. Hamid Hassan, European Space Agency Project Manager for Cassini's
Huygens Titan probe and Dr. Romeo Pernice of the Italian Space Agency which is
contributing Cassini's high-gain antenna and science instrumentation.
In other recent activities related to Cassini, NASA issued letters to
scientific investigators formally confirming the mission's experiment payload.
The 12 experiments onboard the Cassini orbiter were tentatively selected
in 1990, subject to evaluation during an "accommodation period" until the
confirmation was issued. Another six experiments are on ESA's Huygens probe.
Planned for launch on a Titan IV-Centaur in October 1997, Cassini will fly
by Venus twice as well as by Earth and Jupiter before arriving at Saturn in
November 2004 to begin a 4-year orbital tour of the ringed planet and its 18
moons. The Huygens probe will descend to the surface of one of the moons,
Titan, in June 2005.
JPL manages the Cassini mission for NASA's Office of Space Science and
Applications, Washington, D.C.
Source:NASA Spacelink Modem:205-895-0028 Internet:192.149.89.61
|
| 640.22 | Why CASSINI may not visit any planetoids | VERGA::KLAES | I, Robot | Wed Dec 16 1992 13:30 | 35 |
| Article: 29799
Newsgroups: sci.space,sci.astro,alt.sci.planetary
From: [email protected] (Steve Flanagan)
Subject: Re: No asteroid flybys (was Re: Cassini Undergoes Intense Design
Review)
Sender: [email protected]
Organization: Jet Propulsion Laboratory
Date: Tue, 15 Dec 1992 16:35:54 GMT
[email protected] (Richard A. Schumacher) writes:
>>Nope. It was announced in *Aviation Leak* that the policy of seeking
>>asteroid flybys has been dropped to keep costs down on Cassini. :-(
>Swell. WIth our luck the damn thing will probably wind up colliding
>with an asteroid, which collision would have been recognized had
>we but continued the search for flyby possibilities...
Actually, one of the main reasons for dropping the asteroid flyby for
Cassini is that there really aren't any good flyby opportunities for
the baseline trajectory. The best we could come up with was a 22 km/s
flyby of asteroid 1987 SJ4. This is due to the fact that the only
time Cassini enters the asteroid belt is on the Earth to Jupiter leg
of the trajectory. This leg follows the "double gravity assist", the
fast (8 week) transfer from Venus to Earth, which dramatically
increases the spacecrafts heliocentric velocity. As a result,
Cassini's velocity relative to *any* main belt asteroid is going to be
very high, which makes the flyby less attractive scientifically and
more challenging operationally.
Steve Flanagan
Cassini Mission Design Team
[email protected]
Standard disclaimers apply.
|
| 640.23 | CASSINI will be the next U.S. Venus explorer | VERGA::KLAES | I, Robot | Wed Jan 20 1993 16:38 | 29 |
| Article: 55318
From: [email protected] (Ron Baalke)
Newsgroups: sci.space
Subject: Re: Next unmanned missions to Venus?
Date: 20 Jan 1993 05:55 UT
Organization: Jet Propulsion Laboratory
In article <[email protected]>, [email protected]
(rabjab) writes...
>Does anyone know of plans for future Venus exploration? Any
>leads would be appreciated.
The only mission I'm aware of that will be going to Venus within the
next 10 years is Cassini. Cassini will be making two Venus flybys in
1998 and 1999 as part of its gravity assisted trajectory to Saturn.
But other than that, it looks pretty bleak for Venus missions. I know
several members of the Magellan team would like to see another
spacecraft dedicated to Venus. The Soviets had tentative plans a
couple of years ago to send a Venera spacecraft to Venus in 2005, but
as far as I know those plans have been abandoned.
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Every once in a while,
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | try pushing your luck.
|_____|/ |_|/ |_____|/ |
|
| 640.24 | Cassini Fact Sheet -- 02/15/93 | PONIL::J_BUTLER | E pur, si muove... | Tue Feb 16 1993 13:34 | 401 |
| Article 3085 of sci.space.news:
Newsgroups: sci.space.news
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From: [email protected] (Ron Baalke)
Subject: Cassini Fact Sheet
Message-ID: <[email protected]>
To: [email protected]
Followup-To: sci.space
News-Software: VAX/VMS VNEWS 1.41
Keywords: Cassini, JPL
Sender: [email protected]
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FACT SHEET: THE CASSINI MISSION
February 15, 1993
Circled by distinctive rings and attended by a coterie of a
dozen and a half moons, Saturn has been called one of the most
intriguing planetary realms in the solar system. Its largest
moon, Titan, boasts organic chemistry that may hold clues to how
life formed on the primitive Earth.
Saturn and Titan will be the destination for the Cassini
mission, a project under joint development by NASA, the European
Space Agency and the Italian Space Agency. The U.S. portion of
the mission is managed for NASA by the Jet Propulsion Laboratory.
After arriving at the ringed planet, the Cassini orbiter
will release a probe, called Huygens, which will descend to the
surface of Titan. The Cassini orbiter will then continue on a
mission of at least four years in orbit around Saturn.
MISSION PROFILE
Launched in October 1997 on a Titan IV-Centaur rocket from
Cape Canaveral, Florida, Cassini will first execute two gravity-
assist flybys of Venus, then one each of the Earth and Jupiter to
send it on to arrive at Saturn in June 2004.
Upon reaching Saturn, Cassini will swing close to the planet
-- to an altitude only one-sixth the diameter of Saturn itself --
to begin the first of some five dozen orbits during the rest of
its four-year mission.
In late 2004, Cassini will release the European-built
Huygens probe for its descent of up to two and a half hours
through Titan's dense atmosphere. The instrument-laden probe
will beam its findings to the Cassini orbiter to be stored and
finally relayed to Earth.
During the course of the Cassini orbiter's mission, it will
execute some three dozen close flybys of particular bodies of
interest -- including more than 30 encounters of Titan and at
least four of selected icy satellites of greatest interest. In
addition, the orbiter will make at least two dozen more distant
flybys of the Saturnian moons. Cassini's orbits will also allow
it to study Saturn's polar regions in addition to the planet's
equatorial zone.
Throughout the mission, costs will be contained and
efficiency enhanced by streamlined operations. The Cassini
Project uses simplified organizational groups to make decisions;
flight controllers will take advantage of high-level building
blocks of spacecraft action sequences to carry out mission
activities.
SATURN SCIENCE
"I do not know what to say in a case so surprising, so
unlooked for and so novel," Galileo Galilei wrote in 1612. The
source of the Italian astronomer's astonishment: Only two years
after he discovered them, the rings of Saturn vanished before his
eyes.
Not that Galileo, however, recognized the rings for what
they were when he first sighted them in 1610. Having recently
discovered Jupiter's major moons, he assumed that what he saw
next to Saturn were two sizable companions close to the planet.
Two years later, however, they abruptly disappeared. In a few
more years, they mysteriously returned, larger than ever.
Galileo concluded that what he saw were some sort of "arms" that
grew and disappeared for unknown reasons.
Nearly half a century later, the Dutch scientist Christiaan
Huygens solved the puzzle that vexed Galileo. Thanks to better
optics, Huygens was able to pronounce in 1659 that the companions
or arms decorating Saturn were in fact a set of rings. The rings
were tilted so that, as Saturn orbited the Sun every 29 years,
the sheet of rings would occasionally seem to vanish as viewed
on-edge from Earth.
While observing Saturn, Huygens also discovered the moon
Titan. A few years later, the French-Italian astronomer Jean-
Dominique Cassini added several other key Saturn discoveries.
Using new telescopes, Cassini discovered Saturn's four other
major moons -- Iapetus, Rhea, Tethys, and Dione. In 1675, he
discovered that Saturn's rings are split largely into two parts
by a narrow gap -- known since as the "Cassini Division."
We now know that Saturn is one of four giant gaseous (and
ringed) planets in the solar system, joined by Jupiter, Uranus,
and Neptune. Second in size only to Jupiter, Saturn is nearly
ten times the diameter of Earth and its volume would enclose more
than 750 Earths. Even so, its mass is only 95 times that of
Earth; with a density less than that of water, it would float in
an ocean if there were one big enough to hold it.
