NASA's flying telescope SOFIA in search of distant stars

However, unlike most of the space agency's telescopes, the Stratospheric Observatory for Infrared Astronomy or SOFIA as it is called is not in space — rather it flies around mounted in a Boeing 747 jet with a large door cut on the side for it to see out.
One reason why scientists chose to put the telescope on a plane is that the plane lands every day, says Alycia Weinberg, an astronomer at the Carnegie Institution for Science, who is in charge of planning observations on SOFIA.

The daily landings let researchers fix things or upgrade instruments, Weinberg said.
Plus, with no more space shuttle missions, fixing telescopes in space ranges is no more viable.

Another reason a flying telescope makes sense is that at 45,000 feet you're above most of the moisture in atmosphere. For astronomers, that's important, because water vapour makes viewing the sky at infrared wavelengths impossible. Like sounds that are too low or too high for human ears to hear, infrared wavelengths are light and the human eye cannot see.

But Weinberg said lots of things glow at infrared wavelengths like "the cocoons of dust that old stars give off as they go through their final stages of life".

Those cocoons of dust are where new stars come from.One of the things astronomers especially like to do with light from distant objects is put it through a spectrometer that can reveal the kinds of atoms and molecules that are in the light from whatever the telescope is pointed at.

David Neufeld, a professor of physics and astronomy at Johns Hopkins University, has big plans for one of SOFIA's spectrometers.

I'm looking for a small molecule composed of one sulfur atom and one hydrogen atom," Neufeld says.

"It's called mercapto, and it's never been seen before in the interstellar gas".
Neufeld will be observing a cloud of gas in the interstellar space between Earth and a patch of space with the memorable name W49N.The reason Neufeld is interested in mercapto radicals is that they form at certain temperatures.

"So if we see it, what it will tell us is that the clouds of interstellar gas that we are looking at, which are thought to be very, very cold, may have parts of them where it's been heated up to much higher temperatures," he says.

And that information will help explain how new stars form out of these clouds of gasNeufeld says if it's there, mercapto will show up as a line in a readout from the spectrometer.

"(We) may see nothing, the instrument may not work, but hopefully pretty quickly we'll see a hint of the line. So hopefully it will seem like a eureka moment, anyway," he says.
Neufeld was supposed to board SOFIA at Andrews Air Force Base outside Washington, DC but the night before the flight, the NASA press office called to cancel the trip.
John Gegosian said there were two reasons: "First, there's a cooling fan for the telescope that malfunctioned. The second reason was the weather".

It had been raining heavily all week in Washington and the forecast called for more. Flight rules say SOFIA cannot take off in a rainstorm because water might get into the telescope's sensitive equipment.

A few days later the fan was fixed, and last Tuesday night SOFIA was able to observe Neufeld's interstellar gas cloud.

Neufeld couldn't make it out to California for that flight, so he waited by his computer for an email with the results. It came right after the plane landed.

"It was immediately obvious that we had an absolutely clear detection of the mercapto radicals, so I was absolutely delighted," he says.

SOFIA is a Boeing 747SP (special short-bodied but long- distance model of the 747), which served as a commercial airliner for Pan Am and then United Airlines. The aircraft now carries a 17-ton, 100-inch (2.5-metre) diameter telescope built by the German aerospace agency DLR and its contractors.

The first test flight of the combined aircraft and telescope assembly happened on April 26, 2007.

Former shuttle astronaut, and Dryden's chief test pilot, Gordon Fullerton was in the captain's seat on that day.

During its expected 20-year lifetime, SOFIA will be capable of "Great Observatory" class astronomical science, providing astronomers with access to the visible, infrared and sub-millimeter spectrum with optimised performance in the mid-infrared to sub-millimeter range.

Stefan Heyminck, a project engineer for the telescope who came from the Max Planck Institute for Radio Astronomy in Germany, said the coolest thing so far about seeing SOFIA in flight was how the telescope performed during turbulence.

Though they were bouncing around in their seats, Heyminck said, he was still seeing perfectly clear data on his laptop.

The whole telescope assembly sits on a ball bearing that's swimming on an oil film and when balanced with counter weights, it can be moved by just the touch of a finger. This allows it to move independent of the aircraft.

"(When) the aircraft is bouncing around, the telescope doesn't follow," Heyminck said.
Motors compensate for the aircraft movement to keep the telescope steady even during heavy turbulence.

Though SOFIA has flown some science missions already, including one that returned new data about stars in the constellation Orion, it is still under development.

The airborne observatory should be fully operational by 2014 and is expected to have at least a 20-year lifespan.