Conference 7.286::space

  Wouldn't it make more sense to put SIRTF in low earth orbit rather
than 60,000 miles up so that the supply of liquid helium could be replaced
once in a while? Also, how do you do maintenance on something that high
up?

  George

The article mentions the desire to be above the Van Allen belts and the
atmosphere.  Perhaps also they need to be further from the infra-red re-radiating
Earth surface?  

    Re:.1
    
    	The primary reason to have SIRTF so high up is so that Earth won't
    get in its way. If it were in an orbit similar to HST and it was trying
    to take a long exposure of some object, the Earth would come into view
    for up to 45 minutes every hour and a half. HST gets around this by
    turning away from the Earth when it comes into view wait for it to pass
    and then go back to continue its observations (assuming its
    observations need more than one orbit). While it is possible for SIRTF
    to do the same thing, it is in general a real pain in the ass to do 16
    times a day. The best thing to do is to put SIRTF in a high orbit where
    the Earth would appear to be a disk only about 8 degrees wide that from
    the point of view of the spacecraft would circle the sky every four
    days. All in all the Earth would be much less of a bother.
    
    				Drew
    

Article: 32276
From: [email protected] (Steve Willner)
Newsgroups: sci.space,sci.astro
Subject: SIRTF Update
Date: 19 Feb 93 23:20:24 GMT
Sender: [email protected] (Steve Willner)
Organization: Smithsonian Astrophysical Observatory, Cambridge, MA,  USA
 
I've been meaning to post a progress report on SIRTF, the fourth (and
greatest, if it ever flies) of the Great Observatories.  As many of
you know, SIRTF was the highest priority recommendation of the decade
survey (Bahcall Committee) report, but the last year has seen a
reexamination and redesign of the project.  
 
The highlights are that the mission has been rescoped to reduce the
cost, but the key performance determinants (mirror size and lifetime)
have been retained.  This is still an observatory-class mission, not
an Explorer.  Meanwhile, the detectors that have been developed for
the program are making their way onto ground-based telescopes.  I'll
give an overview below and answer specific questions at the end.
 
The major effort in the rescoping was to get the mass down so as to
launch on an Atlas instead of a Titan.  The biggest change was to
plan a Solar orbit instead of high Earth orbit.  Essentially, SIRTF
will slowly drift away from the Earth and will reach a distance of
about 0.5 AU after five years.  This dramatically cuts the heat load
from the Earth at the price of reducing the data transmission rate.
The second change was to simplify the instruments to reduce the mass
that must be cooled.  This means that the straps holding the
instruments in place can be reduced in cross-section, which reduces
their heat conductance.  A third change was to recognize that the
newer detectors will generate less power than the old ones, so there
will be less heat input, further reducing strap size.  Finally, the
lifetime requirement was reduced from five years plus margin to three
years plus margin.  The net effect of these changes was to reduce the
amount of liquid helium required from 3800 liters to 920 liters.
(Obviously the reduction in helium mass and tankage further reduces
the cold mass and the strap size.)  For comparison, IRAS flew 520
liters and ISO will have 2140 liters.  The new design looks like a
telescope with a modest dewar wrapped around it.  The old design was
a much larger dewar with a telescope buried down in the middle.
 
Since the instruments now dominate the heat load (fully 75%), the
lifetime could go back up if the instrument heat generation can be
reduced.  (In the old orbit, Earth contributed most of the heat load.)
 
The mirror diameter remains at 85 cm.  (Sky and Telescope said it was
down to 70 cm, but they were wrong.)  Shrinking the mirror does not
save much money, since the observatory mass is determined by the
spacecraft, payload, helium, and structure and not by the telescope
itself.  The estimated mass is 1839 kg; launch capability of the
Atlas (I think it's a II AS, but I can't find the notes right now.)
is 2459 kg, so there's reasonable margin for this stage of the project.
 
The capabilities retained amount to imaging, mapping, and
spectroscopy at all wavelengths from 3 to 200 microns.  Major
scientific goals include studying the Universe at large redshift and
detailed study of star formation.  In fact, almost every field of
astronomy from the Solar System outward will be affected in some way. 
 
