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Original Date: Sat, 1 Apr 2000 19:20:14 +0200
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UniSci - Daily University Science News
Dramatic Change Coming In View Of The Universe
Astronomers looking at the very cold, far-infrared universe have
barely glimpsed what's there. They've had to make do with imaging
systems that survey the cosmos a few pixel points of light at a time.
And they've had to grab opportunities to observe from space or high in
the atmosphere, where the cosmic far infrared photons are visible.
Things will change dramatically with the launch of the Space Infrared
Telescope Facility (SIRTF) in December 2001.
SIRTF will fly three science instruments in orbit around the sun for
perhaps as long as five years -- as long as the liquid helium lasts to
keep the imaging systems cooled to near absolute zero.
One of the instruments, from the University of Arizona, will use the
first true imaging arrays at far-infrared wavelengths. It will detect
far-infrared objects 100 times fainter than have ever been seen
Where pioneering far-infrared surveys of the 1980s-1990s saw nearly
empty sky, SIRTF will get views packed with infrared-bright objects,
said University of Arizona astronomer George H. Rieke.
Rieke is principal investigator for the Multiband Imaging Photometer
for SIRTF (MIPS), the science instrument for the far infrared. The
MIPS is a highly sensitive camera that will take images of the coolest
objects in space, objects at temperatures between about minus 430 and
minus 300 degrees Fahrenheit.
Next Monday, April 3, Rieke and his entire UA Steward Observatory team
will be at Ball Aerospace in Boulder, Colo., to demonstrate that their
instrument meets NASA's requirements. They will hand over the
instrument officially a few weeks later.
Then MIPS will be mounted in a helium dewar (a kind of sophisticated
thermos bottle), cooled to 1.5 degrees Kelvin (or minus 457
Fahrenheit, just above absolute zero), mounted with the dewar in the
telescope and tested.
The completed telescope with instruments gets shipped next year to
Lockheed-Martin in Sunnyvale, Calif., where it will be installed in
the spacecraft and further tested. The full SIRTF observatory will
travel a few months before launch to the NASA Kennedy Space Center at
Cape Canaveral, Fla.
The Harvard-Smithsonian Center for Astrophysics (CfA) and Cornell
University are on a similar schedule for the other two SIRTF science
instruments. CfA has developed the Infrared Array Camera and Cornell
has developed the Infrared Spectograph.
Rieke's group began work on their camera in 1984, when SIRTF was
envisioned as a $2 billion mission. The SIRTF design was overhauled in
1994 to cut mission costs to under a half billion dollars. The UA team
contracted to build MIPS for $23.7 million. Advances in infrared
detectors allowed SIRTF to retain much of its power despite the huge
UA astronomer Erick T. Young, deputy principal investigator for MIPS,
led the Steward Observatory team that designed and built the first
far-infrared detector arrays for their part of the SIRTF mission. The
arrays will enable MIPS to see far-infrared objects never seen before.
"Such images will show us infrared-bright galaxies to the edge of the
known Universe, maybe even farther than any galaxies we have
discovered so far," Rieke said.
"And we can look around nearby sun-like stars for planetary debris
systems with emissions as wimpy as our own solar system emission.
"In fact, we've shown that MIPS, looking back from any close star,
could detect the finely-divided material we expect lies out in the
Kuiper Belt," he added. The Kuiper Belt is the system of small, faint
and very cold objects recently found beyond the orbits of Neptune and
But the real breakthroughs are up to the astronomical community, which
will get 80 percent of SIRTF observing time, Rieke emphasized. The
SIRTF Science Center at the California Institute of Technology will
issue a first call for observing proposals a month from now.
"With such an advance in capability, we expect that discoveries will
be made well beyond our currently imagined ones," Rieke said.
The UA camera on SIRTF contains three super-cooled detector systems
that operate at different wavelengths.
One array, supplied by Boeing North America, operates at 24 microns,
50 times the wavelength of visible light. (A micron is one-thousandth
of a millimeter.)
Another far-infrared array, built at Steward Observatory, is sensitive
to radiation at 70 microns. It contains 1,024 detectors, 100 times
larger than previous arrays operating in space at this wavelength.
Each detector has about 30 times the sensitivity of those in the
A third array, also built at Steward Observatory, operates at 160
microns, about 300 times the wavelength of visible light. There are 10
times as many detectors -- each 10 times more sensitive -- as in any
previous array operated in space at this wavelength.
All objects above the coldest possible temperature, absolute zero, or
minus 459 degrees Fahrenheit, emit infrared radiation, or heat. Helium
is used to chill the MIPS arrays to just 2 degrees Fahrenheit above
absolute zero to avoid blinding the arrays with heat from SIRTF
itself. - By Lori Stiles
THE MIPS SCIENCE TEAM
Eric Arens, University of California, Berkeley
Charles Beichman, California Institute of Technology
Steven Gaelema, Black Forest Engineering
T.Nicholas Gautier, Jet Propulsion Laboratory
Eugene Haller, Lawrence Berkeley National Laboratory
Charles Lada, Harvard Smithsonian Astrophysical Observatory
Frank Low, University of Arizona
Jeremy Mould, Mount Stromlo & Siding Spring Observatory
Gerry Neugebauer, California Institute of Technology
Paul Richards, University of California, Berkeley
Marcia Rieke, University of Arizona
Peter Strittmatter, University of Arizona
Michael Werner, Jet Propulsion Laboratory
THE STEWARD OBSERVATORY TEAM
Jeff Beeman - Detectors and Stimulators
Michael Bradley-Focal Plane Construction
Jim Cadien - Detector Testing
Cindy Davidson - Process Engineer
Jim Davis - Focal Plane Construction
Chad Engelbracht - Instrument Scientist
Kimberly Ennico - Instrument Science
Karl Gordon - Instrument Science
Dean Hines - Scientist-At-Large
Todd Horne - Research Specialist
Doug Kelly - Instrument Science
Dak Knight - Focal Plane Construction
Mary McCormick - Administrative Support
Tom McMahon - Systems Engineer
George Rieke - Principal Investigator
Gil Rivlis - Software, Computers, and Miscellaneous
Raz Quillen Rivlis - Destructive Test Consultant
Rick Schnurr - Stressed Ge:Ga Array Lead
John Stansberry - Instrument Science
Patsy Van Buren - Administrative Support
Debbie Wilson - Program Manager
Greg Winters - Focal Plane Engineer
Erick Young - Deputy Principal Investigator
SIRTF MISSION MEMBERS
Jet Propulsion Laboratory SIRTF Science Center, California Institute
Ball Aerospace and Technologies Corp.
Lockheed Martin Missiles and Space
Smithsonian Astrophysical Observatory
NASA-Goddard Space Flight Center
University of Arizona
[Contact: George H. Rieke, Erick T. Young, Lori Stiles]
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