Unlike rocky inner planets such as Earth, Saturn and the
other gas giants have no surface on which to land. A spacecraft
pilot foolhardy enough to descend into its atmosphere would
simply find the surrounding gases becoming denser and denser, the
temperature progressively hotter; eventually the craft would be
crushed and melted.
A large, modern telescope will reveal Saturn banded in pale
yellow and gray; photos from the Voyager 1 and 2 spacecraft that
flew by Saturn in the early 1980s showed even more detail in the
cloud tops of its upper atmosphere. Its neighbor Jupiter runs
toward reds, whereas the more remote Uranus and Neptune are
shades of blue.
Why the distinctive colors? The answer, in part, is because
of how far each planet is from the Sun. This in turn determines
the temperature, which decides which chemicals will be gases,
fluids or ices. At Saturn -- some 10 times more distant from the
Sun than the Earth is -- the temperature is about -180 C (-290
F). In addition to two primary, colorless gases -- hydrogen and
helium -- ammonia is relatively plentiful in the planet's upper
atmosphere. We do not understand fully, however, the source of
the colors in Saturn's clouds -- an issue that the Cassini
mission may well resolve.
The Rings
Although the best telescopes on Earth show three nested main
rings about Saturn, we now know that the ring system is a
breathtaking collection of thousands of ringlets. They are not
solid but rather are made up of countless unconnected particles,
ranging in size from nearly invisible dust to icebergs the size
of a house. The spacing and width of the ringlets are
orchestrated by gravitational tugs from a retinue of orbiting
moons and moonlets, some near ring edges but most far beyond the
outermost main rings. Instruments tell us that the rings contain
water ice, which may cover rocky particles.
There are ghostly "spokes" in the rings that flicker on and
off. What causes them? Scientists believe they may be
electrically charged particles, but we do not really know. Where
do the subtle colors in Saturn's rings come from? We cannot say;
the Cassini mission may well provide the answer.
And what is the origin of the rings themselves? One theory
is that they are the shattered debris of moons broken apart by
repeated meteorite impacts. Another theory is that the rings are
leftover material that never formed into larger bodies when
Saturn and its moons condensed. Scientists believe that Saturn's
ring system may even serve as a partial model for the disc of gas
and dust from which all the planets formed about the early Sun.
The Cassini mission will undoubtedly give us important clues.
Mysterious Moons
Saturn has the most extensive system of moons of any planet
in the solar system -- ranging in diameter from about 20
kilometers (12 miles) to 2,575 kilometers (1,600 miles), larger
than the planet Mercury. Most are icy worlds heavily studded
with craters caused by impacts very long ago.
The moon Enceladus, however, poses a mystery. Although
covered with water ice like Saturn's other moons, it displays an
abnormally smooth surface; there are very few impact craters on
the portions seen by Voyager. Has much of the surface of
Enceladus recently melted to erase craters? Could the moon also
contain ice volcanoes that provide particles for Saturn's most
distant faint ring beyond the three main rings?
Saturn's moon Iapetus is equally enigmatic. On one side --
the trailing side in its orbit -- Iapetus is one of the brightest
objects in the solar system, while its leading side is one of the
darkest. Scientists surmise that the bright side is water ice
and the dark side is an organic material of some kind. But how
the dark material got there is a mystery. Did it rise up from
the inside of the moon, or was it deposited from the outside?
The puzzle is compounded by the fact that the dividing line
between the two sides is inexplicably sharp.
Titan
But by far the most intriguing natural satellite of Saturn
is its largest. Titan lies hidden beneath an opaque atmosphere
more than fifty percent denser than Earth's. Titan has two major
components of Earth's atmosphere -- nitrogen and oxygen -- but
the oxygen is likely frozen as water ice within the body of the
moon. If Titan received more sunlight, its atmosphere might more
nearly resemble that of a primitive Earth.
What fascinates scientists about Titan's atmosphere is that
it is filled with a brownish orange haze made of complex organic
molecules, falling from the sky to the surface. Thus in many
ways it may be a chemical factory like the primordial Earth.
Most scientists agree that conditions on Titan are too cold
for life to have evolved -- although the most daring speculate
about the possibility of lifeforms in covered lakes of liquid
hydrocarbons warmed by the planet's internal heat. Yet even if
Titan proves to be lifeless, as expected, understanding chemical
interactions on the distant moon may help us understand better
the chemistry of the early Earth -- and how we came to be.
THE CASSINI SPACECRAFT
The Cassini orbiter weighs a total of 2,150 kilograms (4,750
pounds); after attaching the 350-kilogram Huygens probe and
loading propellants, the spacecraft weight at launch is 5,630
kilograms (12,410 pounds). Because of the very dim sunlight at
Saturn's orbit, solar arrays are not feasible and power is
supplied by a set of radioisotope thermoelectric generators,
which use heat from the natural decay of plutonium to generate
electricity to run Cassini. These power generators are of the
same design as those used on the Galileo and Ulysses missions.
Equipment for a total of twelve science experiments is
carried onboard the Cassini orbiter. Another six fly on the
Huygens Titan probe, which will detach from the orbiter some four
to five months after arrival at Saturn.
The Cassini orbiter advances and extends the United States'
technology base with several innovations in engineering and
information systems. Whereas previous planetary spacecraft used
onboard tape recorders, Cassini pioneers a new solid-state data
recorder with no moving parts. The recorder will be used in more
than twenty other missions both within and outside NASA.
Similarly, the main onboard computer that directs operations
of the orbiter uses a novel design drawing on new families of
electronic chips. Among them are very high-speed integrated
circuit (VHSIC) chips developed under a U.S. government-industry
research and development initiative. Also part of the computer
are powerful new application-specific integrated circuit (ASIC)
parts; each component replaces a hundred or more traditional
chips.
Elsewhere on the Cassini orbiter, the power system benefits
from an innovative solid-state power switch being developed from
the mission. This switch will eliminate rapid fluctuations
called transients that usually occur with conventional power
switches, with a significantly improved component lifetime.
Huygens Titan Probe
The Huygens probe, supplied by the European Space Agency,
carries a well-equipped robotic laboratory that it will use to
scrutinize the clouds, atmosphere, and surface of Saturn's moon
Titan.
Released by the Cassini orbiter in late 2004, the Huygens
probe will drop into Titan's atmosphere some three weeks later.
As the 2.7-meter-diameter (8.9-foot) probe enters the atmosphere
it will begin taking measurements in the haze layer above the
cloud tops. As it descends -- first on a main parachute and
later on a drogue chute for stability -- various instruments will
measure the temperature, pressure, density, and energy balance in
the atmosphere.
As the Huygens probe breaks through the cloud deck, a camera
will capture pictures of the Titan panorama. Instruments will
also be used to study properties of Titan's surface remotely --
and perhaps directly, should the probe survive the landing.
Many scientists theorize that Titan may be covered by lakes
or oceans of methane or ethane, so the Huygens probe is designed
to function even if it lands in liquid. If the battery-powered
probe survives its landing, it will relay measurements from
Titan's surface until the Cassini orbiter flies beyond the
horizon and out of radio contact.
Cassini Orbiter Experiments
-- Imaging science subsystem: Takes pictures in visible,
near-ultraviolet, and near-infrared light.
-- Cassini radar: Maps surface of Titan using radar imager
to pierce veil of haze. Also used to measure heights of surface
features.
-- Radio science subsystem: Searches for gravitational
waves in the universe; studies the atmosphere, rings, and gravity
fields of Saturn and its moons by measuring telltale changes in
radio waves sent from the spacecraft.
-- Ion and neutral mass spectrometer: Examines neutral and
charged particles near Titan, Saturn, and the icy satellites to
learn more about their extended atmospheres and ionospheres.
-- Visual and infrared mapping spectrometer: Identifies the
chemical composition of the the surfaces, atmospheres, and rings
of Saturn and its moons by measuring colors of visible light and
infrared energy given off by them.
-- Composite infrared spectrometer: Measures infrared
energy from the surfaces, atmospheres, and rings of Saturn and
its moons to study their temperature and composition.
-- Cosmic dust analyzer: Studies ice and dust grains in and
near the Saturn system.
-- Radio and plasma wave science: Investigates plasma waves
(generated by ionized gases flowing out from the Sun or orbiting
Saturn), natural emissions of radio energy, and dust.