The instruments have been simplified considerably, but the core
capabilities have been retained.  The biggest losses are: 1) all
capability beyond 200 microns is gone.  This is a real loss, but it
is also a real simplification in such areas as baffling and
temperature stability requirements.  It also eliminates the adiabatic
demagnetization refrigerator, considered by some a technical risk.
2) The requirement for diffraction-limited spatial resolution at
wavelengths as short as 2.5 microns has been dropped.  This relaxes
requirements on the fine guidance system and on mirror quality.  The
wavelength at which diffraction-limited resolution will be provided
is subject to future technology developments but will be at worst
10 microns.  (I'd be willing to bet it will end up no worse than
5 microns and possibly as low as 3.5 microns.)  This is more of a
loss than it seems at first, though, since 3.5 microns is the ideal
wavelength for seeing the most distant objects.  3) Capability to
survey large areas quickly (as opposed to making long exposures on
small areas) has been compromised.  4) There are additional deletions
that mean some kinds of observations will take longer but will still
be possible.
 
The detectors for the 3 to 27 micron range have met (or nearly met)
all performance goals.  For example, the indium antimonide detectors
for 3 to 5.3 microns are being built in 256x256 format and are
delivering 90% quantum efficiency (with an anti-reflection coating),
10 electrons read noise, and less than 1 electron per second dark
current.  Some of these arrays are already in use on ground based
telescopes.  At wavelengths longer than 27 microns, individual
detectors have met the performance requirements, but there are still
issues of how to package them in the required array formats for
flight.  Nobody sees any show-stoppers, though.
 
The cost of the rescoped SIRTF will be considerably (35-40%) less
than the $1.3G estimated by the Bahcall committee.  (The Bahcall
committee did not include launch, as was customary when the report
was written.  In round numbers, we are talking something like $1G
_including_ the Atlas launch but _not_ corrected for inflation.)
 
The schedule is highly uncertain.  As far as I can tell, there's not
anybody in Washington who can say "yes" to any mission at the moment.
One reasonable schedule would be a two-year phase B starting in 1995
and a four year development/construction phase leading to launch in
2001.  Keep your fingers crossed.
 
In article <[email protected]>,
[email protected] (Dave Rickel) writes: 

> There was a proposal in SPACEFLIGHT a couple months back to build a
> large passively cooled IR telescope.  I seem to remember that they
> proposed sticking it in the L-2 spot (presumably the sun-earth L-2
> spot).  Is this SIRTF, or something else?
 
This is not SIRTF; I think it's Edison.  This is a scaled-down
version of Large Deployable Reflector (LDR).  Compared to SIRTF, it
gives up sensitivity by running warmer in order to achieve better
spatial resolution with a larger mirror.
 
At the moment, this is just a concept floating around, not a mission
that has been studied in any detail.  In spite of certain over-
enthusiastic claims (now retracted, I understand), Edison is no
replacement for SIRTF.
 
> Anyway, the article mentioned that there is enough thermal noise that it
> really wasn't worthwhile cooling the mirror all the way down to liquid
> helium temperatures; if you can passively cool the mirror (they mentioned
> temperatures like 40-60 K) you are no longer limited by the amount of He
> you carry along (larger mirrors, longer liftimes).
 
It depends on what wavelengths you want to work at.  For example, if
your wavelength cutoff is 5 microns, 100 K is adequate.  This can be
achieved by passive cooling (i.e. clever design and a bunch of
radiators on the cold side of the spacecraft) even in low Earth
orbit.  Getting colder is hard, though, even if you get away from the
Earth, because the power radiated goes as the fourth power of
temperature.  Thus to reach 50 K with a given design, the heat load
has to drop a factor of 16.  Getting much below 50 K with passive
cooling seems very difficult to me.
 
Warm telescopes also give less penalty at longer wavelengths (beyond
200 microns).  This is because even a cold telescope will still have
residual radiation, but the brightness goes more nearly linearly than
exponentially with temperature.  So it may pay to take the hit in
telescope brightness if you can fly a larger mirror, which gives both
more collecting area and better spatial resolution.
 
For the prime SIRTF range of 3 to 200 microns, though, if you want
sensitivity, there is no substitute for cooling the whole telescope.
The SIRTF focal plane will run at 2-3 K, the optics not much warmer.
(I can't find it right now, but I think the maximum baffle
temperature is 10 K.)
 
Somebody else wrote:

> Last I looked we cooled the detectors, not the mirror.  A mirror at 40 K
> might do strange things.
 
No, it has to be the whole thing if you want good sensitivity.  There
is some worry that cooling the mirror could change its figure, but in
practice, ISO has found it not to be a problem.  (The tolerances are
not as strict as optical telescopes, much less HST.)  The flight
telescope will have to be tested, of course.
 
