NASA's flying observatory is a jet with a 17-tonne telescope

NASA has fitted a heavily modified Boeing jet with a 17-tonne telescope and will use it as a flying observatory to study how stars are formed.
Officially known as the Stratospheric Observatory for Infrared Astronomy, SOFIA is a heavily modified Boeing 747 Special Performance jetliner, with a 17-tonne, 8-foot telescope mounted behind a 16-by-23-foot sliding door that reveals the infrared telescope to the skies.
The plane's ability to fly near the edges of the atmosphere gives it better visibility than ground-based observatories, 'wired.Com' reported.
The 747SP was designed by Boeing in the 1970s to fly faster, higher, and farther than other versions of the 747. The company's engineers shortened the fuselage by 55 feet to cut weight, but left the power plants intact.

The plane can stay airborne for over 12 hours and its range is 6,625 nautical miles.
It can fly above the troposphere and 99.8 per cent of the water vapour held in our atmosphere, which obscures infrared light.

That gives its on-board infrared telescope a clear view into outer space.
According to NASA, the data provided by SOFIA "cannot be obtained by any other astronomical facility on the ground or in space."
Unlike grounded telescopes and satellites fixed in orbit, SOFIA is mobile, so it can better spot transient space events like supernovae and comets.
Currently SOFIA is in Germany for extensive maintenance and refitting. This is the last step in NASA's rollout of SOFIA and scientists plan to run 100 observation flights with her in 2015.