ISO: highlights of recent results Original Research Article

The Infrared Space Observatory (ISO) was the world’s first true orbiting infrared observatory. Equipped with four versatile scientific instruments, it was launched by an Ariane 44P in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the universe at infrared wavelengths (2.5–240 μm). Its 60-cm diameter telescope was cooled by superfluid liquid helium to temperatures of 2–4 K. The mission was a great technical, operational and scientific success, with most satellite sub-systems operating far better than specifications, while the scientific instruments returned unprecedented results ensuring that its scientific output impacted practically all fields of astronomy. During its routine operational phase, which lasted until April 1998 – almost a year longer than specified, ISO successfully made some 30,000 individual imaging, photometric, spectroscopic and polarimetric observations ranging from objects in our own solar system right out to the most distant extragalactic sources. ISOs data archive – – opened to the community in December 1998 and, including data from calibration and auxiliary mode observations, contains about 150,000 data sets. Since 1996 to date about 1000 ISO papers have been published in the refereed literature, and many more in conference proceedings. A summary of the mission – including some of its highlights – is presented, followed by a description of current and future activities.