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Infrared Astronomical Satellite

IRAS beside some of its all-sky images
Mission type	Infrared space observatory
Operator	NASA NIVR SERC
COSPAR ID	1983-004A
SATCAT no.	13777
Website	irsa.ipac.caltech.edu/Missions/iras.html
Mission duration	Final: 9 months, 26 days
Spacecraft properties
Manufacturer	Ball Aerospace Fokker Space Hollandse Signaal
Launch mass	1,083 kg (2,388 lb)
Dimensions	3.60 × 3.24 × 2.05 m (11.8 × 10.6 × 6.7 ft)[1]
Start of mission
Launch date	25 January 1983, 21:17 (1983-01-25UTC21:17) UTC[3]
Rocket	Delta 3910
Launch site	Vandenberg SLC-2W
Entered service	9 February 1983[2]
End of mission
Disposal	Decommissioned
Deactivated	21 November 1983 (1983-11-22)[3]
Orbital parameters
Reference system	Geocentric
Regime	Sun-synchronous
Semi-major axis	7,270.69 km (4,517.80 mi)
Eccentricity	0.001857
Perigee	879.05 km (546.22 mi)
Apogee	906.05 km (562.99 mi)
Inclination	98.95 deg
Period	102.8 min
Mean motion	14.00 rev/day
Epoch	19 November 2016, 04:15:30 UTC[4]
Main telescope
Type	Ritchey–Chrétien[5]
Diameter	57 cm (22 in)[5]
Focal length	545 cm (215 in), f/9.56[5]
Collecting area	2,019 cm2 (312.9 sq in)[5]
Wavelengths	Long-wavelength to far-infrared
Instruments SA Survey Array LRS Low Resolution Spectrometer CPC Chopped Photometric Channel

The Infrared Astronomical Satellite (IRAS) was the first-ever space telescope to perform a survey of the entire night sky at infrared wavelengths.^[6]

Launched on 25 January 1983,^[3] its mission lasted ten months.^[7] 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.^[7]

Support for the processing and analysis of data from IRAS was contributed from the Infrared Processing and Analysis Center at the California Institute of Technology. Currently, the Infrared Science Archive at IPAC holds the IRAS archive.^[8][9]

The success of IRAS led to interest in the 1985 Infrared Telescope (IRT) mission on the Space Shuttle, and the planned Shuttle Infrared Telescope Facility which eventually transformed into the Space Infrared Telescope Facility, SIRTF, which in turn was developed into the Spitzer Space Telescope, launched in 2003.^[10] The success of early infrared space astronomy led to further missions, such as the Infrared Space Observatory (1990s) and the Hubble Space Telescope's NICMOS instrument.

Mission

Launch of IRAS in 1983

False color image of comet IRAS–Araki–Alcock by IRAS

Infrared all-sky survey by IRAS

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 micrometers, with resolutions ranging from 30 arcseconds at 12 micrometers to 2 arcminutes at 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 planetary system formation. New discoveries included a dust disk around Vega and the first images of the Milky Way's core.

IRAS's life, like that of most infrared satellites that followed, was limited by its cooling system. To effectively work in the infrared domain, a telescope must be cooled to cryogenic temperatures. In IRAS's case, 73 kilograms (161 lb) of superfluid helium kept the telescope at a temperature of 2 K (−271 °C; −456 °F), keeping the satellite cool by evaporation. The on-board supply of liquid helium was depleted after 10 months on 21 November 1983, causing the telescope temperature to rise, preventing further observations. The spacecraft continues to orbit the Earth.

IRAS was designed to catalog 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 10P/Tempel. 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.^[7]

Discoveries

The observatory made headlines briefly with the announcement on 10 December 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".^[11][12] Further analysis revealed that, of several unidentified objects, nine were distant galaxies and the tenth was "intergalactic cirrus".^[13] None were found to be Solar System bodies.^[13][14]

During its mission, IRAS (and later the Spitzer Space Telescope) detected odd infrared signatures around several stars. This led to the systems being targeted by the Hubble Space Telescope's NICMOS instrument between 1999 and 2006, but nothing was detected. In 2014, using new image processing techniques on the Hubble data, researchers discovered planetary disks around these stars.^[15]

Asteroid discoveries

Later surveys

Several infrared space 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 on 14 December 2009 aboard a Delta II rocket from Vandenberg Air Force Base. Known as WISE, the telescope provided results hundreds of times more sensitive than IRAS at the shorter wavelengths; it also had an extended mission dubbed NEOWISE beginning in October 2010 after its coolant supply ran out.

See also

• 
  Diffuse Infrared Background Experiment, a infrared sky survey on COBE (1989)


• Infrared astronomy


• List of asteroid-discovering observatories


• List of largest infrared telescopes


• List of minor planet discoverers § Discovering dedicated institutions


• Category:IRAS catalogue objects

References

Bibliography

• 
  Beichman, C. A.; Neugebauer, G.; Habing, H. J.; Clegg, P. E.; Chester, T. J., eds. (1988). Infrared Astronomical Satellite (IRAS): Catalogs and Atlases (PDF). Volume 1: Explanatory Supplement (2nd ed.). NASA Scientific and Technical Information Division.
  

External links

Wikimedia Commons has media related to Infrared Astronomical Satellite.

• 
  IRAS website by Caltech


• 
  IRAS Minor Planet Survey archive by the Planetary Science Institute


• 
  IRAS survey at WikiSky.org