Submillimetre astronomy

Submillimetre Astronomy is the branch of observational astronomy that is conducted at submillimetre wavelengths. Often descibed as residing between the infrared and radio wavebands, the submillimetre waveband more precisesly falls between the far-infrared and microwave wavebands, typically taken to be between a few hundred microns and a millimetre. (Note that the British English spelling is "submillimetre" while the American English spelling is "submillimeter").

Submillimetre Astronomy from the ground

The most significant limitation to the detection of astronomical emission at submillimetre wavelengths with ground based observatories is atmospheric emission, noise and attenuation. Like the infrared, the submillimetre atmosphere is dominated by numerous water vapour absorption bands and it is only through "windows" between these bands that observations are possible. The ideal submillimetre observing site is dry, cool, has stable weather conditions and is away from urban population centres. There are only a handful of such sites identified, they include Manuna Kea (Hawaii, USA), the Atacama Plateau (Chile), the South Pole, and Hanla (India). Comparisons show that all four sites are excellent for submillimetre astronomy, and of these sites Mauna Kea is the most established and arguably the most accessible.

Submillimetre Astronomy from space

Space-based observations at the submillimetre wavelengths remove the ground-based limitations of atmospheric absorption. The Submillimeter Wave Astronomy Satellite (SWAS) was launched into low Earth orbit on December 5, 1998 as one of NASA's Small Explorer Program (SMEX) missions. The mission of the spacecraft is to make targeted observations of giant molecular clouds and dark cloud cores. The focus of SWAS is five spectral lines: water, isotopic water, isotopic carbon monoxide, molecular oxygen, and neutral carbon.

The SWAS satellite was repurposed in June, 2005 to provide support for the NASA Deep Impact mission. SWAS will provide water production data on the comet until the end of August 2005.