-- Cassini plasma spectrometer: Explores plasma (highly
ionized gas) within and near Saturn's magnetic field.
-- Ultraviolet imaging spectrograph: Measures ultraviolet
energy from atmospheres and rings to study their structure,
chemistry, and compositon.
-- Magnetospheric imaging instrument: Images Saturn's
magnetosphere and measures interactions between the magnetosphere
and the solar wind, a flow of ionized gases streaming out from
the Sun.
-- Dual technique magnetometer: Describes Saturn's magnetic
field and its interactions with the solar wind, the rings, and
the moons of Saturn.
Huygens Probe Experiments
-- Descent imager and spectral radiometer: Makes images and
measures temperatures of particles in Titan's atmosphere and on
Titan's surface.
-- Huygens atmospheric structure instrument: Explores the
structure and physical properties of Titan's atmosphere.
-- Gas chromatograph and mass spectrometer: Measures the
chemical composition of gases and suspended particles in Titan's
atmosphere.
-- Aerosol collector pyrolyzer: Examines clouds and
suspended particles in Titan's atmosphere.
-- Surface science package: Investigates the physical
properties of Titan's surface.
-- Doppler wind experiment: Studies Titan's winds from
their effect on the probe during its descent.
THE INTERNATIONAL TEAM
Hundreds of scientists and engineers from 14 European
countries and 32 states of the United States make up the team
designing, fabricating and flying the Cassini-Huygens spacecraft.
In the United States the mission is managed by NASA's Jet
Propulsion Laboratory in Pasadena, California, where the Cassini
orbiter is also being designed and assembled.
Development of the Huygens Titan probe is managed by the
European Space Technology and Research Center (ESTEC). ESTEC
will use a prime contractor in southern France, with equipment
supplied by many European countries; the batteries and two
scientific instruments will come from the United States.
The Italian Space Agency is contributing the Cassini
orbiter's dish-shaped high-gain antenna as well as significant
portions of three science instruments.
Communications with Cassini during the mission will be
carried out through stations of NASA's Deep Space Network in
California, Spain, and Australia. Data from the Huygens probe
will be received at an operations complex in Darmstadt, Germany.
At JPL, Richard J. Spehalski is Cassini project manager.
Dr. Dennis Matson is Cassini project scientist.
#####
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ M/S 525-3684 Telos | If you don't stand for
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | something, you'll fall
|_____|/ |_|/ |_____|/ | for anything.
|
| 640.25 | GIF images of CASSINI, etc. | VERGA::KLAES | Life, the Universe, and Everything | Tue Feb 23 1993 15:41 | 155 |
| From: DECWRL::"[email protected]" "Ron Baalke" 21-FEB-1993
18:42:02.95
To: [email protected]
CC:
Subj: JPL GIF Images Available
==========================
JPL GIF IMAGES
February 21, 1993
==========================
I've placed some more GIF images at the Ames site. These images are
courtesy of the Public Information Office at JPL. Note that the images are
in GIF89a format, so make sure your display software supports this format
(as opposed to the older GIF87a format). The caption files accompanying
the images are appended at the end of this message, as well as being embedded
in the images. The images are available using anonymous ftp to:
ftp: ames.arc.nasa.gov (128.102.18.3)
user: anonymous
cd: pub/SPACE/GIF
files:
cassini.gif - Artists rendering of the Cassini spacecraft.
cassini.txt - Caption file.
exlaunch.gif - Explorer 1 Launch (1958)
exlaunch.txt - Caption file.
explorer.gif - Explorer 1 spacecaft.
explorer.txt - Caption file.
redspot.gif - Color image of Jupiter's red spot.
redspot.txt - Caption file.
saturn.gif - Color image of Saturn
saturn.txt - Caption file.
Also, photographic prints of these images can be ordered from
Newell Color Lab listed below. Refer to the P number associated with
the images when ordering.
Newell Color Lab
221 N. Westmoreland Avenue
Los Angeles CA 90064
Telephone: (213) 380-2980
FAX: (213) 739-6984
------------------------------------------------------------------------
cassini.txt
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
PHOTO CAPTION P-41589
February 1993
This artist's rendering depicts the NASA/JPL Cassini spacecraft
in orbit around ringed Saturn (lower right background). At the
lower left, the European Space Agency's Huygens probe descends to
the surface of Saturn's moon Titan (in foreground). Cassini is
planned for launch on a Titan IV rocket in October 1997, with
Saturn arrival in June 2004.
------------------------------------------------------------------------
exlaunch.txt
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 911O9. TELEPHONE (818) 354-5O11
PHOTO CAPTION 293-3466
This Jupiter-C rocket launch in 1958 carried into orbit the first
U.S. satellite, the Jet Propulsion Laboratory-built Explorer 1.
Sixty-six days after receiving approval to begin the project, JPL
had designed and built the 14-kilogram (31-pound) satellite.
Launch took place from Cape Canaveral Air Force Station in
Florida at 10:48 p.m. Eastern Standard Time on January 31, 1958.
In orbit Explorer 1 discovered a radiation belt around Earth
which was identified by Dr. James A. Van Allen of the University
of Iowa. Explorer 1 stopped transmitting on February 28, 1958
and reentered the atmosphere in 1970.
------------------------------------------------------------------------
explorer.txt
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 911O9. TELEPHONE (818) 354-5O11
PHOTO CAPTION P-2351Ac
Explorer 1 became the first United States satellite in space when
it was launched in 1958. Sixty-six days after receiving approval
to begin the project, the Jet Propulsion Laboratory had designed
and built the 14-kilogram (31-pound) satellite. It was launched
by a Jupiter-C rocket from Cape Canaveral Air Force Station in
Florida at 10:48 p.m. Eastern Standard Time on January 31, 1958.
In orbit Explorer 1 discovered a radiation belt around Earth
which was identified by Dr. James A. Van Allen of the University
of Iowa. Explorer 1 stopped transmitting on February 28, 1958
and reentered the atmosphere in 1970.
------------------------------------------------------------------------
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
PHOTO CAPTION P-21151
Feb. 25, 1979
This dramatic view of Jupiter's Great Red Spot and its
surroundings was obtained by Voyager 1 on Feb. 25, 1979, when the
spacecraft was 5.7 million miles (9.2 million kilometers) from
Jupiter. Cloud details as small as 100 miles (160 kilometers)
across can be seen here. The colorful, wavy cloud pattern to the
left of the Red Spot is a region of extraordinarily complex end
variable wave motion. The Jet Propulsion Laboratory manages the
Voyager mission for NASA's Office of Space Science and
Applications. This image was converted directly from digital
data to GIF format.
------------------------------------------------------------------------
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (2l3) 354-5011
PHOTO CAPTION Aug. 13, 1981
P-23883C/BW
S-2-5
NASA's Voyager 2 took this photograph of Saturn on July 21, 1981,
when the spacecraft was 33.9 million kilometers (21 million
miles) from the planet. Two bright, presumably convective cloud
patterns are visible in the mid-northern hemisphere and several
dark spoke-like features can be seen in the broad B-ring (left of
planet). The moons Rhea and dione appear as blue dots to the
south and southeast of Saturn, respectively. Voyager 2 made its
closest approach to Saturn on Aug. 25, 1981. The Voyager project
is managed for NASA by the Jet Propulsion Laboratory, Pasadena,
Calif. This image was converted directly from digital data to
GIF format.
#####
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ M/S 525-3684 Telos | If you don't stand for
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | something, you'll fall
|_____|/ |_|/ |_____|/ | for anything.
|
| 640.26 | CASSINI Titan Radar Mapper | VERGA::KLAES | Life, the Universe, and Everything | Tue Mar 30 1993 18:17 | 39 |
| Article: 59999
From: [email protected] (Steve Derry)
Newsgroups: sci.space
Subject: Re: Question on Cassini Radar
Date: 29 Mar 93 20:44:35 GMT
Organization: NASA Langley Research Center, Hampton, VA USA
The June 91 issue of Proceedings of the IEEE (vol 79, no 6) has an
article describing the Cassini Titan Radar Mapper. All details in
this posting are from that article, which was written when Cassini was
still scheduled for a 1995 launch.
