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IRAS, a.k.a. the Infrared Astronomical Satellite was the first space based observatory to perform an all survey in the infrared wavelengths. IRAS was launched on January 25, 1983 and lasted ten months. The observatory covered 96% of the sky four times and over 350,000 sources were observed within the 12, 25, 60, and 100 um. Resolutions ranged from 30 arcseconds at 12 um to 2 arcminutes at 100 um.
Many of the source found have still not been identified, but 75,000 are believed to be starburst galaxies still undergoing star formation. Many others are thought to stars in the early stages of planet formation. Notable discoveries include a dust disk around the star Vega, the first images of the Milky Way galaxy’s core, three asteroids, and six comets. The asteroid 3200 Phaethon and the comets 126P/IRAS and IRAS-Araki-Alcock were among the discoveries.
An infrared telescope must be cooled to cryogenic temperatures in order to work effectively, so IRAS’s longevity was limited by its cooling system. 73 kilograms of helium in a superfluid state was used to cool the onboard telescope to 2 K; thus cooling the unit through evaporation. Once the coolant was completely depleted, the telescope became unusable, but it still orbits the Earth.
Since the end of the IRAS mission, several space infrared telescopes have expanded its study of the Universe,. The Infrared Space Observatory, Spitzer Space Telescope, and the Wide-field Infrared Survey Explorer(WISE) are just a few.
If you’d like more info on the Infrared Astronomical Satellite, check out these articles:
Introduction to the Infrared Astronomical Satellite (IRAS)
StarChild: Infrared Astronomy Satellite (IRAS)
We’ve also recorded an entire episode of Astronomy Cast all about Infrared Astronomy. Listen here, Episode 132: Infrared Astronomy.