IRAS

IRAS

(ÿ -rass) Abbrev. for Infrared Astronomical Satellite. A satellite that has made an all-sky survey in the infrared wavelength range 10–100 μm using liquid helium-cooled optics and detectors. The project was developed and operated by the Netherlands Agency for Aerospace Programs (NIVR), NASA, and the UK Science and Engineering Research Council (SERC). The satellite was launched into a 900 km orbit on Jan. 26 1983 and operated until Nov. 22 1983 when the helium supply was exhausted. By the end of the mission 95% of the sky had been surveyed with confirming scans, 3% surveyed only once, and the remaining 2% not surveyed at all.

IRAS consists of a spacecraft that pointed a liquid helium cryostat containing a 0.57-meter Ritchey–Chrétien telescope cooled to less than 10 K. An array of cooled detectors was located in the focal plane at the Cassegrain focus of the telescope. The 62 photoconductive detectors responded to one of four wavebands centered on 100, 60, 25, or 12 μm. They were arranged so that every source crossing the field of view could be seen by at least two detectors in each of the wavebands. The low resolution spectrometer (LRS) covered the range 8–23 μm with a spectral resolution, λ/δλ, of about 20. The chopped photometric channel (CPC) mapped infrared sources on a 9 × 9 arcmin raster at 50 and 100 μm with a spatial resolution of about 1 arcmin.

The operation center for the satellite was at the SERC Rutherford-Appleton Laboratory, near Oxford, England where a preliminary analysis of the data was made. The final reduction of data was done in the USA and the Netherlands. The IRAS data has been issued in various catalogs, including the IRAS Point Source Catalog (IPSC) and the IRAS Faint Source Survey (IFSS) and corresponding catalog (IFSC). The IRAS Sky Survey Atlas (ISSA) for ecliptic latitude over 50° was released on CD–ROM in 1992 the remainder scheduled in 1994.

The results obtained so far relate to almost every aspect of astronomy. Some of the highlights are: the discovery of a dust shell around Vega, which may be an early planetary system; the discovery of infrared cirrus in our Galaxy; the first detection from space using infrared of comets (IRAS discovered 5 new comets); the detailed mapping of the infrared emission from the galactic plane; observations on galaxies showing that most of the galaxies detected in the 60- and 100-μm wavebands are spirals; observations on low-luminosity protostars in several molecular cloud complexes.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006