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

The CSO receives natural radiation emitted by celestial objects at short millimeter and submillimeter wavelengths. This spectral range is particularly important for the study of interstellar molecules. The CSO never transmits signals.

Astronomers use the CSO to observe objects in our Solar System, in our Galaxy, and in galaxies across the Universe. They study the chemistry of interstellar gas, the conditions surrounding star birth, the late stages of stellar evolution, and the history of star formation across cosmic time. It has taken about 12 billion years for light to reach us from the most distant galaxy observed with the CSO.

Because atmospheric water vapor interferes with submillimeter observations, the CSO is located high on Mauna Kea to take advantage of the very dry conditions. Most observations are made at night when the atmosphere is driest and most stable.

Prof. Robert B. Leighton designed and built the CSO at Caltech. The eighty four hexagonal panels of the primary mirror are made of lightweight aluminum honeycomb. An active system maintains the panel alignment to provide the smooth surface needed for submillimeter observations. The CSO's first observations occurred in 1986.

The CSO is equipped with advanced spectrometers and cameras. For maximum sensitivity, the detectors in these instruments are cooled with liquid helium close to absolute zero temperature. The instruments are developed at Caltech and other universities with substantial involvement by graduate students and young scholars.

In addition to Caltech, JPL, and University of Hawai'i scientists, astronomers from all over the world use the CSO. Much of the observing time has been allocated to astronomers from the general US and international community on the basis of competitive proposals.

The California Institute of Technology (Caltech) operates the CSO. Until 2013 March, the National Science Foundation provided support. The CSO is located on Mauna Kea through an agreement with the University of Hawai'i. Prof. Sunil Golwala is the director of the CSO.

Further information about History of the CSO.