The baseline Cassini mission calls for 59 orbits of Saturn, 35 of
which will make a close flyby of Titan. 29 of these will approach to
within 4000 km, with 15 of these approaching as low as 950-1100 km.
Each Titan pass will provide an opportunity for about 32 minutes of
radar operation yielding 1.5% coverage of Titan's surface per pass.
Although the article didn't discuss total coverage for the mission,
there will be some overlap of coverage between passes, so the total
coverage will be less than 50%.
The radar itself will operate at 13.8 GHz, using the same 3.66m HGA
that is used for telecom (ala Magellan). The radar will emit a
multi-beam pattern that allows coverage of both sides of the ground
track on a single pass. The radar operates in 3 resolution modes
(depending on the altitude), with resol- utions ranging from 400m to
1.6km. One interesting complication is that the uncertainties in the
spacecraft ephemeris and attitude during the flyby's lead to some
pointing uncertainty during radar operation. The plan is to acquire
the radar imagery in an unfocused SAR mode, and then do precise geo-
coding with a high-accuracy ephemeris which can be obtained from
post-encounter analysis.
In addition to SAR imaging, the radar will be operated in an
altimeter/ scatterometer mode.
--
Steve Derry
<[email protected]>
|
| 640.27 | RE 640.26 | VERGA::KLAES | Life, the Universe, and Everything | Thu Apr 01 1993 13:46 | 100 |
| Article: 60104
Newsgroups: sci.space
From: [email protected] (David Seal)
Subject: Re: Question on Cassini Radar
Sender: [email protected]
Organization: Jet Propulsion Laboratory
Date: Tue, 30 Mar 1993 19:53:47 GMT
[email protected] (Bill Higgins-- Beam Jockey) writes:
>In article <[email protected]>, [email protected] (Schroder S) writes:
>> This is a request for more information about the Cassini radar.
>I wonder whether they have any plans to point it at Saturn. Would it
>show anything? And will they use the radar on other satellites which
>are not cloudy?
That's a neat question. For now we are not planning to point it at
anything except Titan. The orbit period(s) are designed to by
synchronous with Titan's (i.e. n orbits of the spacecraft with every m
orbits of Titan, where n and m are integers, usually) so targeted icy
satellite flybys are much less numerous. We have a requirement to
provide at least four, and have a number of nontargeted encounters,
but those are easily too far away to provide good radar data. And
since the targeted icy satellite flybys are so few, we will be doing
remote sensing during that period.
>You are correct. The SAR will scan only a few skinny little strips of
>Titan's surface. Cassini will not orbit Titan, so the radar can only
>be used on a few occasions when its Kronian orbit (I saw this word in an
>astronomy paper the other day, I couldn't wait to use it) brings it
>close to Titan. It will still be better than pictures of a
>featureless orange tennis ball!
There's some speculation that we might be able to see down to Titan's
surface with the remote sensing instruments, as well as with radar.
The Voyager images were confined to relatively narrow frequencies, and
it's possible that the surface might be visible at others. We all
hope we get a lot better than the tennis ball we have now.
Dave Seal
Cassini Mission Design
--
-----------------------------------------------------------------------------
David Seal | Jet Propulsion Laboratory | sunset: 7:54pm
[email protected] | Mission Design | temp: 82 degrees
Article: 60124
From: [email protected] (Steve Derry)
Newsgroups: sci.space
Subject: Re: Question on Cassini Radar
Date: 31 Mar 1993 04:15:17 GMT
Organization: NASA Langley Research Center, Hampton, VA USA
David Seal ([email protected]) wrote:
: That's a neat question. For now we are not planning to point it at anything
: except Titan.
Would the radar be of any benefit in trying to characterize Saturn's rings?
I.e. distributions of particle (or boulder?) size, etc?
--
Steve Derry
<[email protected]>
Article: 60150
From: [email protected] (Bill Higgins-- Beam Jockey)
Newsgroups: sci.space
Subject: Re: Question on Cassini Radar
Date: 31 Mar 93 10:09:42 -0600
Organization: Fermi National Accelerator Laboratory
In article <[email protected]>, [email protected] (Steve
Derry) writes:
> David Seal ([email protected]) wrote:
> : That's a neat question. For now we are not planning to point it at anything
> : except Titan.
>
> Would the radar be of any benefit in trying to characterize Saturn's rings?
> I.e. distributions of particle (or boulder?) size, etc?
If I may speculate here (David can give us the *correct* answer),
radar would be useful, in principle, for looking at the rings, but
Cassini will not get close enough to the rings to use it. Recall
that this is true for the surfaces of moons as well, other than Titan.
The performance of radar is limited in range and Cassini's must be
rather close to its targets, within a few thousand kilometers.
--
O~~* /_) ' / / /_/ ' , , ' ,_ _ \|/
- ~ -~~~~~~~~~~~/_) / / / / / / (_) (_) / / / _\~~~~~~~~~~~zap!
/ \ (_) (_) / | \
| | Bill Higgins Fermi National Accelerator Laboratory
\ / Bitnet: [email protected]
- - Internet: [email protected]
~ SPAN/Hepnet: 43011::HIGGINS
|
| 640.28 | JPL and TRW to develop X-SSPA | VERGA::KLAES | Life, the Universe, and Everything | Sat May 29 1993 16:37 | 54 |
| Article: 3827
Newsgroups: sci.space.news
From: [email protected] (Ron Baalke)
Subject: JPL, TRW Will Develop Cassini Power Amplifier
Sender: [email protected]
Organization: Jet Propulsion Laboratory
Date: Sat, 29 May 1993 03:02:00 GMT
From the "JPL Universe"
May 21, 1993
Lab, TRW will jointly develop Cassini power amplifier
JPL and TRW have signed a cooperative agreement to develop a
Cassini X-band Solid State Power Amplifier (X-SSPA) as a potential
backup for the current baseline Traveling Wave Tube Amplifier, which
will amplify signals for data transmission from the Cassini spacecraft
to Earth, said Steve Burkhart of the Spacecraft Telecommunications
Equipment Section 336.
TRW is responsible for the design of the microwave amplifiers and
packaging of the unit; JPL will support the development activity and
perform the necessary life testing to space-qualify the output power
amplifier devices provided by Avantek, a Hewlett-Packard subsidiary
and another partner in the project.
"Although a flight X-SSPA contract from JPL cannot be
guaranteed," Burkhart said, "both TRW and Avantek will benefit from
this cooperative effort. Currently, there are no space-qualified
high-efficiency output power amplifier devices that operate in the
8GHz frequency band, and the space qualification testing at JPL will
provide industry with qualified devices that could be utilized in
either in JPL missions or other space programs that require X-band
SSPAs.
"TRW is just one example of a company that can benefit from
having a space-qualified X-band power device resulting from this
cooperative effort with JPL, and Avantek may also benefit from the
agreement as new markets open up for its space-qualified devices,"
Burkhart said.
The joint effort was initiated by Cassini Spacecraft Manager Tom
Gavin, who worked with Section 336 and the Technology Affiliates
Office, Section 893, under Jim Rooney. There is no exchange of funds
under this cooperative agreement; JPL's work will be funded by the
Cassini project, while TRW will provide its own funding sources.
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Never laugh at anyone's
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | dreams.
|_____|/ |_|/ |_____|/ |
|
| 640.29 | The parameters of HUYGENS | VERGA::KLAES | Quo vadimus? | Mon Aug 23 1993 09:57 | 146 |
| Article: 69792
From: [email protected] (R.D.Lorenz)
Newsgroups: sci.space
Subject: Cassini/Huygens delivery
Date: 20 Aug 93 16:03:18
Organization: Computing Lab, University of Kent at Canterbury, UK.
In Article: 64385 of sci.space
[email protected] (Marcus Lindroos INF) writes
>Subject: Cassini/Huygens - why brake entire craft?
> A question about the proposed Cassini mission to Saturn: why will the
>Huygens atmospheric probe be released *AFTER* the mothership has entered orbit
>
>around the planet?! Wouldn't it make more sense to detach Huygens a
>couple of weeks before arrival and have it enter Titan's atmosphere without
>assistance from the orbiter, thus saving valuable propellant... Or would
>there be problems with data transmission (Cassini probably wouldn't be able to
>achieve a close flyby of of Titan before entering orbit around Saturn), and
>would Huygens have to be equipped with a heavier heat shield as its speed when
>entering Titan's atmosphere certainly would be higher...?