> using four stage thermoelectric cooling to get down to temperatures around
> 180 K.  Might be somebody's looking at a 5 or 6 stage cooling scheme.
 
TE cooling doesn't seem to be practical for low temperatures.  (I
don't know why.  Thermodynamics says it should work great, but when I
investigated, it turned out that suitable coolers didn't exist.)
Flight qualified mechanical coolers are available to get to 30 K or
perhaps below, and the temperature limit could no doubt be decreased
if anybody wanted to spend the money.
 
> TE cooling would solve a lot of servicing problems.  But with the advances
> made over the last 10 or so years in closed cycle cryostatic refrigerators
> I'd think you could fly a He cooled detector array and keep it cooled for
> many years.
 
For the combination of reliability, mass, and cooling power, the
engineers say you still can't beat liquid helium.  Servicing is not
planned for any of the cryogenic telescopes.  The advantage of
getting away from the Earth is bigger than the advantage of being
able to service.
 
If there are more questions about SIRTF, I'll try to answer them.
-- 
Steve Willner            Phone 617-495-7123         Bitnet:   willner@cfa
Cambridge, MA 02138 USA                 Internet: [email protected]
  member, League for Programming Freedom; contact [email protected]

From:	US1RMC::"[email protected]" "Ron Baalke" 23-APR-1993 
To:	[email protected]
CC:	
Subj:	SIRTF Mission is Still Alive

From the "JPL Universe"
April 23, 1993

SIRTF is still very much in business

By Mark Whalen

     In these times of extra-tight NASA budgets, the very
survival of a number of missions has been uncertain. But thanks
to major design refinements implemented in recent months, JPL's
Space Infrared Telescope Facility (SIRTF) -- a major project
considered to be in trouble a couple of years ago -- is "alive
and well," according to Project Scientist Michael Werner.

     A lighter spacecraft, revised orbit and shorter mission have
added up to a less expensive project with "tremendous scientific
power" and a bright future, said Werner.

     Designed as a follow-up to the highly successful Infrared
Astronomical Satellite (IRAS) and Cosmic Background Explorer
(COBE) missions, SIRTF -- a cryogenically cooled observatory for
infrared astronomy from space -- is scheduled for launch in 2000
or 2001 if plans proceed as scheduled.

     IRAS' pioneering work in space-based infrared astronomy 10
years ago allowed astronomers to view the Milky Way as never
before and revealed, among other things, 60,000 galaxies and 25
comets. It provided a sky survey 1,000 times more sensitive than
any previously available from ground-based observations. COBE has
measured the infrared and microwave background radiation on large
angular scales, and revealed new facts about the early universe.

     But to illuminate SIRTF's potential, Jim Evans, JPL's
manager of Astrophysics and Fundamental Physics Pre-Projects,
recently said that the project is "1,000 to 1 million times more
capable than IRAS," based on technological advances in infrared
detector arrays.

     However, despite the enormous strides in infrared
exploration SIRTF promised, and the fact that it was cited as the
highest priority new initiative for all of astronomy in the 1990s
(by the National Academy of Sciences), it took a "diet or die"
directive from NASA Headquarters last year to keep the project
going, according to Werner.

     The project is now known as Atlas SIRTF, based on the key
factor in its new design: The satellite will orbit the sun
instead of the Earth, permitting the use of an Atlas rocket
launch instead of the formerly proposed and heavier Titan. "The
main advantage of the solar orbit is that you can use all of your
launch capability for boosting the payload -- you don't have to
carry up a second rocket to circularize the orbit," Werner said.
The other advantage to a solar orbit, he said, is that "it's in a
better thermal environment, away from the heat of the Earth."

     Additional major changes in SIRTF's redesign include
shortening the mission from five to three years and building a
spacecraft that is less than half as heavy as in the original
plan -- Atlas SIRTF will weigh 2,470 kilograms (5,400 pounds)
compared to Titan SIRTF's 5,500 kilograms (12,100 pounds).

     All of that adds up to "a less stressful launch
environment," Werner said, and a cost savings of more than $200
million for the launch, in addition to increased savings in the
design of the smaller, less massive spacecraft.

     Werner said SIRTF's redesign came as a result of Congress'
telling NASA "you're trying to do too many things. If you want us
to support SIRTF, which is a good project, develop a plan to see
how it fits into (NASA's) overall strategy."

