IRAS beside some of its all-sky images
|Organization||NASA / NIVR / SERC|
|Major contractors||Ball Aerospace / Fokker Space / Hollandse Signaal|
|Launch date||25 January 1983|
|Launch site||SLC-2 West, Vandenberg AFB, California, U.S.|
|Launch vehicle||Delta 3910|
|Mission length||10 months|
|Type of orbit||sun-synchronous polar orbit|
|Orbit height||900 km|
|Orbit period||100 minutes|
|Location||in orbit, deactivated|
|Wavelength||Long-wavelength to far infrared|
|Collecting area||0.202 m2|
|Focal length||5.5 m, f/9.6|
|Main array||62 detectors|
|Low Resolution Spectrometer (LRS)||8 to 22 µm slitless spectrometer|
|Chopped Photometric Channel (CPC)||low-quality mapping|
Launched on January 25, 1983, its mission lasted ten months. The telescope was a joint project of the United States (NASA), the Netherlands (NIVR), and the United Kingdom (SERC). Over 250,000 infrared sources were observed at 12, 25, 60, and 100 micrometer wavelengths.
IRAS was the first observatory to perform an all-sky survey at infrared wavelengths. It mapped 96% of the sky four times, at 12, 25, 60 and 100 micrometres wavelengths, with resolutions ranging from 30 arcseconds at wavelength 12 micrometers to 2 arcminutes at wavelength 100 micrometers. It discovered about 350,000 sources, many of which are still awaiting identification. About 75,000 of those are believed to be starburst 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 that of most of infrared satellites that followed after, was limited by its cooling system. To effectively work in the infrared domain, the telescope must be cooled to cryogenic temperatures. In IRAS's case, 73 kilograms of superfluid helium kept the telescope at a temperature of 2 kelvins (about -271 °C), keeping the satellite cool by evaporation. The on-board supply of liquid helium was depleted after 10 months on November 22, 1983, causing the telescope temperature to rise, preventing further observations. The spacecraft continues to orbit close to the earth.
IRAS was designed to catalogue fixed sources, so it scanned the same region of sky several times. Jack Meadows led a team at Leicester University, including John Davies and Simon Green, which searched the rejected sources for moving objects. This led to the discovery of three asteroids, including 3200 Phaethon (an Apollo asteroid and the parent body of the Geminid meteor shower), six comets, and a huge dust trail associated with comet Tempel-2. The comets included 126P/IRAS, 161P/Hartley-IRAS, and comet IRAS-Araki-Alcock (C/1983 H1), which made a close approach to the Earth in 1983. Out of the six comets IRAS found, four were long period and two were short period comets.
The observatory made headlines briefly with the announcement on December 10, 1983 of the discovery of an "unknown object" at first described as "possibly as large as the giant planet Jupiter and possibly so close to Earth that it would be part of this solar system." Further analysis revealed that, of several unidentified objects, nine were distant galaxies and the tenth was "intergalactic cirrus". None were found to be Solar System bodies.
Several space infrared telescopes have continued and greatly expanded the study of the infrared Universe, such as the Infrared Space Observatory launched in 1995, the Spitzer Space Telescope launched in 2003, and the AKARI Space Telescope launched in 2006.
A next generation of infrared space telescopes began when NASA's Wide-field Infrared Survey Explorer launched December 14, 2009 aboard a Delta II rocket from Vandenberg Air Force Base in California. Known as WISE, the telescope provided results hundreds of times more sensitive than IRAS at the shorter wavelengths, and also had an extended mission into 2011 even after its coolant supply ran out.
|3200 Phaethon||October 11, 1983|
|3728 IRAS||August 23, 1983|
|(10714) 1983 QG||August 31, 1983|
- IRAS Explanatory supplement, Telescope Overview, Optics.
- IRAS Explanatory Supplement II. Satellite Description IPAC IRAS archive
- Lutz D. Schmadel - Dictionary of minor planet names (2003) - Page 315 (Google Books)
- Thomas O'Toole (1983-12-30). "Mystery Heavenly Body Discovered". Washington Post. p. A1. Archived from the original on 2010-02-01. Retrieved 2008-01-28.
- "Mystery heavenly body found close to Earth". The Gazette. Washington Post. 1983-12-30. p. A-2. Retrieved 2012-10-16.
- Thomas J. Chester. "No Tenth Planet Yet From IRAS". Thomas J. Chester (CalTech). Archived from the original on 2010-02-02. Retrieved 2008-01-28.
- Phil Plait (2010-11-17). "The Planet X Saga: Science". Bad Astronomy. Retrieved 2011-03-05.
|Wikimedia Commons has media related to Infrared Astronomical Satellite.|
- Caltech IRAS page
- IRAS survey on WikiSky
- Archive of IRAS Minor Planet Survey (IMPS)
- Ophiuchus dust clouds