---
> Too bad we can't land a long-life lander on Titan. I'd love to have a Viking
>style probe relay data from the surface, could survive there for years.
There are several factors
1. As you point out, entry loads would be considerably higher as a
result of the increased entry velocity, requiring more thermal protection
2. Communications from Titan are relayed via the orbiter - so a major
constraint on mission duration (atmospheric descent + any surface
mission) is the availability of the orbiter above the horizon: on the
arrival orbit, the orbiter craft will be travelling much faster, so
would have a much shorter time to relay probe signals. (Unless it used
loads of fuel to delay it's approach, but then the comms distance is
higher, so the data rate is lower, etc.)
3. I suspect that the delivery errors from a pre-arrival release would
be intolerably high.
As for long-life lander on the surface - that's for after
Cassini/Huygens, I think - when we know how much of the surface is
liquid and how much is solid.
Just out of interest - why would you 'love to have a Viking-style'
probe on the surface for years - if you were lucky, there might be
some nice meterology to see, maybe even some seismic activity, but
that's about it?
NB the problems of a long-duration vehicle (balloon, rover, submarine
or whatever) on Titan are non-trivial: I have done some studies and
seen others - to name two problems, communications without a relay are
difficult, and the 94K surface temperature (+thick atmosphere) is
challenging from a thermal design point of view : yes, you can put
RHUs/RTGs in the probe, and insulate it nicely, but then you have to
think how to reject that heat from inside the probe during the long
interplanetary cruise. Not an easy problem.
Ralph Lorenz
Unit for Space Sciences
University of Kent
(co-Chairman - Huygens Surface Mission Group)
------------------------------
Date: Fri, 20 Aug 1993 20:59:42 GMT
From: David Seal <[email protected]>
Subject: Cassini/Huygens delivery
Newsgroups: sci.space
In <[email protected]> [email protected] (R.D.Lorenz) writes:
>In Article: 64385 of sci.space
>[email protected] (Marcus Lindroos INF) writes
>> A question about the proposed Cassini mission to Saturn: why will
>> the Huygens atmospheric probe be released *AFTER* the mothership has
>> entered orbit
>3. I suspect that the delivery errors from a pre-arrival release would be
>intolerably high.
I would tend to doubt that delivery errors would be substantially
effected, as they tend to result from inexact separation, solar
radiation torques, and other environmental disturbances which wouldn't
be much affected by higher incoming velocities. As it is, the probe
is being released 22 days before entry and the error ellipse is still
only about 38km x 230 km in size. All of your other responses were
consistent with what i know of the project's position.
dave
--
-----------------------------------------------------------------------------
David Seal | Jet Propulsion Laboratory | sunset: 7:54pm
[email protected] | Mission Design | temp: 82 degrees
------------------------------
Date: 21 Aug 93 13:05:22
From: "R.D.Lorenz" <[email protected]>
Subject: Cassini Delivery
Newsgroups: sci.space
In Article: 64469 of sci.space, Dave Seal ([email protected]) writes
>I would tend to doubt that delivery errors would be substantially effected,
>as they tend to result from inexact separation, solar radiation torques,
>and other environmental disturbances which wouldn't be much affected by
>higher incoming velocities. As it is, the probe is being released 22 days
>before entry and the error ellipse is still only about 38km x 230 km in size.
I was under the impression delivery errors were dominated by imprecise
separation, and more particularly by uncertainties in the Titan
ephemeris (I was surprised too) I would guess solar radiation pressure
is pretty negligible at 9.5AU. (You say 'torques' - N.B. the attitude
of the probe does not drive the delivery error.)
Surely in order to achieve an adequate orbiter delay time to perform
the Probe mission, the Orbiter Delay Manoeuvre (ODM) must still be
performed something like 20 days prior to arrival, so the coast phase
of the probe mission must still last about 22 days, as in the 'real'
Cassini mission. The difference with pre-arrival delivery is that this
22 days equates to a much greater distance, and hence greater scope
for relative position errors.
>All of your other responses were consistent with what i know of the project's
>position.
I hope so :-)
After checking up on a few diagrams (see, eg. the Cassini Phase A
report) I not e that the arrival occurs at a substantial inclination
to Saturn's equator. Thus, for a mission where the probe is delivered
on the inbound leg, the orbiter would hit the Saturn B-plane far too
far away from Saturn to achieve insertion. This, I suspect, is as
important (for the orbiter mission) as any of the other factors.
The mission planners at JPL (and at ESTEC/ESOC) do a great job on
these things. I reckon 38x230km is pretty good shooting.
Ralph Lorenz
Unit for Space Sciences
University of Kent, UK.
|
| 640.30 | Titan/CASSINI/HUYGENS References | VERGA::KLAES | Quo vadimus? | Mon Dec 13 1993 18:58 | 68 |
| Article: 79707
From: [email protected] (Counsel Wolf)
Newsgroups: sci.space
Subject: Titan & Cassini
Date: Mon, 13 Dec 93 16:11:14 GMT
Organization: University of Kent at Canterbury, UK.
Sender: [email protected]
There has been some recent discussion re: Titan and its surface,
discussion which has, alas, revealed some misconceptions, even among
otherwise reliable network contributors. Since I am completing a PhD
on the subject of the surface of Titan, perhaps I can throw some light
on this.
Titan:
General description of Titan - see Gehrels and Matthews (eds) 'Saturn'
- University of Arizona Press Burns and Matthews (eds) 'Satellites' - ditto
Cassini:
Cassini is a joint NASA/ESA mission. ESA builds the Huygens probe,
which isn't exactly small (circa 300kg - about the size of the Pioneer
Venus Large Probe)
A good summary of the Cassini mission may be found in the last-but-one
issue of The Planetary Report.
The next issue of the ESA Bulletin will contain an up-to-date pair of
articles on the mission and the probe design.
Titan's Surface:
A good recent review of Titan's surface is in Review of Geophysics v.31
p.131
Also, there is a big review article on the surface of Titan in the next
ESA Journal (probably out in Jan/Feb)
Frank Cary cited the radar measurements by Muhlemann et al - NB the
reflectivit is high, which is INCONSISTENT with a global ocean (which
would have a low reflectivity) (original paper was Science v.248 p975)
The reflectivity is apparently variable in longitude, a result which
has been confirmed by groundbased IR observations (there are some
near-IR windows where we can see through the atmospheric haze) see
Icarus v.101 p.272, Icarus v.93 p.362, Icarus v.103 p.329, Nature
v.364 p.511
HST : nothing published yet, although one image taken (Titan is about
20 pixels across). The real fun will come with WFPC-II
My best-guess is a mixed surface, with some liquid and some solid
......but we'll have to wait to 2004 to be sure, when the Huygens
probe will be delivered (NB it may survive on the surface, but it is
not, for cost and practicality reasons, being 'designed' to do so)
As well as using radar, the Cassini orbiter spacecraft will be able to
map the surface in the infrared. The Huygens probe will take plenty of
pictures from BENEATH the methane cloud deck.
Hope this helps
Ralph Lorenz
Unit for Space Sciences
University of Kent
|
| 640.31 | ROMBUS to Titan | VERGA::KLAES | Quo vadimus? | Mon Dec 13 1993 19:01 | 51 |
| Article: 79685
Newsgroups: sci.space
From: [email protected] (Marcus Lindroos INF)
Subject: Re: TITAN AND MANNED MISSIONS (you got it:-)
Sender: [email protected] (Usenet NEWS)
Organization: ABO AKADEMI UNIVERSITY, FINLAND
Date: Mon, 13 Dec 1993 07:45:55 GMT
A manned mission to Titan will become feasible once we have a reusable single
stage to orbit, heavy-lift launch vehicle capable of lifting payloads in the
400-450 ton range. My personal favorite is Philip Bono's ROMBUS - a
barrel-shaped behemoth that would have weighted 6400 tons on the launch pad.
ROMBUS was proposed in 1967, unfortuantely McDonnell Douglas never managed to
persuade NASA to fund it although the Delta Clipper has a lot in common with
Bono's original design.
