Editing Caltech Submillimeter Observatory (section)

== Operation ==
[[File:CSO Horse Head.png|thumb|The [[Horsehead Nebula]], as seen in visible light on the left, and on the right as a false color image made from data taken at the CSO, of the intensity of the 230 GHz rotational transition of carbon monoxide.]]
Throughout its nearly three decade operational lifetime, the CSO was funded primarily by the NSF.
The [[University of Texas]] provided additional funding from the start of 1988 through the end of 2012.

The CSO emphasized [[heterodyne receiver]] work, while the neighboring [[James Clerk Maxwell Telescope]] emphasized continuum detector observations.   Most of the heterodyne receivers were built on the Caltech campus, and were placed at the [[Nasmyth telescope|Nasmyth focus]].   The University of Texas team built instruments for the CSO, including a re-imaging system which effectively converted the 10.4 meter telescope into a 1 meter off-axis telescope with a 3 arc minute wide beam at 492&nbsp;GHz.   This wide beam system was used to map the atomic carbon line at 492&nbsp;GHz over large regions of the sky.<ref name=Plume/>  The UT team also provided an 850&nbsp;GHz receiver for the telescope's [[Cassegrain reflector|Cassegrain focus]].

In 1986, the CSO obtained official "first light" by producing a spectrum of the [[carbon monoxide]] J=2-1 line from the nearby [[starburst galaxy]] [[Messier 82]] (although continuum detections of the Moon and some planets had been made earlier).

The CSO and JCMT were combined to form the first submillimeter [[interferometry|interferometer]].<ref name="CSO-JCMT"/> The success of this experiment was important in pushing ahead the construction of the [[Submillimeter Array]] and the [[Atacama Large Millimeter Array]] interferometers.   The CSO was also a part of the [[Event Horizon Telescope]] array during the early test observations which proved the feasibility of intercontinental mm-wave interferometry.

Research Highlights:

* The first detection of the [[Sunyaev-Zel'dovich Effect]] at millimeter wavelengths, and the first measurement of cluster temperature using the Sunyaev-Zel'dovich Effect.<ref name=Wilbanks/><ref name=Hansen/>
* The [[Bolocam Galactic Plane Survey]], a survey of continuum emission at 1.1&nbsp;mm, which covered 170 square degrees of the galactic plane.   This survey resulted in the publication of at least 14 journal papers with over 1000 aggregate citations.<ref name=Aguirre/>
* Discovery of new submillimeter water [[maser]] spectral lines at 321, 325, 437, 439, 471, and 658&nbsp;GHz.<ref name=Menten/><ref name=H2O/><ref name=M658/><ref name=M471/>
* Molecular line surveys in the submillimeter band of the star formation regions [[Sagittarius B2]] and [[Kleinmann–Low Nebula|Orion KL]]; the carbon star [[IRC+10216]]; and the planets Jupiter and Saturn.<ref name=Sutton/><ref name=Groesbeck/><ref name=Weisstein/><ref name=Schilke/><ref name=Schilke2/>
* Discovery of a ~200&nbsp;km/sec fast molecular wind from the [[protoplanetary nebula]] [[CRL 618]].   This fast neutral wind will interact with the slow [[Asymptotic Giant Branch|AGB]] wind to shape the final [[planetary nebula]].<ref name=crl618/>
* Submillimeter observations of the [[Solar eclipse of July 11, 1991]], a very unusual eclipse in that it passed over several major observatories.<ref name=eclipse/>  Observing the Sun would normally have constituted a severe violation of the telescope's sun-avoidance limits, as it was normally forbidden to allow any sunlight to fall upon even a portion of the telescope's primary mirror.  However for this special event a tent-like membrane was deployed over the dish, which prevented focused visible and infrared light from destroying the secondary mirror assembly.

The last observation from the telescope was made on 8 September 2015, and was of [[Kleinmann–Low Nebula|Orion KL]].<ref name=lastobs/>

Over 100 students from 25 institutions used the CSO for doctoral research projects.<ref name=students/>