Infrared space-based astronomy on front burner for Caltech employees at the SIRTF Science Center

The telescope is NASA's newest triumph in the ongoing quest to understand the universe by looking at it in the pristine view of outer space, above the atmosphere and moisture. Following the Hubble Space Telescope, the Compton Gamma-Ray Observatory, and the Chandra X-Ray Observatory, SIRTF is the fourth and final mission of NASA's Great Observatories Program--though by no means the last time NASA intends to launch an observatory into space.

Caltech's part in the program is the hosting of the center where observations will be chosen, the satellite's observations scheduled and programmed, and the scientific data processed and sent on to the scientists involved. In all, about 100 people are employed by the center, which has close ties with the Jet Propulsion Laboratory and the Infrared Processing Analysis Center (IPAC) next door.

The science center is located in an office building on the south side of the Caltech campus in Pasadena, and the third-floor control room affords the staff a rather nice view of a sunny Southern California boulevard with palm trees and the San Gabriel mountains.

Now trailing Earth in a solar orbit slightly larger than Earth's annual orbit around the sun-- and thus slightly slower--the telescope will soon begin returning images of the infrared sky as it has never been seen before. There are much larger infrared telescopes on the ground, but unlike SIRTF, they are hampered by water vapor and atmospheric distortions. On the other hand, there have been infrared instruments in space, but none as big as SIRTF.

With such an instrument, astrophysicists hope to gain new insights about star formation, the center of galaxies, objects now so far away that they can only be imaged in the infrared, brown dwarfs so cool that they do not emit visible light, and perhaps even the extremely dim large bodies that may exist hitherto undetected at the fringes of our own solar system. Also, the telescope will be able to see light coming through many of the gas and dust clouds that are impenetrable to regular visible light.

Tom Soifer, the Caltech physics professor who has directed the center since its inception in 1997, admits he was nervous watching SIRTF being launched from Cape Canaveral in late August, but says he is pleased with the way things have gone so far.

In fact, the infrared telescope has already returned its first picture, an image of a star field. In SIRTF's case, the image was part of the "aliveness test" to demonstrate that the three scientific instruments on board all successfully survived the launch and subsequent deployment in solar orbit.

Soifer points out that the image (available at the Web site listed at the bottom of the page) was taken just a week after the telescope was launched. And even though the first image is a star field with no particular scientific interest, the bright, red stars give an inkling of the visual displays that will be made available to the public during SIRTF's five-year mission. In fact, subsequent images will be even better, because SIRTF's telescope wasn't even fully cooled or in focus when the "aliveness" image was snapped.

The imagery of SIRTF should be of ongoing interest to the public, because the remarkable images returned over the last 13 years by the Hubble Space Telescope have been quite popular. Also, the SIRTF operations will have more than a passing resemblance to those of Hubble, Soifer explains.

"SIRTF is very similar to the Hubble operation," he says. "Any astronomer in the world can get observing time if their proposal is selected, and you get grant money to fund your research if you work in the United States.

"Education and public outreach are important aspects of the science center, and we're working closely with JPL on public affairs activities."

Like the Hubble Space Telescope, SIRTF will look at a huge variety of objects, both in our own solar system and far beyond. In addition to the aforementioned items of interest, SIRTF will also look at giant molecular clouds, some of which contain organic molecules, and will look for signatures of planet formation around other stars.

Unlike the Hubble, however, SIRTF will have a more defined mission--or at least a more defined lifespan. The instruments must be cooled to an extremely low temperature with on-board cryogenic liquid, and this means that the bulk of the observations will end when the liquid coolant runs out. Minimizing heat and thereby conserving coolant is the reason for the unique orbit, which keeps the telescope well away from Earth, and conservation of the refrigerant is also the reason for the meticulous computer-aided planning that goes into all operations. The less the telescope has to move and switch between its three main instruments, the longer the coolant will last.

Soifer expects the mission to last for about five years. There's a chance that a few very limited observations could still be done for an additional four years, but SIRTF definitely comprises a beginning, a middle, and an end.

After that, SIRTF will be some 80 to 90 million miles away from Earth, and the distance will continue to increase. After about 60 years, Earth will catch up with SIRTF, but there would hardly be an advantage in rejuvenating the telescope at that point.

"It wouldn't be worth it," Soifer says. "The technologies are all advancing, so it would be better to go with that generation's technology. So there's a very clear end.

"In fact, the end will be approximately when I get to retirement age," he adds, smiling. "I'm not really sure how I feel about that."