SCUBA introduction
03 May 2011



SCUBA Introduction




SCUBA, the Submillimetre Common-User Bolometer Array, was designed and constructed at the Royal Observatory, Edinburgh in collaboration with Queen Mary, University of London. It was delivered to the James Clerk Maxwell Telescope (JCMT (link opens in a new window)) in Hawaii in 1996 and was fully operational by 1997.

The JCMT views the sky in the submillimetre region of the spectrum. At these wavelengths, the telescope can detect objects in the dusty regions in space that would normally be obscured at visible wavelengths. Because the wavelength of radiation is related to the temperature of its source, submillimetre measurements can reveal something about cooler objects in space, like interstellar dust.

Unlike previous submillimetre instruments used at JCMT SCUBA is an imaging device which can act as a camera and a photometer. It was a substantial improvement over previous submillimetre instruments, both in sensitivity and productivity, with more than 20 times the sensitivity of its nearest competitor.

SCUBA has two arrays of bolometric detectors, or pixels. The long-wave array has 37 pixels operating in the 750 and 850 micrometre atmospheric transmission windows, while the short-wave array has 91 pixels for observations at 350 and 450 micrometres. The pixels are arranged in a close-packed hexagon arrangement. Both arrays have approximately the same field-of-view with a diameter of 2.3 arc-minutes, and can be used simultaneously by means of a beam-splitter. There are also three pixels available for photometry in the transmission windows at 1.1, 1.35 and 2.0 mm, and these are located around the edge of the long-wave array. The detectors are cooled to approximately 100mK (just above absolute zero or -273 degrees C) to limit background noise from heat emitted by the instrument.

A 2001 survey by the US-based Space Telescope Science Institute revealed that scientific results from SCUBA have been cited almost as often as those from the Hubble Space Telescope, and much more so than those from any other ground-based facility or satellite project. Given that SCUBA is only an instrument and not a telescope this is an amazing testament to the SCUBA concept and its engineering. It continues to be in great demand for use by the international astronomical community.

SCUBA 2, a second generation instrument is already being planned by the UK ATC in collaboration with international partners.

For more technical information about SCUBA please visit the JCMT website (link opens in a new window).