IRAS
The Infrared Astronomical Satellite (IRAS) was a space-based observatory that performed a survey of the entire sky at infrared wavelengths.Launched in January 25, 1983, its mission lasted ten months. It was a joint project of US, UK and the Netherlands.
IRAS mapped 96% of the sky four times, at 12, 25, 60 and 100 microns wavelengths. It discovered about 500,000 sources, many of which are still waiting identification. About 75,000 of those are believed to be starbust galaxies, still enduring their star-formation stage. Many other sources are normal stars with disks of dust around them, possibily the early stage of a planetary system formation.
IRAS life, like most of infrared satellites, was limited by its cooling system: to effectively work in the infrared domain, a satellite must be cooled to impressively low temperatures. In IRAS' case, 720 liters of superfluid helium kept the satellite at a temperature of 1.6 Kelvin (about -272 °C). The fluid keeps the satellite cool by evaporation. When the fluid is totally evaporated, the satellite temperature starts to rise and observations must cease.
