Flying observatory SOFIA for major overhaul at Lufthansa Technik

Also thorough going over for the 17-ton telescope

SOFIA, a modified Boeing 747SP that is operated jointly by the USA's National Aeronautics and Space Administration (NASA) and the German Aerospace Centre (DLR) as a "Stratospheric Observatory for Infrared Astronomy", is undergoing a major overhaul at Lufthansa Technik in Hamburg. The DLR and NASA have selected Lufthansa Technik to perform a major overhaul of the aircraft on account of its claim to have the widest and longest experience at maintaining this aircraft type.

Explaining the background, Alois Himmes, SOFIA project manager at the DLR, says "Altogether there were 45 Boeing 747SP's, 18 of which are still in service. But Boeing itself does not maintain this aircraft type." None of the companies resident in the USA that are licensed to perform comprehensive maintenance and repairs has comparable experience. The 747SP "SP" stands for "Special Performance" has a significantly shorter fuselage but features the same performance, enabling it to fly a lot higher, up to an altitude of 12 to 14 kilometers, than the other versions.

SOFIA is the world's only flying observatory, and in the course of some 90 scientific flights carried out since 2010 it has, amongst other things, investigated how Milky Way systems develop and why stars and planetary systems developed out of interstellar molecular and dust clouds. Integrated into the fuselage is a 17-ton telescope with a mirror diameter of 2.7 meters that was developed in Germany and commissioned by the DLR space management. "Unlike space observatories, the technology used is not frozen, but improved or even newly developed instruments that incorporate the latest technology can always be deployed on SOFIA. SOFIA is like a space observatory, except that after every flight it returns to Earth," Himmes explains.

For Lufthansa Technik too, this check is unusual. As Sven Hatje, the Lufthansa Technik project manager responsible for the overhaul, explains, "Because SOFIA is not an airliner but a flying observatory, routine procedures are transformed into special operations." Over the next few months the engineers plan to examine SOFIA closely in five phases: arrival, inspection, modification, installation and acceptance. The aircraft specifications also affect its handling in the dock. "For example, we have to first raise SOFIA to a height of six meters in order to be able to replace the landing gear. But the rear end of the aircraft weighs 48 tons, making it too heavy for normal procedures. So we jack the aircraft up using five jacks instead of three. To do that we need special approval."

At the same time the research aircraft not only has modified electronics in the cockpit and extensive additional electronic systems, but and this is really unusual the fuselage incorporates a hatch approximately four meters by six that opens at night when the telescope is looking into the starry sky.

Staff of the German SOFIA Institute (DSI) will take the opportunity presented by the major overhaul of the jumbo in Hamburg to give the telescope a thorough going over. "We will replace parts subject to wear and tear and improve the functionality," explains DSI director Thomas Keilig. "We are looking forward to what is bound to be a productive collaboration with our colleagues from Lufthansa Technik."