The James Clerk Maxwell Telescope (JCMT) is a submillimetre-wavelength telescope at Mauna Kea Observatory in Hawaii. Its primary mirror is 15 metres (16.4 yards) across: it is the largest astronomical telescope that operates in submillimetre wavelengths of the electromagnetic spectrum (far-infrared to microwave). Scientists use it to study our Solar System, interstellar dust and gas, and distant galaxies.
The JCMT is funded by a partnership between the United Kingdom, Canada, and the Netherlands. It is operated by the Joint Astronomy Centre and was named in honour of mathematical physicist James Clerk Maxwell.The telescope is near the summit of Mauna Kea at 13,425 feet (4092 m). It is part of the Mauna Kea Observatory. The JCMT has the second-largest telescope mirror on Mauna Kea. (The largest is the VLBA antenna.)This telescope was combined with the Caltech Submillimeter Observatory next to it to form the first submillimeter interferometer. This success was important in pushing ahead the construction of the Submillimeter Array and the Atacama Large Millimeter Array interferometers.
The JCMT has two kinds of instruments—broadband continuum detectors and heterodyne detection spectral line receivers.Continuum emission is a tracer of star formation in other galaxies and gives astronomers clues to the presence, distance, and evolution history of galaxies other than our own. Within our own galaxy dust emission is associated with stellar nurseries and planet forming solar systems.Spectral-line observations can be used to identify particular molecules in molecular clouds, study their distribution and chemistry and determine gas velocity gradients across astronomical objects (because of the doppler effect).
The older continuum single pixel UKT14 bolometer receiver was replaced in the 1990s by the Submillimetre Common-User Bolometer Array (SCUBA). The SCUBA project was greenlighted in 1987 by the JCMT board and was in development for nearly a decade before it saw first light on the telescope. While it was not the first bolometer-array it was "unique in combining an unparallel sensitivity with an extensive wavelength range and field-of-view".SCUBA operated simultaneously at wavelengths of 450 and 850 micron (with 91 and 37 pixels, respectively), and was sensitive to the thermal emission from interstellar dust. SCUBA is ranked second only to the Hubble Space Telescope in terms of publication of high-impact astronomical research. SCUBA was retired from service in 2005.
SCUBA-2, another continuum instrument, was commissioned in 2011. This ground-breaking camera consists of large arrays of superconducting transition edge sensors with a mapping speed hundreds of times larger than SCUBA. It has 5120 array elements at both 450 and 850 micron wavelength (10,240 total pixels). It has been conducting the JCMT legacy surveys since November, 2011, including the SCUBA-2 All Sky Survey, and was made available for general astronomical observations in February, 2012.Two ancillary instruments, FTS-2 and POL-2, add spectroscopic and polarimetric capabilities to SCUBA-2.
Spectral Line Detectors:
The JCMT is also equipped with three heterodyne receivers, which allow submillimetre spectral line observations to be made. The spectral-line mapping capabilities of the JCMT have been greatly enhanced by the commissioning of HARP-B, a 350 GHz, 16 element heterodyne array receiver. HARP-B, and the other heterodyne instruments, can be used in conjunction with the JCMT's new digital autocorrelation spectrometer, ACSIS.