---
ROMBUS would have been 35m high, with a diameter of 24 meters. The original
design would have used an aerospike engine, but if we replace this with a
couple of powerful nuclear engines, we would have a highly efficient
interplanetary cargo vessel. Inside, there is a 4200m3 spherical fuel tank (20m
diameter) and a heatshield at the bottom of the craft. The idea is to
touch down on a planetary surface, then fill the fuel tank with any suitable
gas or liquid (water, methane, carbon dioxide or whatever) and go home.
---
A ROMBUS Titan mission would begin in LEO. A fleet of three ROMBUSes powered
by ordinary chemical rockets would launch the manned payload of 300 tons
(equipment, habitat modules, spare parts, supplies) plus eight strap-on tanks
containing 900 tons of liquid hydrogen for the outward leg. That makes eight
Shuttle ET tanks - piece of cake for a launcher that is 24m wide. The total
mass in LEO would be 1,700 tons.
---
The mission to Titan would take four years, including a 1 million km flyby of
Jupiter two years after launch. The spent ET tanks are jettisoned soon after
leaving Earth orbit. Four years later, the ROMBUS craft lands on Titan using
aerobraking. Safely on the surface, the crew refuels the craft with methane
from the atmosphere - the internal tank could store almost 1,900 tons of liquid
methane. We then use the propellant for making a round trip to other moons in
the Saturnian system. Theoretically, a quick 2-year return trip to Earth would
be possible although I suspect this would be too fast for aerobraking - some of
the fuel would be needed to to slow down the ship before reentering the Earth's
atmosphere.
---
Science fiction? Perhaps, but I think we need a reusable, interplanetary
nuclear-powered "shuttle" capable of using in situ propellant if we are to
colonize the Solar system. Not necessarily a ROMBUS either, a tiny Delta
Clipper would be enough for setting up as base on the Moon/Mars. Incidentally,
this is another of Robert Zubrin's proposals. Does anyone know if the man has
got a fan club?:-)
MARCU$
|
| 640.32 | | TNPUBS::ALLEGREZZA | George Allegrezza @LKG | Wed Dec 15 1993 08:39 | 17 |
| Re: last
ROMBUS actually goes back further than 1967. Phil Bono looked at a
number of launcher designs as part of a 1960-62 NASA study on
establishing and supplying a 1000-person lunar colony. (One of the
designs studied was a nuclear SSTO with a 454-foot diameter lenticular
shape.) ROMBUS (Reusable Orbital Module -- Booster and Utility System)
was one of the more practical designs settled upon, and Bono continued
to refine it during his years at Douglas, using some funding from the
Post-Saturn and Post-Nova studies out of Marshall.
Refs:
"The ROMBUS Concept," Astronautics and Aeronautics, Jan. 1964
_Frontiers of Space_, Bono and Gaitland, (forgot the publisher, sorry),
1969
|
| 640.33 | RE 640.30 | VERGA::KLAES | Quo vadimus? | Wed Dec 15 1993 15:47 | 179 |
| Article: 79774
Newsgroups: sci.space
From: [email protected] (Frank Crary)
Subject: Re: Titan & Cassini
Sender: [email protected] (Net News Administrator)
Organization: University of Colorado, Boulder
Date: Tue, 14 Dec 1993 04:34:35 GMT
In article <[email protected]>, Counsel Wolf <[email protected]> wrote:
>.....but we'll have to wait to 2004 to be sure, when the Huygens probe will be
>delivered (NB it may survive on the surface, but it is not, for cost and
>practicality reasons, being 'designed' to do so)
A friend worked on the Phase A/B design project. At that point it was
being designed to survive a hard landing or float in methane. He stayed
in touch through the Phase C/D work, and said this was still a design
goal (although perhaps a low priority...) Has something changed since
Phase C/D? (Unusual but still possible...)
>As well as using radar, the Cassini orbiter spacecraft will be able to map the
>surface in the infrared.
What's the wavelength of the IR imager? The atmosphere and surface
would be emitting strongly in all the IR windows I can think of...
Are we going to get a clear surface map, or will we see alot of
noise from thermal emission?
>The Huygens probe will take plenty of pictures from BENEATH the methane cloud
>deck
If there is a cloud deck. There are probably clouds, but they may be
scattered... We also don't really know the altitude of the clouds.
Huygens won't be able to take many usefull pictures if there are
very low altitude clouds or fog. The important part, in my opinion
it taking pictures below the haze layer: That's high enough that
we will get surface images through holes in the clouds no matter what
the surface weather is like directly below Huygens.
By the way, what direction does Huygen's camera point? After it reaches
the surface will we get pictures of the surface or a close up of the
square centimeter of ice under the lense?
Frank Crary
CU Boulder
Article: 79793
Newsgroups: sci.space
From: [email protected] (Mike Malin)
Subject: esRe: Titan & Cassini
Sender: [email protected] (USENET News System)
Organization: Mars Observer TES Project, ASU, Tempe AZ
Date: Tue, 14 Dec 1993 03:23:32 GMT
In message <[email protected]>, Ralph Lorenz states:
"The Huygens probe will take plenty of pictures from BENEATH the
methane cloud deck."
This is a bit misleading--the available data rate from the probe is
quite low (it varies from a few 100 to several 1000 bits/sec) and the
total data volume is quite small (of order 15 Mbits). Given that the
other instruments require not insignificant amounts of that rate and
volume, even with DSIR's small detector and relatively high
compression factors (which I'm not sure DSIR can achieve under limited
power allocations) I don't believe "plenty" of pictures will be acquired.
I think the number will be, at most, several dozen, and these will be
small and, depending on scene activity, fairly low resolution.
A second point is that of visibility in the lower titanian atmosphere.
Both methane clouds and ethane aerosals may form below about 50 km.
Fogs may occur locally over standing bodies of liquid. The vertical
and horizontal distribution of these (vis a vis "decks", etc.) has, at
least as far as I know, not been established. I believe we are all
hoping that DSIR will be able to image the surface as it decends into
the lower atmosphere, but I don't think that is by all means assured.
Mike Malin
ex-Mars Observer Camera Principal Investigator
Unsuccessful Proposer of a Descent Imaging Spectrometer and Large
Format/High Resolution Camera for the Huygens Probe
Article: 79863
From: [email protected] (Counsel Wolf)
Newsgroups: sci.space
Subject: Re: esRe: Titan & Cassini
Date: Wed, 15 Dec 93 10:32:51 GMT
Organization: University of Kent at Canterbury, UK.
Sender: [email protected]
In article <[email protected]>
[email protected] (Mike Malin) writes:
>In message <[email protected]>, Ralph Lorenz states:
>"The Huygens probe will take plenty of pictures from BENEATH the
>methane cloud deck."
>
>This is a bit misleading--the available data rate from the probe is
>quite low (it varies from a few 100 to several 1000 bits/sec) and the
>total data volume is quite small (of order 15 Mbits).
Not true - in the current scenario, data rate is of the order of
8kbit/s, over 2-3 hours: The numbers you quote are probably from the
Phase A study (5 years ago?) - back when the Cassini orbiter had a
Probe Relay Antenna. Now we use the main HGA
> Given that the
>other instruments require not insignificant amounts of that rate and
>volume, even with DSIR's small detector and relatively high
>compression factors (which I'm not sure DSIR can achieve under limited
>power allocations) I don't believe "plenty" of pictures will be
>acquired. I think the number will be, at most, several dozen, and
>these will be small and, depending on scene activity, fairly low resolution.
DISR uses something like 70% of the available data rate on the probe.
I couldn't comment on the compression used.
>A second point is that of visibility in the lower titanian atmosphere.
>Both methane clouds and ethane aerosals may form below about 50 km.
Latest word is that the ethane aerosols may start 60-80km up. Methane
clouds could be from 40km downwards (I happen to have done some
research on rainfall on Titan). Voyager 1 radio-occultation data rules
out methane clouds below 3km. Interpretation of near-IR spectra
suggests that the methane clouds are either patchy, or optically thin
(see Toon et al, Methane Rain on Titan, Icarus (1988)
>Fogs may occur locally over standing bodies of liquid.
