ISO's orbital path

ESA's Infrared Space Observatory (ISO) was launched on 19 November 1995 as the world's first spaceborne infrared observatory. It provided an entirely fresh perspective on the Universe before it was switched off on 16 May 1998 - well beyond the planned 18-month life. ISO's highly elliptical orbit allowed the spacecraft to return data in real-time (there was no onboard recorder) to its main ground station at Villafranca, Spain for most of the 24h period. Although the supply of liquid helium, used to cool the telescope and instruments, ran out on 8 April 1998, the last scientific observation was not made until 10 May 1998. [Image Date: 1991/04] [91.04.001-021]