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 the United States (NASA), the Netherlands (NIVR), and the United Kingdom (SERC).

IRAS mapped 96% of the sky four times, at 12, 25, 60 and 100 micrometre wavelengths. It discovered about 500,000 sources, many of which are still awaiting 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, possibly the early stage of a planetary system formation. New discoveries included a dust disk around Vega and the first images of the Milky Way Galaxy's core.

IRAS's 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 kelvins (about −272 °C). The fluid keeps the satellite cool by evaporation. When the fluid totally evaporated, the satellite temperature rose preventing further observations.

Today (2004), the Spitzer Space Telescope is the best infrared telescope, allowing astronomers to follow up many detections first made by IRAS.

See also: telescope, space telescope.

In addition to its main work, IRAS also discovered three asteroids, including notably 3200 Phaethon (an Apollo asteroid and the parent body of the Geminid meteor shower), as well as the periodic comet 126P/IRAS .

External links

• NASA IRAS page
• Caltech IRAS page
• Ball Aerospace IRAS page