ITHACA, N.Y. -- All ready to begin its search for the earliest, coldest and dirtiest parts of the cosmos, the Space Infrared Telescope Facility (SIRTF) arrived March 6 at the Kennedy Space Center, Cape Canaveral, Fla. It is scheduled for launch Tuesday, April 15, at 4:34:07 a.m. aboard a Boeing Delta II rocket.
One of the three instruments carried by the observatory is an infrared spectrograph (IRS) designed by Cornell University researchers and built by Ball Aerospace.
Final tests on the IRS to verify its safe passage to Florida from Lockheed Martin in Sunnyvale, Calif., will be carried out by the principal investigator on the spectrograph, James R. Houck, the J.A. Wallace Professor of Astronomy at Cornell.
The orbiting telescope, managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the last mission of NASA's Great Observatories program, which includes the Hubble Space Telescope, the Chandra X-ray Observatory and the Compton Gamma Ray Observatory. The IRS will peer into deep regions of the universe not visible optically. The IRS, it is hoped, will provide clues to the youngest parts of the heavens and show astronomers when star and galaxy formation began. Houck says the IRS can penetrate obscuring dust in the dirtiest parts of the cosmos and observe ultrafrigid, newly forming stars in the coldest regions of the universe. "For every question we answer, we dredge up three more," says Houck. "We're still in the process of finding out just how ignorant we are."
The observatory will trail the Earth in its orbit around the sun, with the instruments functioning in an environment where temperatures are slightly above absolute zero (-273 degrees Centigrade or -460 degrees Fahrenheit). With no moving parts, the IRS consists of two physically separated sections. The IRS cold assemblies are located within the SIRTF multiple-instrument chamber, and the warm electronics are in the SIRTF spacecraft bus. The spectrometer spreads light in wavelengths to create spectra, within which astronomers can study the atomic and molecular fingerprints found deep in the universe.
The idea of peering deep into the cold regions of the cosmos with an infrared spectrograph goes back more than three decades. Astronomers had found intense infrared radiation in the universe in 1968. Three years later a team of Cornell astronomers, led by Martin Harwit, now a Cornell emeritus professor of astronomy, and by Houck, then an assistant professor, sent rocket-borne instruments, cooled with liquid helium, about 118 miles above Earth. They learned that the distant, cosmic radiation was 20 times more intense than previously thought.
In 1978 Houck conducted infrared experiments from airplanes. It was then that he and his colleagues persuaded NASA there was an opportunity for placing a great telescope into space to study the infrared band of the spectrum, and perhaps uncover previously unseen parts of the universe. NASA agreed and sent out a request for proposals in 1983. In April 1984, Houck received the space agency award. That award, after several design and mission changes, has become the IRS.
According to NASA, SIRTF is scheduled to arrive at Pad 17-B on April 2 and will spend approximately two weeks atop the Delta rocket. The payload fairing will be placed around the telescope April 5. Then the observatory's dewar, used to cool the detectors and optical elements, will be cryogenically topped off with super-cold liquid helium to its maximum capacity of 360 liters (90 gallons), chilled to near absolute zero. This will increase the detectors' sensitivity to infrared light. Filling the spacecraft dewar will take approximately six days. Finally, two days before launch, according to NASA, the Delta launch vehicle's second stage will be fueled.
Houck says he cannot wait to see what surprises lurk in the deep reaches of the cosmos. "The real payoff will be the discoveries we didn't anticipate. They'll be startling, and as astronomers, we'll ask ourselves, 'why didn't we think of that?'" he says.
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o SIRTF: http://sirtf.caltech.edu/index.html