SOFIA airborne observatory telescope, cradled in its framework inside the telescope cavity in the SOFIA aircraft during its test flight phase. 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 Centre (DLR). The first observations took place in May 2010.