     Shortly thereafter, SIRTF was named as NASA's highest
priority "flagship" scientific mission by the interdisciplinary
Space Sciences Advisory Committee, in addition to the blessing
from the National Academy of Sciences.

     While the spacecraft and its instruments required descoping
to keep the project alive, SIRTF's major scientific contribution
always promised to come about from its advanced infrared detector
arrays, which will allow images to be developed "tens of
thousands of times faster" than before, according to Evans.

     "Up until a couple of years ago," Werner said, "all infrared
astronomy was done with single detectors -- or very small arrays
of individually assembled detectors. Since then, the Department
of Defense has developed a program to produce arrays of tens or
hundreds of thousands of detectors, rather than just a few, and
those are very well suited for use on SIRTF."

     Werner noted that in addition to dealing with budget
pressures, Congress is currently watching NASA projects with an
eye out for any "technological spinoff."

     "On that question, I think we have some things to say," he
said, "because the detectors we're using are straight off various
military developments. Also, SIRTF will be built by the U.S.
aerospace industry, and it's a real technological and engineering
challenge in addition to being a tremendous scientific project.

     "SIRTF will be used by the entire astronomical community,"
Werner added, but the revised three-year mission "puts a premium
on observing time. We have to educate the user community and
develop a program that involves early surveys and quick
turnaround of the data."

     Werner said the downsizing of the project required a
reduction in scope and complexity of SIRTF's three instruments --
the infrared spectrograph, infrared array camera and multiband
imaging photometer. However, these reductions will only result in
losses of efficiency rather than capability, he said.

     The project hopes to start a "Phase B" activity in 1995,
which will provide a detailed concept for development and design.
Building the hardware would begin about two years later.

     Projected cost estimates, Evans said, are $850 million-$950
million.

     "I am very optimistic about SIRTF," he said. "It will
provide a tremendous return for the investment."

     Werner added that an additional benefit from the project
will be the "enrichment of our intellectual and cultural
environment. People on the street are very interested in
astronomy ... black holes, the possibility of life on other
planets, the origin of the universe ... and those are the kind of
questions SIRTF will help answer."

     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [email protected]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | The aweto from New Zealand
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | is part caterpillar and
|_____|/  |_|/       |_____|/                     | part vegetable.

% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% From: [email protected] (Ron Baalke)
% Subject: SIRTF Mission is Still Alive
% Organization: Jet Propulsion Laboratory
% Date: Fri, 23 Apr 1993 17:29:00 GMT

From:	US1RMC::"[email protected]" "Ron Baalke" 14-JUL-1993 
To:	[email protected]
CC:	
Subj:	SIRTF Fact Sheet

            SPACE INFRARED TELESCOPE FACILITY (SIRTF)
                           FACT SHEET
                            JULY 1993

     A NASA mission that could probe hundreds of thousands of
celestial objects invisible to conventional telescopes is under
study at the Jet Propulsion Laboratory.

     The Space Infrared Telescope Facility (SIRTF) would launch
an orbiting observatory to study the universe in the infrared. 
SIRTF -- pronounced sir-tiff -- would be launched early in the
next decade.

     During its three year operation the telescope would collect
images of the birth of stars and galaxies; study objects ranging
from nearby comets and asteroids to the distant beacons of
quasars; and search for solar systems around other stars in ways
impossible for optical telescopes.

     SIRTF would complete NASA's series of "Great Observatories,"
telescopes in Earth orbit that study the universe at wavelengths
ranging from visible light to X-rays and gamma rays.

     The new spacecraft would render its images not from the
palette of colors in visible light but rather from the infrared
energy -- or, simply, radiated heat -- from celestial objects.

     Conventional optical telescopes can only study stars and
other objects that are glowing brightly enough to emit light in
the visible spectrum.

     Yet many of the most intriguing phenomena in the universe --
planets forming around other stars, vast stretches of dark dust,
stars in the process of birth -- are invisible in the regular
spectrum.  They are bright, however, in the infrared.

     Other celestial objects that give off visible light are
hurtling away from us so rapidly that the effect of "red shift"
moves the light energy we see into the infrared.

     Because any heat from SIRTF itself would interfere with
observations of distant celestial objects, special cooling
equipment must be installed onboard the telescope.

     The telescope itself would be surrounded by a massive
cooling system filled with liquid helium.  The equivalent of a 
giant Thermos bottle, the system keeps the infrared detectors and
the telescope cooled to less than 2 degrees Celsius (4 degrees
Fahrenheit) above absolute zero, -273 C (-459 F).

