SOFIA airborne observatory in flight. Close-up of the SOFIA observatory's door in the 747SP aircraft during a flight to test the door opening mechanism. SOFIA is the Stratospheric Observatory for Infrared Astronomy. It is a 2.5-metre infrared telescope that is flown in an aircraft to the stratosphere, some 10-50 kilometres above sea level. This allows the detection of infrared light that is normally blocked by water vapour lower in the atmosphere. SOFIA was jointly developed from 1996 by NASA and the German Aerospace Center (DLR). The first observations took place in May 2010. Photographed on 18 December 2009.