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) on Friday, April 18.

SIRTF will fly three science instruments in orbit around the sun for a
minimum two-and-one-half year mission. It is the last of NASA’s Great
Observatories, which also include the Hubble Space Telescope, the Chandra
X-ray Observatory and the Compton Gamma Ray Observatory.

One of the SIRTF 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 before.
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 (MIPS).
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.

Rieke and his UA Steward Observatory team delivered their instrument to Ball
Aerospace in Boulder, Colo., for testing, and then to NASA in March 2000.
MIPS was 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) with the telescope, and again tested. From there it went to
Lockheed-Martin in Sunnyvale, Calif., where it was installed in the
spacecraft and further tested.

The full SIRTF observatory is being readied for launch at the NASA Kennedy
Space Center at Cape Canaveral, Fla. The SIRTF mission is managed for NASA
by the Jet Propulsion Laboratory, Pasadena, Calif.

The Harvard-Smithsonian Center for Astrophysics (CfA) and Cornell University
have developed the other two SIRTF science instruments. CfA has developed
the Infrared Array Camera and Cornell University 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 budget cut.

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, providing an entirely new perspective on how galaxies and massive
black holes formed," 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 Pluto.

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 administers observing
proposals.

"With such an advance in capability, we expect that discoveries will be made
well beyond our currently imagined ones," Rieke said.

Tucson-based members of the MIPS science team since 1984 also include
Regents’ Professor emeritus Frank J. Low, astronomy Professor Marcia Rieke,
UA Steward Observatory Director and Regents’ Professor Peter A.
Strittmatter, and Jeremy Mould, director of the National Optical Astronomy
Observatory.

Mould has a particular interest in what MIPS’ improved sensitivity will
reveal about the early formation of galaxies, and the role of galaxy mergers
in this process, from about 500 million years after the Big Bang to six
billion years later.

"Galaxies tend to have strong infrared signatures when they formed from
mergers because of the burst of star formation and dust production that
naturally follows such a merger," Mould explained.

Mould’s recent paper on this subject, "A Model for SIRTF Galaxy Counts" will
be published in the Astrophysical Journal Letters on April 20. The MIPS
Surveys Team will test predictions in the paper. For more, see
http://lully.as.arizona.edu/GTODeep/Public/

THE MULTIBAND IMAGING PHOTOMETER – 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 earlier arrays.

A third array, also built at Steward Observatory, operates at 160 microns,
which is 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.

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, National Optical Astronomy 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

Steward Observatory team

  • * Almundena Alonso-Herrero – Science Team
  • * Jeff Beeman – Detectors and Stimulators
  • * Myra Blaylock – Documentation
  • * Michael Bradley-Focal Plane Construction
  • * Jim Cadien – Detector Testing
  • * Jim Davis – Focal Plane Construction
  • * Herve Dole – Science Team
  • * Elichi Egami – Science Team
  • * Chad Engelbracht – Instrument Scientist
  • * Karl Gordon – Data Analysis Scientist
  • * Dean Hines – Scientist-At-Large
  • * Doug Kelly – Instrument Science
  • * Karl Misselt – Science Team
  • * Jane Morrison – Software Development, Data Analysis
  • * James Muzerolle – 24-micron Array Scientist
  • * Becky Ohlau – Administrative Support
  • * Casey Papovich – Science Team
  • * George Rieke – Principal Investigator
  • * Rick Schnurr – Stressed Ge:Ga Array Lead
  • * John Stansberry – Deputy Test Scientist
  • * Kate Su – Science Team
  • * Patsy Van Buren – Administrative Support
  • * Debbie Wilson – Program Manager
  • * Erick Young – Deputy Principal Investigator

SIRTF mission members

  • * Jet Propulsion Laboratory
  • * SIRTF Science Center, California Institute of Technology
  • * Ball Aerospace and Technologies Corp.
  • * Lockheed Martin Missiles and Space
  • * Smithsonian Astrophysical Observatory
  • * NASA-Goddard Space Flight Center
  • * Cornell University
  • * University of Arizona

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