The Infrared Space Observatory
ESA's Infrared Space Observatory (ISO) is an astronomical satellite that was operational between November 1995 and May 1998. It operated in the infrared range of the electromagnetic spectrum at wavelengths from 2.5 to 240 microns, invisible to the human eye and to optical telescopes. Our atmosphere stops most infrared wavelengths - preventing them from reaching the ground - and this is why a space telescope is needed to detect this kind of radiation.
Why observe in the infrared?
Infrared radiation is primarily 'heat', or thermal radiation. Even objects that we think of as being very cold, such as an ice cube, emit infrared radiation.
For this reason ISO could observe astronomical objects that remain hidden for optical telescopes, such as cool objects that are unable to emit in visible light. Opaque objects, those surrounded by clouds of dust, are another specialty of ISO because the longer IR wavelengths can penetrate the dust, allowing us to see deeper into such clouds.
An observation every 32 minutes
On average, ISO performed 45 observations per revolution (a period of almost 24 hours). Throughout all of its lifetime - more than 900 revolutions - ISO successfully completed well over 26 000 scientific observations.
Infrared Space Observatory (ISO's official homepage)
About the mission (ESA)
2nd August 2000