     As currently envisioned, SIRTF could be launched in 2001 or
2002 on an Atlas IIas rocket into a solar orbit in which the
spacecraft drifts slowly away from Earth.

     This orbit is designed to put SIRTF beyond not only Earth's
obscuring atmosphere but also the heat which is radiated off the
planet.  A solar orbit also allows uninterrupted viewing of a
large portion of the sky.

     The spacecraft has a complement of three sensitive
instruments:  the Infrared Array Camera and the Multiband Imaging
Photometer, which together will provide imaging at all infrared
wavelengths; and the Infrared Spectrograph, which will study the
chemical spectra of objects.

     SIRTF is a follow-on to the Infrared Astronomical Satellite
(IRAS), a joint mission of the United States, the Netherlands and
the United Kingdom.  Launched in 1983, IRAS gave astronomers a
profoundly new view of the universe -- revealing hundreds of
thousands of new stars and galaxies, discovering new comets and
offering the first glimpses of solar systems forming around other
stars.

     The IRAS mission, however, was designed only to conduct a
relatively brief sky survey.  The mission ended when the helium
coolant onboard IRAS was depleted after 10 months in orbit.

     SIRTF will be at least 1,000 times more sensitive than IRAS
and will operate more than three times longer.  Whereas IRAS used
a system of 60 infrared detectors, SIRTF will take advantage of
new types of arrays with up to hundreds of thousands of
detectors.  Combined, those capabilities will allow SIRTF to
carry out a rich diversity of highly detailed observations
pushing considerably beyond the general sky survey provided by
the previous satellite.

     A launch in 2001 would put SIRTF in orbit two centuries
after infrared energy was discovered by the German-English
astronomer Sir William Herschel in 1800.

     Herschel -- also known as the discoverer of the planet
Uranus -- was examining how sunlight is broken down into various
colors by a prism.  While carrying out experiments he decided to
compare the temperatures of the various colors of light.

     After placing thermometers in patches of colored light cast
by a prism, Herschel happened to place a thermometer in the
seemingly dark area beyond the red patch of light.  He was 
surprised to find that there, too, the thermometer registered a
temperature increase.

     In his paper reporting the experiment, Herschel told of his
discovery of "invisible rays of the Sun" transporting radiant
heat -- what would become known as infrared energy.

     The first infrared observation of a star other than the Sun
was made not by a professional astronomer but by the American
inventor Thomas Alva Edison in 1878.

     A year after his invention of the phonograph, the 31-year-
old Edison -- then the holder of 89 patents -- learned of a total
solar eclipse that would be visible from the western United States.  

     For the occasion, Edison fabricated an infrared sensor he
called a "tasimeter" capable of detecting temperature changes of
as little as a millionth of a degree.

     Traveling by train to the Wyoming Territory, Edison met up
with astronomers and set up his equipment in a frontier hen house
to observe the eclipse.  While adjusting his device he trained it
on Arcturus, a bright star in the constellation Bootes -- thus
inaugurating the discipline of infrared astronomy.

     Edison's astronomical interests soon fell by the wayside as
he put his energies into the incandescent light bulb and his
other inventions to come.  Most of the attention in astronomy
shifted to the very large optical telescopes being built on
mountaintops around the turn of the century.

     By the mid-20th century, improvements in technology allowed
astronomers to extend their vision beyond visible light to study
unseen radiation -- radio waves, X-rays -- coming from sources in
the universe.

     Infrared energy proved more difficult to study, however,
because most of the faint amounts coming from distant stars and
galaxies is blocked by Earth's atmosphere.

     In the 1960s astronomers worked to overcome this obstacle by
placing infrared instruments in NASA jets flying at altitudes of up 
to 50,000 feet, and on balloons ascending as high as 100,000 feet.

     Although revealing, these studies were inevitably limited
because of the short duration of the jet flights and the
difficulty of controlling the balloons precisely.

     The most dramatic look at the infrared universe thus still
awaited astronomers until the launch of IRAS in January 1983.  
During its 10 months in orbit, IRAS amassed a sky catalog of some
250,000 objects.

     Directed at the bright star Vega in the constellation Lyra,
IRAS found too much heat to be accounted for by the star alone. 
Astronomers concluded Vega is surrounded by an orbiting swarm of
pebble-sized dust grains that could be remnants from the
formation of a planetary system.

