Model of the SOFIA (Stratospheric Observatory for Infrared Astronomy) telescope mounting and mirror. SOFIA is a 2.5-metre infrared telescope that is flown in its 747SP 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. Observations also occur in the sub-millimetre wavelength range. SOFIA is a joint project of the German Aerospace Center (DLR) and NASA. It is operated by the Deutsches SOFIA Institut (DSI) at the University of Stuttgart. The first observations took place in May 2010.