ISO in flight performance

ESA's Infrared Space Observatory, ISO, has ended its observational phase, long after the expiry date of the end of May 1997 foreseen in the specifications for the mission. Instead of the required Is months, the astronomers have been able to use ISO for more than 28 months, and as a result have gathered a wealth of additional information about the Universe. Altogether ISO has made over 26,000 observations of cosmic objects. ISO was the first cryogenically cooled astronomical space observatory. It provided unprecedented scientific information about our universe, its composition and evolution. The satellite in orbit performance turned out to be well within specifications. The robustness of the design allowed the scientific mission to continue long after the nominal end of life.