Agreed, this suggestion goes back to Lunine et al 1983. There is
another phenomenon which may occur due to the evaporation of methane
raindrops as they descend, depositing the ethane core droplets which
acted as their condesation nucleus as a thin near-surface cloud (I
call it a 'rain ghost' - The Life, Death and Afterlife of a Raindrop
on Titan, Planetary and Space Science, in press)
> The vertical
>and horizontal distribution of these (vis a vis "decks", etc.) has, at
>least as far as I know, not been established.
Also agreed: I oversimplified (not expecting so august and educated a
correspondent) for brevity's sake
> I believe we are all hoping
and expecting!
> that DSIR will be able to image the surface as it decends into
>the lower atmosphere, but I don't think that is by all means assured.
I spoke to Marty Tomasko last month in Arizona (the DISR PI) and he thinks
they may see surface contrast right from the start of descent, at 170km.
If you have such doubts about the feasibility of imaging the surface, why
did you propose a camera to do it?
Also, for what it's worth, here at Kent we are working (in
collaboration with ESTEC SSD) on a small echo-sounder for the probe -
if we can't see the ground, then we should at least know that it's
coming, and whether it is solid or liquid.
>Mike Malin
>ex-Mars Observer Camera Principal Investigator
>Unsuccessful Proposer of a Descent Imaging Spectrometer and Large
>Format/High Resolution Camera for the Huygens Probe
I hope your luck improves.
Ralph Lorenz
ex-assistant to the ESA Huygens payload engineers
hoping-to-get-my-PhD-in-7-months-or-so
Unit for Space Sciences
University of Kent
United Kingdom
|
| 640.34 | RE 640.33 | VERGA::KLAES | Quo vadimus? | Sat Dec 18 1993 13:58 | 69 |
| Article: 79924
Newsgroups: sci.space
From: [email protected] (Frank Crary)
Subject: Re: esRe: Titan & Cassini
Sender: [email protected] (Net News Administrator)
Organization: University of Colorado, Boulder
Date: Wed, 15 Dec 1993 18:21:31 GMT
In article <[email protected]>, Counsel Wolf <[email protected]> wrote:
>Not true - in the current scenario, data rate is of the order of 8kbit/s,
>over 2-3 hours : the numbers you quote are probably from the Phase A study
>(5 years ago?) - back when the Cassini orbiter had a Probe Relay Antenna.
>Now we use the main HGA
Using the HGA explains how you get 8 kbps, but how do you manage it
for several hours? I though Cassini would be below Titan's horizon and
out of contact about 30 min. after the probe entered the atmosphere.
>>A second point is that of visibility in the lower titanian atmosphere.
>>Both methane clouds and ethane aerosals may form below about 50 km.
>Latest word is that the ethane aerosols may start 60-80km up. Methane
>clouds could be from 40km downwards...
How so? I though the ethane/organic haze extended down to the cloud
tops. It's just diffusing downwards from the upper stratosphere where
it is formed. That shouldn't change until it reached the uppermost
cloud deck.
>...Voyager 1 radio-occultation data rules out methane clouds below 3km.
Er... As I understand it, the Voyager data _and_ some rather uncertain
radiative transfer modeling. According to the models, the surface
relative humitity is 50 to 60% (depending on whether you trust
McKay or Sagan more...) If that estimate is correct, the Voyager
temperature profile rules out clouds below 3 km. But the models are
1-D, globally averaged models. There is certainly going to be
local variation in the surface humidity and some regions (especially
those near methane seas) would have a humidity well over 60% and
potentially clouds well below 3 km.
>...There is another
>phenomenon which may occur due to the evaporation of methane raindrops
>as they descend, depositing the ethane core droplets which acted as their
>condesation nucleus as a thin near-surface cloud...
Shouldn't we see the same thing on Earth? We do, after all, occasionally
get rain which evaporates before reaching the surface and rain on
Earth also has a nucleus of some sort of aerosol.
By the way, you seem to be refering to ethane where I'd say haze (or
Sagan would say "tholin"). Are you just assuming that the haze
is mostly ethane, or does ethane dominate the low-altitude end
of the haze layer for some reason?
>Also, for what it's worth, here at Kent we are working (in collaboration
>with ESTEC SSD) on a small echo-sounder for the probe - if we can't see
>the ground, then we should at least know that it's coming, and whether it
>is solid or liquid
You might be able to do much more than that with an echo-sounder. There
is some possibility you could get a depth of a methane sea if the
probe lands in one. To judge by the other icy moons, the surface
contours should be small on Titan, and the sea would probably be
under 500m deep. That's well within the capability of an echo-sounder.
Frank Crary
CU Boulder
|
| 640.35 | RE 640.34 | VERGA::KLAES | Quo vadimus? | Thu Dec 23 1993 14:18 | 63 |
| Article: 80117
Newsgroups: sci.space
From: [email protected] (Mike Malin)
Subject: Re: Titan & Cassini
Sender: [email protected] (USENET News System)
Organization: Mars Observer TES Project, ASU, Tempe AZ
Date: Sat, 18 Dec 1993 23:26:00 GMT
In an earlier post, I questioned Ralph Lorenz's statement that the
descent imaging spectrometer/radiometer (DISR) on the Huygens probe
would in fact return many images, based on the data rates and volumes.
He correctly pointed out in his post <[email protected]> that I was
using rates and volumes from the proposal package, and that the data
rates were significantly higher now because the High Gain Antenna
(HGA) on the main Cassini spacecraft would be used to receive the
probe's data.
Given his familiarity with the Huygens payload and operations
scenario, it might be interesting for Ralph to post some additional
information on Huygens, specifically its total data return, the amount
allocated to each instrument, and relative to the earlier thread, the
number and format (pixel size, pixel depth, etc.) of images that may
be taken by the DISR.
During the rest of his comments, Ralph argues well for the possibility
(or he might say probability) of actually observing the surface during
descent, citing several different sources that suggest they are seeing
through the clouds and haze layers at IR wavelengths. He concludes
with the question "If you have such doubts about the feasibility of
imaging the surface, why did you propose a camera to do it?"
I remain unconvinced by the Voyager and HST observations that they are
"seeing" to the surface and, as Frank Crary notes in his recent
posting, much of the discussion of what's going on in the lower
atmosphere is based mostly on models often considerably simplified
over what might reasonably cover the range of natural phenomena.
In answer to Ralph's question, like Tomasko, I proposed a combined
imaging spectrometer and camera. The spectrometer would have
measured, several times per scale height, the wavelength-dependent
optical depth, the angular distribution of sky brightness, solar
energy as a function of altitude, and hopefully, surface albedo. From
these measurements, we would have calculated solar heating rates,
particle sizes in the atmosphere, particle concentration in the
atmosphere, optical constants of the particles, vertical transport (by
tracking the particles), vertical cloud structure, and methane mixing
ratio. The camera would have taken images of the limb (looking for
haze layers) and, looking down, of cloud tops. Once in the lower
atmosphere, the camera would have looked for rain, other forms of
clouds, fogs, and, of course, the surface. We opted for a large
format camera with lots of pixels: each image would have been 800 X
800 pixels and would have been able to resolve features 50 m across
from 20 km altitude. The images would have covered a few meters
across at resolutions of a few cm. I believe DISR takes both smaller
images and lower resolution, but perhaps Ralph can shed more light on
this.
Mike Malin
ex-Mars Observer Camera Principal Investigator
Unsuccessful Proposer of a Descent Imaging Spectrometer and Large
Format/High Resolution Camera for the Huygens Probe
|
| 640.36 | A possible return to Shuttle launches | VERGA::KLAES | Quo vadimus? | Wed Mar 02 1994 14:21 | 53 |
| Article: 917
From: [email protected] (Ron Baalke)
Newsgroups: sci.space.policy
Subject: Re: Cassini
Date: 2 Mar 1994 17:15 UT
Organization: Jet Propulsion Laboratory
In article <[email protected]>, raptor!rlove
(Robert B. Love ) writes...
>I've heard a rumor to the effect that work on Cassini is halted while
>some study on launching via Shuttle (perhaps 2 launches) has been ordered
>by Congress. This raises the following questions:
>
>1) Is the story true? Anybody have details.
There is an article on this in the latest issue of Space News. NASA
is studying the possibility of launching Cassini from the Shuttle
because of concerns that were raised when a Titan 4 failed last
August. This is only a study though, and work has not stopped on
Cassini. Launching Cassini from the Shuttle would require two
separate launches. The results of the study will be presented to Dan
Goldin in early April.