     Sifting through IRAS data, astronomers have since identified
more than a dozen other stars that appear to be orbited by such
solar system debris.

     The 1983 satellite also captured intriguing views of stars
in the process of birth and decline, as well as the first
assessment of dark dust woven through the Milky Way Galaxy
between the visible stars.

     Within the solar system, IRAS discovered a half dozen new
comets, including one that passed within 3 million miles of Earth
as it swept inward toward the Sun.

     Because of its limited lifetime -- dictated by the amount of
liquid helium onboard -- and the capabilities of its sensors,
IRAS was destined to provide a general sky survey that raised as
many questions as it answered.

     Such questions are the focus for the SIRTF mission.  

     One area SIRTF will be able to probe is the realm of very
young galaxies in the process of forming.  Many of the stars in
such galaxies are cool red giants that are most visible in the
infrared spectrum.  Visible light from such galaxies is often
obscured by dust surrounding the galaxies.

     Violent collisions between galaxies that could be
responsible for the origin of quasars is another topic for SIRTF
study.  Quasars and other active galactic nuclei are thought to
be powered by massive black holes at their centers, but much of
this activity is obscured by gas and dust.  SIRTF will provide a
better picture in the infrared.

     Gas and dust similarly throw a cloak around the birth of
stars, both nearby within the galaxy and beyond.  SIRTF will be
able to study star formation in areas including nearby stellar
nurseries where stars like the Sun are being created.

     The creation of heavy elements when stars collapse and
abruptly burst as supernovas is another area for SIRTF study. 
The orbiting telescope will be sensitive enough to examine
supernovas tens of millions of light-years away.

     SIRTF will also be able to search for brown dwarfs.  These
are bodies -- some orbiting stars, others on their own -- which
are much more massive than even giant Jupiter-sized planets but
are too small to ignite as stars themselves.  Though predicted by
theory, their existence as yet remains to be confirmed.

     IRAS's revelation of what may be signs of solar systems
swirling around other stars will be greatly improved upon by
SIRTF.  The new spacecraft will be able to examine the systems
that IRAS discovered in much greater detail, and search for other
systems.

     Closer to home, SIRTF's capabilities will be useful in
studying planets, comets, asteroids and dust within the solar
system.  Chemical spectra from SIRTF's instruments will give
definitive information, for example, on the atmospheres and icy
surfaces of Pluto and its moon Charon -- the only known planet as
yet unvisited by a NASA spacecraft.

     And at the other extreme of the cosmos, SIRTF will provide
data on infrared sources that will help astronomers understand
data from NASA's Cosmic Background Explorer (COBE) satellite. 
Launched in 1989, COBE studied background infrared and microwave
radiation, including the radiation believed to be left over from
the Big Bang that gave rise to the known universe.  Along with
IRAS, COBE was the chief predecessor to SIRTF in the technologies
needed to launch a space infrared telescope.

     Many scientific inquiries will benefit from combining
observations from SIRTF with those from NASA's other "Great
Observatories" -- the Hubble Space Telescope, the Gamma Ray
Observatory and the Advanced X-ray Astrophysics Facility.

     When the nearby supernova SN 1987A burst into view four
years ago, for example, astronomers took advantage of special
NASA expeditions using balloons and airborne observatories to
study the exploding star at all wavelengths.  SIRTF and the other
orbiting observatories will be able to gather similar data on
much more distant supernovas.

     Project management for SIRTF has been assigned to NASA's Jet
Propulsion Laboratory, Pasadena, Calif.  Other participating
centers of the space agency include NASA Headquarters,
Washington, D.C.; NASA's Ames Research Center, Moffett Field,
Calif.; and NASA's Goddard Space Flight Center, Greenbelt, Md.

     Participating in the development of SIRTF and its
instruments are scientists representing the California Institute
of Technology; Cornell University; Pennsylvania State University;
Smithsonian Astrophysical Observatory; Steward Observatory of the
University of Arizona; University of California, Berkeley;
University of California, Los Angeles; and University of Rochester.

     In addition to SIRTF's investigators, astronomers in the
general scientific community will be invited to use a major
portion of the observing time on the orbiting telescope.

     At JPL, James Evans is SIRTF project manager.  Dr. Michael
Werner is project scientist.  JPL manages the SIRTF project for
NASA's Office of Space Science.

     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [email protected]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | There is no such thing as
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | a "temporary" tax increase.
|_____|/  |_|/       |_____|/                     |