SOFIA's First Light

Jupiter seen in infrared light through SOFIAAfter nearly a 14-year hiatus, NASA is once again conducting astronomical observations…from the stratosphere!

SOFIA—the Stratospheric Observatory For Infrared Astronomy, a joint project between NASA and Germany—made its scientific debut in a "first light" flight on May 26th. That is, after a few years of test flights focused on the mechanical and aerodynamic engineering aspects of this 747-with-telescope, a science team acquired the observatory's first astronomical data.

Some of you may be thinking, NASA has an observatory built into an airplane? Really?

I had the same thought, until a job opening came up on NASA's previous flying telescope, the Kuiper Airborne Observatory. It was 1989, I was freshly back from my Peace Corps tour in Africa, and I was looking for a job. My physics advisor told me of the job opening, and I quickly put together a resume and sent it in.

I was invited to an interview, then waited a couple weeks with no word from my would-be employer. Sooooo…I called their HR office to ask if the position had been filled. "We have decided to offer you the position," the woman responded, "and, can you start on Tuesday? And…do you think you would be able to go to New Zealand on Friday for training?"

So my work on the KAO began with one of the job's best perks: I had to go wherever the observatory flew, and as it happened when I was hired, it was in New Zealand observing the southern skies….

But that was then, and the plane was a C-141A "Starlifter" (apt name!) and the telescope had a 1-meter mirror. This is now: SOFIA sports a 2.5 meter telescope in a 747SP.

What was the first target for SOFIA science? Amusingly, it was the same object that the KAO observed on its last flights, back in 1995: Jupiter. On the KAO flight, Jupiter was observed mostly as a "calibration" object to prep the scientific instrument for its principal target—and to serve as an "ooo!" and "ahh!" subject for the school kids who were "flying" along with us via satellite-linked telepresence (they were actually in their classrooms, in Hawaii and Texas).

But SOFIA used its first-light debut to explore the outflow of heat from within Jupiter, through "holes" in its atmosphere (holes in the sense of places where heat energy is emerging in greatest abundance). Like Earth, Jupiter harbors within its mass heat trapped since its formation, around 5 billion years ago. On Earth, the heat leaks out slowly through the crust, but in greater amounts through volcanoes, thermal vents, geysers, and the like. On giant gaseous Jupiter, heat escapes through convection of its atmospheric gases—like when soup bubbles on the stove.

How's it done? How do you fly a telescope on an airplane and keep it pointing on its target? In brief: shock absorbers, compressed air, electromagnetic motors, and tracking stars through a video camera.

SOFIA flies from its home base of Palmdale, California, near NASA's Dryden Flight Research Center.

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