Sarah experiences a SOFIA calibration flight

Posted by Sarah Scoles
on Wednesday, June 19, 2013

Between 8:30 p.m. and 5:30 a.m. PDT last night (this morning), SOFIA, scientists, engineers, educators, and I took a trip over the Pacific and into both Canadian and Mexican airspace — no passport required, as if I had taken a step back in time.

Takeoff time. // all images by Sarah Scoles
Hopping aboard SOFIA is also like jumping back in time, as the cut-open Pan Am jet that houses the telescope is from the 1970s and still has ashtrays in the lavatories. But as soon as the astronomical equipment is on, it becomes clear that this is a plane of the cutting-edge present.

After the pre-flight briefing — which included late-breaking atmospheric water-vapor maps and minute-by-minute flight plans — all 22 passengers headed onto the NASA tarmac and into the belly of the jet.

Inside, we all donned wired headsets, and the two other Airborne Astronomy Ambassadors and I tuned in to every channel at once, sticking our own chatter to the “local” channel that only we could hear so that no one would have to listen to us respond to each other with, “Ten-four, over and out.”

Ready for entry.
Systems Engineer Marty Hench came over to us, pointed at a hatch in the floor, and informed us that if we ever needed to escape a 747 quickly, “Your best bet is this hatch.” It's affectionately known as the “hell hole,” and I will never be escaping through it.

This was the last commissioning flight for the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST). The telescope points out the open hole in the fuselage, but it's separated (thankfully) from the rest of the plane by a sealed wall that allows normal pressure and oxygen on its other side, where people who need to breathe are. SOFIA collects infrared photons that bounce from its mirrors into a tube that feeds into whatever instrument is on the people-side of the plane.

FORCAST is a two-channel camera that is best at researching the center of the Milky Way, dust clouds, and star formation — all places where infrared radiation, which humans perceive as heat, plays a significant role.

FORCAST is mounted on the tilting blue area in the background.
I'm going to jump ahead in my story to relay a joke I heard over the headset around 1 a.m., when an astronomer was expressing a desire to know the score of the Spurs-Heat basketball game. “I'm not a Spurs fan,” he said. “I'm just an anti-Heat fan.” Someone responded, “That's irony.”

But back to chronology. The plane climbed faster and higher than it would have on a commercial flight, and we were sitting backward, pushed into our '60s-era, steam-punk seat belts instead of into our seat backs. Everyone was anxious for this flight to go well. The one a few days ago ended prematurely when a dubious reading from one of the plane's 4,000 sensors sent it back to base with its head hung. Before it could land, though, it had to dump 128,000 pounds of fuel, lest it be too heavy to come to a nice stop. But last night, if all went well, this flight would mean the end of testing and calibration and the beginning of full-on scientific research with FORCAST.

SOFIA pointed at four bright stars, each at different heights above the horizon and thus different stratospheric altitudes for the plane, to make sure the telescope and FORCAST behaved as expected.

Astronomers love their data.
When SOFIA is locked on a target, the plane flies at a certain “heading,” a straight path that keeps the target in the telescope's range of movement. While the astronomers and engineers chattered back and forth like starship commanders on a sci-fi show, we (and they) could see a display of the telescope's view, but in visible light instead of infrared. This way, the teams can make sure SOFIA actually is pointing at a real object. When the plane is traveling between targets, it turns and climbs or dips according to where the next object is. Consequently, the visible-light view on our screens showed stars “streaking by and slipping around,” in the words of Hench. If you are being unscientific, it can look like an old-fashioned conception of what “warp drive” looks like from a spaceship's bridge.

SOFIA, while it doesn't have warp speed capabilities beyond those of a regular commercial jet, does contain electronics rated from 0°–160° Celsius and up to 2G. They were shaken and stirred and baked and frozen at these extremes for 20 minutes. Luckily, on this flight, we didn't have to push their capabilities.

But the good thing about having an airborne observatory that comes back to Earth is that any of these parts could be replaced should they start to act iffy. Screw loose? Turn it clockwise. Short circuit? Pull it out and pop in a new one. (Kepler space telescope, admit it: You are a little bit jealous right now, even though you get to be in orbit.)

Two astronomers watch over FORCAST.
And then, as importantly, SOFIA can be upgraded. The project is over 15 years in the making. A decade and a half ago, computers looked like Legos and the Internet was a slow thing that only nerds had. If SOFIA is to continue 20 years into the future, as is the plan, the program will have to continue to evolve as it has over the past 15. Instruments like FORCAST can be popped off and new, different ones snapped on in their place (like Legos), without anyone having to put on a spacesuit.

If tonight's flight is any indication, though, they would have to put on a jumpsuit, an equally bold fashion statement.

FYI, I'm writing this at the end of the flight, on which FORCAST performed like a champ and is ready to do some astronomy. The commissioners achieved as much on the first legs of this flight as they have on the past four flights. I think that my fellow Ambassadors and I must be good luck charms.

Regardless, as Jim DeBuizer, a lead SOFIA scientist, said to his team, “I hope you're ready for science.”

Stay tuned.

Related blogs:
Sarah preps for flights on SOFIA

Sarah takes a trip on SOFIA, the flying infrared observatory

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