NASA's Space Infrared Telescope Facility (SIRTF) has completed integration, testing and prelaunch checkout at Lockheed Martin Space Systems in Sunnyvale, California, and has been delivered to the NASA Kennedy Space Center in Florida for an April 2003 launch. SIRTF's Cryogenic Telescope Assembly, which includes the scientific instruments, was built by Ball Aerospace in Boulder, Colo., and was delivered to Space Systems in Sunnyvale in February 2002 and integrated with the Lockheed Martin-built spacecraft.

"We are very pleased to have completed integration and testing of NASA's latest space observatory," said John Straetker, Lockheed Martin SIRTF program manager. "Environmental and other comprehensive tests done here in Sunnyvale have confirmed that SIRTF is a healthy Observatory, ready for integration with the launch vehicle. We look forward with anticipation to the upcoming launch."

SIRTF is a cryogenically-cooled space observatory that will conduct infrared (IR) astronomy during a two and one-half-to-five year mission beginning in 2003. SIRTF completes NASA's family of Great Observatories that also includes the Hubble Space Telescope, the Chandra X-Ray Observatory and the Compton Gamma Ray Observatory. The SIRTF program, a cornerstone of NASA's Origins Program, is managed by the Jet Propulsion Laboratory in Pasadena, Calif. for NASA's Office of Space Science in Washington DC.

The spaceborne SIRTF observatory comprises a 0.85-meter diameter telescope and three scientific instruments capable of performing imaging and spectroscopy in the 3-180 micron wavelength regime. Incorporating the latest in large-format infrared detector array technology, SIRTF will provide more than a 100-fold increased in scientific capability over previous IR missions. Cornell University, University of Arizona, and the Harvard-Smithsonian Center for Astrophysics have provided the instruments for SIRTF.

An important feature of the SIRTF mission is the adoption of a solar orbit. To reach this orbit, the spacecraft will be launched on a Delta 7920 launch vehicle with slightly greater than terrestrial escape velocity. The resulting orbit will have SIRTF trailing the Earth in its orbit around the Sun. This orbit makes better use of launch capability than do many possible alternate orbits that would keep SIRTF in orbit around the Earth. It permits excellent, uninterrupted viewing of a large portion of the sky without the need for Earth-avoidance maneuvers. In addition, the absence of heat input from the Earth provides a stable thermal environment and allows the exterior of the telescope to reach a low temperature via radiative cooling.

A one meter-diameter transmitting antenna fixed to the bottom of the spacecraft will be used twice each day to transmit 12 hours of stored science data to stations of NASA's Deep Space Network. In this manner, an adequate average data rate of 85 kbps-- corresponding to one image from SIRTF's largest array every 10 seconds -- can be maintained over the lifetime of the mission.

SIRTF's scientific potential is rooted in four basic physical principles that define the importance of infrared investigations for studying astrophysical problems:

  -- Infrared observations reveal cool states of matter: Solid bodies in
     space -- ranging in size from sub-micron-sized interstellar dust grains
     to giant planets -- have temperatures spanning the range from 3K to
     1500K (above which nearly all solids evaporate). Most of the energy
     radiated by objects in this temperature range lies in the infrared part
     of the spectrum. Infrared observations are therefore of particular
     importance in studying low-temperature environments such as dusty
     interstellar clouds where stars are forming and the icy surfaces of
     planetary satellites and asteroids.
  -- Infrared observations explore the hidden Universe: Cosmic dust
     particles effectively obscure parts of the visible Universe and block
     our view of many critical astronomical environments. This dust becomes
     transparent in the infrared, where observers can probe optically
     invisible regions such as the center of our Galaxy (and other galaxies)
     and dense clouds where stars and planets may be forming. For many
     objects -- including dust-embedded stars, active galactic nuclei, and
     even entire galaxies -- the visible radiation absorbed by the dust and
     re-radiated in the infrared accounts for virtually the entire
     luminosity.
  -- Infrared observations access unique spectral features: Emission and
     absorption bands of virtually all molecules and solids lie in the
     infrared, where they can be used to probe conditions in cool celestial
     environments. Many atoms and ions have spectral features in the
     infrared that can be used for diagnostic studies of stellar atmospheres
     and interstellar gas, exploring regions that are too cool or too dust-
     enshrouded to be reached with optical observations.
  -- Infrared observations reach back to the early life of the cosmos: The
     cosmic redshift which results from the general expansion of the
     Universe inexorably shifts energy to longer wavelengths in an amount
     proportional to an object's distance. Because of the finite speed of
     light, objects at high redshift are observed as they were when the
     Universe and those objects were much younger. As a result of the
     expansion of the Universe, most of the optical and ultraviolet
     radiation emitted from stars, galaxies, and quasars since the beginning
     of time now lies in the infrared. How and when the first objects in the
     Universe formed will be learned in large part from infrared
     observations.

Apart from a few windows at short wavelengths, all of the infrared radiation emitted by the above objects is absorbed by Earth's atmosphere. Worse, the infrared emission of the atmosphere itself blinds astronomers peering through those windows. Hence the need for a cooled space-based infrared observatory with high sensitivity -- SIRTF.

NASA's Origins Program follows the chain of events that began with the birth of the Universe at the Big Bang. It seeks to understand the entire process of cosmic evolution from the formation of chemical elements, galaxies, stars and planets, through the mixing of chemicals and energy that cradles life on Earth, to the earliest self-replicating organisms and the profusion of life. In short, Origins hopes to answer the fundamental questions: Where did we come from? Are we alone?

Lockheed Martin Space Systems Company is one of the major operating units of Lockheed Martin Corporation. Space Systems designs, develops, tests, manufactures, and operates a variety of advanced technology systems for military, civil and commercial customers. Chief products include a full-range of space launch systems, including heavy-lift capability, ground systems, remote sensing and communications satellites for commercial and government customers, advanced space observatories and interplanetary spacecraft, fleet ballistic missiles and missile defense systems.

For more information about Lockheed Martin Space Systems, see our website at http://lmms.external.lmco.com/ .

CONTACT: Buddy Nelson, +1-510-797-0349, or pager, +1-888-916-1797, or buddynelson@mac.com, for Lockheed Martin Space Systems Company.

SOURCE: Lockheed Martin Space Systems Company