A Tour of NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA)

I enjoyed a tour of NASA's Stratospheric Observatory for Infrared Astronomy (SOFOA), which was on display at Moffett Field near San Francisco this weekend.  The aircraft is a Boeing 747SP modified to carry a telescope in its fuselage. SOFIA is a joint project of NASA and the German Aerospace Center (DLR)

The heart of SOFIA is a 2.5 meter (100 inch) Bent Cassegrain/Nasmyth telescope built in Germany.  It needs to be flown to high altitude, above most of the infrared absorbing water vapor in the atmosphere, to function.  The telescope can collect data at infrared wavelengths between 0.3 and 1600 microns. It's hoped that the lower limit will be pushed to 1.5 microns soon. Peering perpendicular to the direction of flight the telescope has a range of motion of + 15 to + 70 degrees above the horizon and can move about + or - 3 degrees fore and aft to correct for the motion of the aircraft.

Interchangeable instruments can be mounted to the telescope.  One of these is the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST). FORCAST is a mid-infrared camera that records images at infrared wavelengths of 5 to 40 microns that are used to study celestial objects such as planets and star forming regions.

FORCAST being installed in SOFIA - NASA
George Gull, a Cornell University research support specialist and now lead engineer for the FORCAST infrared camera talked with me a few minutes about SOFIA and FORCAST.  

First, he said, the research flights are marathons, normally lasting 10 hours.  The aircraft inatally climbs to 35,000 feet, instruments are adjusted and observations made.  As fuel burns off, reducing the weight of the aircraft, SOFIA will climb to 39,000 feet, instruments are readjusted and more observations made. Finally the aircraft climbs to 45,000 feet and the cycle is repeated.

Secondly, the FORCAST instrument is cooled to 3 degrees kelvin by liquid helium and can detect temperatures as low as about 30 degrees kelvin, which means it can see very faint infrared sources.  

Thanks Mr. Gull for taking the time to speak so enthusiastically to that continuous line of visitors. It was the highlight of my day.  That's him wearing the blue shirt in the photo by the way. 

SOFIA's flightplans are carefully designed to maximize observing time.  Area's of the sky move out of view as the earth rotates or the aircraft turns.  Careful planning can mean up to 8 hours observing time on a single flight. A planned future flight path from New Zealand to Australia will allow SOFIA to keep the center of our Milky Way Galaxy in view for 10 continuous hours. 

One of the major advantages of SOFIA over ground based observatories is that it can move to where the action is.  This was demonstrated recently when the aircraft flew 1800 miles out over the Pacific Ocean from its base in Southern California to position itself in the center of the dwarf planet Pluto's shadow's as it eclipsed a distant star. It was the only observatory capable of doing so.

I also got a chance to talk to one of the pilots and asked him how the aircraft behaved when the door opened.  He said the aerodynamics of the door were so well designed that there was no difference in the planes handling characteristics. 

Here are some fun facts about the 747SP that became SOFIA:
  • It was delevered to Pan American Airlines in May of 1977 and christened "Clipper Lindbergh" by Anne Morrow Lindbergh on the 50th year anniversary of Charles A Lindbergh's solo flight across the Atlantic.
  • In 1986 it was sold to United Airlines after the bankruptcy of Pan Am. 
  • In 1989 the above mentioned George Gull, just happened to notice the "Clipper Lindbergh" insignia on his plane when he flew from Hong Kong to San Francisco, so he was actually the first member of the team to fly on the aircraft.
  • In 1995 it was retired and stored at the Las Vegas airport. 
  • NASA bought the aircraft in 1997 and moved it to Waco Texas for modification and installation of the telescope.  
  • It remained in Waco until the heavly modified plane finally flew again in 2007.  It's test pilot was former NASA astronaut Gordon Fullerton, who was 71 at the time.
  • And in a real touch of class by NASA, SOFIA was rechristened "Clipper Lindbergh" by Charles Lindbergh's grandson Eric Lindbergh in May of 2007.
  • On 5/25/2010 SOFIA made its "first light flight." 

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