NASA's Space Infrared Telescope Facility (SIRTF), built, integrated and tested at Lockheed Martin facilities in Sunnyvale (CA), roared into space Monday morning at 1:35 am EDT from the NASA Kennedy Space Center in Florida. NASA says that this newest satellite, with its infrared eyes, "...will open a new window on the universe, using infrared technology to study celestial objects that are either too cool, too dustenshrouded or too far away to be seen otherwise."

SIRTF's Cryogenic Telescope Assembly, which includes the scientific instruments, was built by Ball Aerospace in Boulder (CO), and was delivered to Lockheed Martin Space Systems in Sunnyvale in February 2002 and integrated with the Lockheed Martin-built spacecraft. (Lockheed Martin Space Systems is also providing mission support for SIRTF spaceflight operations in conjunction with the Jet Propulsion Laboratory (JPL) and the California Institute of Technology.)

"The Space Infrared Telescope Facility will complete NASA's suite of Great Observatories, a program that includes three previous missions that studied the universe with visible light, X-rays and gamma rays," said Dr. Ed Weiler, associate administrator for space science, NASA Headquarters, Washington. "Many cosmic objects produce radiation over a wide range of wavelengths, so it's important to get the whole picture." The three previous Great Observatories are the Hubble Space Telescope, Compton Gamma Ray Observatory and Chandra X-ray Observatory.

"We are extremely proud of our decades of work on behalf of NASA, and such a key role in NASA's newest space observatory," said John Straetker, Lockheed Martin SIRTF program manager. "It is particularly satisfying for our team to see SIRTF off on its way into deep space to begin its historic mission."

SIRTF is a cryogenically cooled space observatory that will conduct infrared (IR) astronomy during a two and one-half-to-five year mission. SIRTF completes NASA's family of Great Observatories, which 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 JPL 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.

The spacecraft itself features several technological breakthroughs, and the out-of-theordinary mission design will pay dividends as well. "The innovations have substantially reduced mission development costs," said Project Manager Dave Gallagher at JPL. "For example, the mission's Earth-trailing orbit simplifies scheduling and operations. And because the telescope detects heat from relatively cool objects, we have to keep it extremely cold. We've found a more efficient way to cool the telescope and slash the amount of liquid helium the observatory must carry."

An 'Earth-Trailing' Orbit?

An important feature of the SIRTF mission is the adoption of a solar orbit. To reach this orbit, the spacecraft was 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 would many possible alternate orbits that would have kept 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.

FMI: www.lockheedmartin.com; www.jpl.nasa.gov/webcast/sirtf; http://sirtf.caltech.edu; http://origins.jpl.nasa.gov