Submillimetre observations of these dark clouds can be used to determine chemical abundances and cooling mechanisms for the molecules which comprise them.
The ideal submillimetre observing site is dry, cool, has stable weather conditions and is away from urban population centres.
[1][2] The Llano de Chajnantor Observatory site hosts the Atacama Pathfinder Experiment (APEX), the largest submillimetre telescope operating in the southern hemisphere, and the world's largest ground based astronomy project, the Atacama Large Millimeter Array (ALMA), an interferometer for submillimetre wavelength observations made of 54 12-metre and 12 7-metre radio telescopes.
The Submillimeter Array (SMA) is another interferometer, located at Mauna Kea, consisting of eight 6-metre diameter radio telescopes.
[citation needed] 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.