Infrared Space Observatory

The Infrared Space Observatory (ISO) is a European Space Agency (ESA) satellite that was operational between November 1995 and May 1998. The ISO space telescope operated at wavelengths from 2.5 to 240 microns, in the infrared range of the electromagnetic spectrum. Because the atmosphere blocks most infrared wavelengths, a space telescope is needed to detect this kind of radiation. The satellite consists of a large liquid-helium cryostat, a telescope with a 60-cm diameter primary mirror, four scientific instruments, and the service module. The ISO is 5.3 meters high, 3.6 meters wide, and 2.8 meters deep. At launch it weighed 2400 kilograms.

The ISO was launched into orbit by an Ariane 44P from Europe's spaceport in Kourou, on November 17, 1995.