After a series of brief studies by infrared instruments carried on sounding rockets had detected about 4,000 celestial sources of infrared radiation, the United States, the United Kingdom, and the Netherlands built IRAS to map the sky at infrared wavelengths of 12, 25, 60, and 100 micrometres. It was launched on Jan. 25, 1983, on a Delta rocket from Vandenberg Air Force Base in California into a polar orbit at an altitude of 900 km (550 miles).
Its 60-cm- (24-inch-) diameter telescope was cooled by superfluid helium that chilled the structure down to 10 K (−263 °C, or −442 °F) and the detector to 2 K (−271 °C, or −456 °F). This was necessary because if the telescope were not cooled down, its own thermal radiation at infrared wavelengths would swamp the much fainter radiation from astronomical objects.
(Figures 15- 16)
Figure 15: U.S.-U.K.-Netherlands Infrared Astronomical Satellite (IRAS), depicted in a cutaway model. Launched on Jan. 25, 1983, the Earth-orbiting observatory mapped the sky for 10 months at infrared wavelengths above the interference of Earth's atmosphere.