On this mission, SOFIA is setting out to study Titan, Saturn’s biggest moon, by flying into the faint shadow that it casts as it blocks the light from a faraway star. It’s a phenomenon called an occultation, and if the mission succeeds, it will reveal new details about Titan’s atmosphere.

SOFIA is a very unusual observatory. It is a 747 aircraft with a hatch in the side, which opens in flight to reveal a large, custom-built telescope – carefully engineered to work inside a moving jet plane. Its full name is the Stratospheric Observatory for Infrared Astronomy, and it’s a joint project of Nasa and the German space agency, DLR.

(Photo: SOFIA is a heavily modified 747SP which was acquired by Nasa in the mid-1990s after spending 20 years as a passenger jet. (Credit: Wayne Williams)