Caltech Submillimeter Observatory. The side of the Caltech Submillimeter Observatory (CSO). The domes in the background are the (from left to right): Canada-France- Hawaii Telescope, Gemini Northern Telescope, University of Hawaii 2.2-metre Telescope, United Kingdom Infrared Telescope and University of Hawaii 0. 6-metre Telescope. The 10- metre CSO telescope carries out submillimetre astronomy, mainly to study the properties of gas and dust in regions of star formation. Radiation at submillimetre wavelength is absorbed by water in the Earth's atmosphere and so such telescopes must be at high altitudes. CSO is on the dormant 4200-metre-high volcano Mauna Kea in Hawaii, USA.