The Caltech Submillimeter Observatory (CSO) is one of the world's premier facilities for astronomical research and instrumentation development.

With the CSO, astronomers from all over the world observe light naturally emitted by celestial objects at submillimeter wavelengths. This spectral range, between infrared and radio, is particularly suited to studying the molecular gases and small solid dust particles that fill the densest regions of the interstellar medium, where stars form as gas clouds contract and collapse under the pull of gravity. Star formation is best studied in the submillimeter and infrared because interstellar dust absorbs light at shorter wavelengths. Near the end of their lives, certain stars eject copious amounts of material, forming circumstellar envelopes with a rich assortment of molecules. Submillimeter observations of galaxies outside the Milky Way trace the history of star formation during the evolution of the universe. Light from the most distant galaxy observed with the CSO was emitted 12 billion years ago.

The telescope was designed by Prof. Robert B. Leighton and built at Caltech by Leighton and Prof. Thomas G. Phillips, the founding CSO director. The CSO was installed on Maunakea in 1985-7. Eighty four lightweight hexagonal aluminum honeycomb panels make up the primary mirror. An active system aligns these panels to maintain the smooth surface needed for submillimeter observations. Spectrometers and cameras at the CSO use detectors developed at Caltech and other universities. For maximum sensitivity, these detectors are cooled close to absolute zero temperature. New instruments are deployed as detector technology advances. Because atmospheric water vapor absorbs submillimeter radiation, the CSO is located high on Maunakea to take advantage of the very dry conditions. Most observations are made at night when the atmosphere is driest and most stable. As a university facility, the CSO has a strong educational tradition: over 100 students from 25 institutions have used the CSO for doctoral research projects.

The California Institute of Technology (Caltech) operates the CSO. The CSO is located on Maunakea through an agreement with the University of Hawai'i. The National Science Foundation supported the CSO until 2013 March. Prof. Sunil Golwala is the director of the CSO.

Further information about the History of the CSO.


Observing wavelengths: 2mm — 350 μm
Primary mirror diameter: 10.4 m (34 feet)
Surface accuracy: < 15 μm r.m.s.
Pointing accuracy: 3 arcsec r.m.s.
Highest angular resolution: 8 arcseconds
Location: Maunakea, Hawai'i,
at 4070 m (13360 ft) altitude