A highly modified Boeing 747SP jet carrying a 17-ton telescope for astronomy research landed at Hamburg Airport on Saturday to undergo extensive maintenance. Known as SOFIA (Stratospheric Observatory for Infrared Astronomy), the plane is a joint project of NASA and the German Aerospace Center (DLR).
SOFIA (tail number N747NA) is stationed in Palmdale, Calif., near NASA's Armstrong Flight Research Center at Edwards Air Force Base. From now until the beginning of November, the aircraft and its telescope will be undergoing extensive maintenance at the Hamburg facilities of Lufthansa Technik.
DLR and NASA have selected Lufthansa for the overhaul of the aircraft because they have the world's longest and most extensive experience with maintaining aircraft of this type.
There were 45 Boeing 747SPs built, 18 of which are still in use. Boeing itself, however, no longer supports this aircraft type. U.S.-based companies with a license for extensive maintenance and repair do not have comparable experience. The previous U.S. operators of this aircraft, Pan Am, who brought the aircraft into service as 'Clipper Lindbergh' in 1977, and United Airlines, who purchased the plane in 1986, also no longer perform maintenance on this type of aircraft, and, as they are no longer operating the 747SP, they have let their licenses lapse. The SP in 747SP stands for 'Special Performance.' The aircraft has a much shorter fuselage but the same power; these aircraft can therefore fly significantly higher than other versions.
SOFIA is a unique airborne observatory, which, since 2010, has made around 90 scientific flights to study the development of galaxies and how stars and planetary systems are formed from molecular and dust clouds.
In contrast to space observatories, continuously improved or even newly developed instruments can be used and the latest technology can be implemented on SOFIA. This airborne observatory performs almost like a space observatory, but it returns to Earth after each flight. Because SOFIA flies in the stratosphere, above the water vapor in the atmosphere, it can observe infrared radiation with virtually no losses. Ground-based telescopes are not able to measure this radiation from space, as the water vapor blocks most of the infrared radiation.
The German SOFIA Institute at the University of Stuttgart has been charged with the coordination of the DLR operating contribution. While the aircraft is undergoing its overhaul in Hamburg, DSI personnel will take the opportunity to also perform thorough maintenance on the telescope. "We will replace worn parts and improve its functionality," says DSI Director Thomas Keilig.
The specifications of the aircraft also influence its treatment in the maintenance facility: "We must, for example, first lift SOFIA to a height of six meters to replace the landing gear,” says Sven Hatje, the project manager responsible for the SOFIA overhaul program. “The rear of the aircraft is, with its weight of 48 tons, too heavy for conventional lifting methods. This is why we will have to jack SOFIA up with five instead of three lifters. For this, we have to obtain a special permit."
Looking to the future, Eddie Zavala, SOFIA program manager at NASA says: "On May 29, we formally completed the development phase and NASA declared SOFIA fully operational. After the overhaul here in Hamburg, SOFIA will be resuming operations in 2015 with approximately 100 planned observation flights per year for many years to come and it will be a unique scientific tool for infrared astronomers."