submillimetre-wave astronomy

The study of electromagnetic radiation from celestial sources in the wavelength band between 0.3 and 3 millimetres. A combination of techniques from radio astronomy and infrared astronomy is required for this transition region of the electromagnetic spectrum. The telescopes have to be located at particularly dry places and high elevations, because water vapour in the Earth's atmosphere absorbs strongly at these wavelengths, and the astronomical signals are mostly weak. However, this region of the spectrum is important for a number of studies in astronomy, including cosmic background radiation, regions of star formation and spectral lines of molecules in interstellar clouds. There are only a few submillimetre telescopes in operation. One is the James Clerk Maxwell Telescope situated at the Mauna Kea Observatories, Hawaii. The California Institute of Technology's Submillimeter Observatory (CSO) - a 10.4-metre (84-foot) telescope with a segmented mirror is also at the same site. The Swedish-ESO Submillimetre Telescope (SEST) is at the European Southern Observatory (ESO), La Silla, Chile. The reflector has a diameter of 15 metres (49 feet) and consists of 176 panels that can be adjusted separately. The most recent to be built is the Heinrich Hertz Submillimeter Telescope at Mount Graham in Arizona. In 1997, the first orbiting observatory for submillimetre wave astronomy was launched from the USA - the Submillimeter Wave Astronomy Satellite (SWAS) - with the objective of studying the composition of interstellar clouds.