>2) Which member of Congress or committee mandated this.
The White House Office of Management and Budget.
>3) What is the rationale for putting Cassini on the Shuttle.
See answer to question 1.
>4) If pork barrel, what company/NASA Center benefits.
It is not pork barrel, just concerns over the reliability of the
launch vehicle. The costs of launching from the Shuttle seems to be
obscure though. A Titan 4 launch costs about $300 million. Shuttle
launches cost about $500 million each (according to the article) but
is justifiable because NASA will be launching 8 shuttle missions/year
regardless if Cassini is on the manifest or not.
In an interesting sidenote, the article also listed the costs of the
upper stages for Galileo and Ulysses, both of which were launched from
the Space Shuttle. The cost of the upper stage for Galileo was double
that of Ulysses ($45 million vs $87 million).
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ Galileo S-Band | Failure is success if we
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | learn from it.
|_____|/ |_|/ |_____|/ | Malcom Forbes
|
| 640.37 | International Titan radar efforts | JVERNE::KLAES | Be Here Now | Wed Mar 30 1994 15:59 | 125 |
| Article: 335
From: [email protected] (Ron Baalke)
Newsgroups: sci.space.science,sci.space.tech
Subject: Cassini's Radar Efforts
Date: 30 Mar 1994 02:44 UT
Organization: Jet Propulsion Laboratory
>From the "JPL Universe"
March 25, 1994
International cooperation noted on Cassini radar efforts
By Ed McNevin
Charting a new course of exploration for a nation known for
great explorers, four members of the Italian aerospace firm
Alenia Spazio, under contract to the Italian space agency Agenzi
Spaziale Italiana (ASI), recently concluded a two-month visit to
JPL, where they completed preliminary tests on the prototype of
the Cassini Radar instrument. Scientists hope the instrument will
uncover many of the mysteries surrounding the hidden surface of
one of Saturn's moons, Titan.
The Italian engineering test team--which included Leonardo
Borgarelli, Enrico Zampolini, Roberto Chiappi and Marco Nati
--joined JPL engineers in analyzing the mechanical and electrical
interface between a prototype of the Italian (RF Electronic
Subsystem) RFES and a prototype of the Digital Subsystem (DSS),
which will be built at JPL.
In order to send a radar signal through Cassini's radar
antenna--which is also being provided by the Italian Space
Agency--the DSS, which essentially acts as the brain of the
Cassini radar instrument, will forward a command to the RFES. The
subsystem will then direct the radar signal toward Titan. Once
the reflected signal has been received by the antenna and
receiver, the signal will then be relayed back into the DSS,
where it will be stored in the spacecraft's digital data
recorders until it is relayed back to Earth.
According to Dr. Young Park, Cassini radar project manager
at JPL, the primary goal of the Cassini Radar experiment is to
determine the characteristics of Titan's surface, which is
covered by a dense, optically opaque atmosphere, using the
imaging mode, the altimeter mode and the radiometer mode in the
Cassini radar instrument.
"Scientists are very interested in the surface on Titan, and
the major objective of the Cassini radar instrument is to reveal
the surface," Park said.
Planetary scientists have been particularly interested in
Titan since the Voyager flybys of Saturn in the early 1980s.
Scientists have yet to determine whether the surface is
liquid or solid, although it has been speculated that Titan could
be covered by large oceans of hydrocarbons, principally ethane
and methane. The Cassini radar, like Magellan's Synthetic
Aperture Radar at Venus, should uncover many of the secrets
hidden beneath the thick clouds surrounding Titan.
Park is clearly encouraged by the working relationship
between JPL's team of engineers and the visiting Italian engineers.
"Cooperation between the Italians and JPL has gone very
smoothly. They sent a very good team, and we worked together as
a good team," Park said.
According to Park, most communications between Alenia Spazio
and JPL are conducted via facsimile or telephone. He is hopeful
that as the project progresses, the Italian contractor will be
capable of communicating via electronic mail.
"There is only a one-hour window when we come in at 8 a.m.,
since it is 5 p.m. in Rome. So the physical window is really a
problem," Park explained.
He noted that even in this early phase of testing, the RFES
breadboard--an engineering term used to describe prototypes--is
unusually close to flight configuration. "They (Alenia Spazio)
wanted to verify some of the mechanical and electrical aspects of
their system early on," Park said. Their philosophy was to do
everything as close to flight as possible, starting with the
breadboard."
Kevin Wheeler, instrument engineer for the Cassini radar, is
pleased with the analysis of the interface between the two
subsystems, yet like most test engineers, he wishes his team had
more time for further testing.
"We only had two months, which is a short amount of time for
breadboard radar testing," Wheeler said. "But when you consider
the complexity of the radar, the interface itself, and the fact
that it performed well, I'd say it is a fairly good achievement."
In the short two months the Italian engineers spent at JPL,
they learned to cope with earthquakes, rush-hour traffic and
communicating in a foreign language, but through it all, each has
developed a new sense of their nation's capacity to explore of
the outer reaches of the solar system.
"Apart from our different languages, we are at the same
level from a technical point of view," Chiappi noted.
"The Italian people are aware of, and they are proud of this
mission because it is the first time the Italian Space Agency is
participating in a deep-space mission," he added.
"To come here and work is an honor," Borgarelli said. "We
have had the honor of working with the engineers at JPL, and we
have been given the opportunity to appreciate the capabilities
they have."
The Cassini spacecraft is a joint mission between NASA, the
European Space Agency and the Italian Space Agency. Scheduled for
launch in October 1997, Cassini will arrive at Saturn in 2004 and
begin a four-year orbiting tour to study the planet's
magnetosphere, satellites and rings.
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | [email protected]
| | | | __ \ /| | | | Jet Propulsion Lab |
___| | | | |__) |/ | | |__ Galileo S-Band | A mind stretched by a new
/___| | | | ___/ | |/__ /| Pasadena, CA 91109 | idea can never go back to
|_____|/ |_|/ |_____|/ | its original dimensions.
|
| 640.38 | Structural Testing | MTWAIN::KLAES | No Guts, No Galaxy | Thu Sep 08 1994 16:24 | 55 |
| From: US1RMC::"[email protected]" "Ron Baalke" 4-SEP-1994
To: [email protected]
CC:
Subj: Cassini Begins Structural Testing
From the "JPL Universe"
August 26, 1994
Cassini starts 15-month structural testing program
The Cassini project has begun a development test program, a
series of structural tests that will continue for the next 15 months.
"This is the first time we've stacked the core structure for
testing," noted Gary Coyle, Cassini mechanical system technical manager.
The lower portion on the stack comprises the flight launch
vehicle adapter, linear separation-assembly, and flight lower
equipment module.
The center section is actually mock-up hardware representing
the propulsion module structure and the Huygens probe, the latter
to be used in support of additional acoustic tests with the launch
vehicle fairing at Martin Marietta in Denver early next year, Coyle said.
The top of the stack is the flight upper equipment module,
comprising the conical upper shell structure and 12-bay bus. The
whole stack, he noted, is a little more than 6 meters (20 feet)
high. Radioisotope thermoelectric generator (RTG) and reaction
wheel mass simulators are attached to the lower equipment module
to complete the high-fidelity test configuration.
"The first of the development test program series is an
acoustic test, which is intended to characterize the response of
the RTGs and develop some form of response attenuation," Coyle explained.
In the JPL Acoustic Chamber test facility, huge speakers pound
out high-decibel sound to subject the stack to the kind of
environment the spacecraft will face at launch. The testing
identifies the way the spacecraft will respond and vibrationally
excite the RTGs. Once this response is understood, small vibration
dampers are attached to the structure to dampen the vibration
excitation to the RTGs at frequencies where they are particularly
vulnerable.
The team made the design modifications to add the dampers in
late July and about a week later took its "first peek at how well
they worked," Coyle said.
A significant improvement was evident in the data. "It looks
good from an attenuation standpoint," he noted. The modifications'
impact turned out to be a 22-kilogram mass penalty, which, Coyle
said, is a significant commitment of resources. Whether or not the
modification will be implemented is still being decided by the project.
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