View source for Caltech Submillimeter Observatory

{{short description|Decommissioned radio telescope in Hawaii, US}}
{{Use mdy dates|date=December 2023}}
{{Infobox telescope||logo =|locmapin=USA Hawaii}}
The '''Caltech Submillimeter Observatory''' ('''CSO''') was a 10.4-meter (34&nbsp;ft) diameter submillimeter wavelength [[telescope]] situated alongside the 15-meter (49&nbsp;ft) [[James Clerk Maxwell Telescope]] (JCMT) at [[Mauna Kea Observatories]]. Beginning in 1986, it was engaged in [[submillimetre astronomy|submillimeter astronomy]] of the [[terahertz radiation]] band. The telescope closed on September 18, 2015.<ref name=":0"/>

Disassembly of the [[Caltech]] Submillimeter Observatory's (CSO) 34-foot diameter telescope on Maunakea began the week of August 28, 2023. The entire remediation process is expected to be completed by summer 2024 and cost more than $4 million. CSO is the first observatory to be removed under the Decommissioning Plan of the University of Hawaiʻi Maunakea Comprehensive Management Plan.

==History==
In 1973 [[Robert B. Leighton|Robert Leighton]] proposed to the [[National Science Foundation|NSF]] to build four 10.4 meter diameter parabolic dish radio antennas.   Three of these [[Leighton Radio Telescopes|Leighton antennas]] were to be used
as a mm-wave interferometer to be sited at [[Owens Valley Radio Observatory|OVRO]], and the fourth was to be used as a single submillimeter telescope at a high mountain site.  The proposal was approved (AST 73-04908<ref name=leighton/>), but the NSF insisted that the mm-wave array had to be completed before work on the submillimeter telescope could be started, which delayed the construction of the submillimeter telescope by almost a decade.   Mauna Kea was selected as the site for the submillimeter telescope, which became the Caltech Submillimeter Observatory, after a site survey by [[Thomas G. Phillips]].<ref name=phillips/> The three antenna mm-wave interferometer at OVRO was eventually expanded to six elements, and ultimately became part of the [[Combined Array for Research in Millimeter-wave Astronomy|CARMA]] array in California's [[Inyo Mountains]].

The CSO antenna, named the Leighton Telescope after the death of Robert Leighton in 1997, has a more precise surface than the CARMA array antennas, enabling it to make use of the superior Mauna Kea site by operating at higher frequencies.   Heating elements were also added to the stand-off pins which support the hexagonal panels, to allow active control of the surface.<ref name=Leong/>

Before being deployed to Hawaii, both the antenna (without its dish) and the dome building were assembled on the Caltech campus, at the current site of the [[Infrared Processing and Analysis Center|IPAC]] building, in order to ensure that the building and its shutter operated correctly.  Despite having assembled the building once on the Caltech campus, the construction contractor had difficulty re-assembling the building in the high altitude environment of Mauna Kea, and the contractor went bankrupt.   After the bankruptcy Caltech staff had to supervise completion of the observatory construction.

== 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/>

== Decommissioning ==
[[Image:Caltech-Submillimeter-Observatory (straightened).jpg|thumb|left|300px|Caltech Submillimeter Observatory.]]
In order to get a permit to build the [[Thirty Meter Telescope]] project on Mauna Kea, the [[University of Hawaii]] had to commit to closing and dismantling three existing observatories on the mountain. The three chosen were the CSO, the [[United Kingdom Infrared Telescope|UKIRT]], and the Hoku Keʻa telescope.<ref name=":0"/> Two additional telescopes must also be removed by 2033, but those have not been selected as of 1 April 2019.<ref name=":1"/>

On April 30, 2009, Caltech announced plans to decommission the CSO, transferring ongoing research to the next-generation [[Cerro Chajnantor Atacama Telescope]] (CCAT) in Chile. The plans called for CSO to be dismantled, beginning in 2016, with its site returned to a natural state by 2018.<ref name=decom/> [[Thirty Meter Telescope protests|Delays]] in the environmental assessment and permitting processes have led to postponement of the telescope removal.<ref name=":1"/>

[[File:CSOSiteAfterRestoration.jpg|thumb|left|The CSO site after the telescope and dome were removed, and the site was restored.]]
Disassembly of the Caltech Submillimeter Observatory's (CSO) 34-foot diameter telescope on Maunakea began the week of August 28, 2023. The entire decommissioning process was completed in July 2024 <ref name="RIP"/> and cost more than $4 million. CSO was the first observatory to be removed under the Decommissioning Plan of the University of Hawaiʻi Maunakea Comprehensive Management Plan.<ref name=underway/><ref name=paused/>

{{clear}}

==See also==
* [[Far-infrared astronomy]]
* [[List of astronomical observatories]]

==External links==
* [https://www.youtube.com/watch?v=6oFAe--jxDU Galaxy Zoo goes observing at the CSO]
* [https://www.youtube.com/watch?v=ukRyjvZbNeM& Timelapse video of the observatory's disassembly and the site restoration]
* [http://cso.caltech.edu/ Caltech Submillimeter Observatory website]

==References==
{{reflist|refs=

<ref name=paused>{{Cite web |date=December 21, 2023 |title=Telescope removed from Caltech Submillimeter Observatory atop Maunakea; decommissioning paused until spring |url=https://bigislandnow.com/2023/12/21/telescope-removed-from-caltech-submillimeter-observatory-atop-maunakea-decommissioning-paused-until-spring/ |access-date=2023-12-22 |website=Big Island Now}}</ref>

<ref name=underway>{{Cite web |date=2023-08-28 |title=Removal of Caltech Telescope from Maunakea is underway |url=https://www.hawaii.edu/news/2023/08/28/removal-of-caltech-telescope-underway/ |access-date=2023-12-22 |website=University of Hawaiʻi System News |language=en-US}}</ref>

<ref name="RIP">{{cite news |last1=Haggerty |first1=Noah |title=Caltech observatory atop Hawaii’s Mauna Kea, a source of cultural tension, is dismantled |url=https://www.latimes.com/science/story/2024-08-02/caltech-dismantles-observatory-atop-sacred-hawaiian-mountain |access-date=13 August 2024 |publisher=Los Angeles Times |date=2 August 2024}}</ref>

<ref name=":0">{{cite web|title=Third Maunakea observatory set for decommissioning|url=http://www.hawaii.edu/news/2015/10/21/third-maunakea-observatory-set-for-decommissioning/|website=University of Hawaii News|date=21 October 2015 |publisher=University of Hawaii|access-date=3 December 2015}}</ref>

<ref name=leighton>{{cite web |last1=Leighton |first1=Robert B. |title=Final Technical Report |url=https://authors.library.caltech.edu/35046/1/Leighton_Robert-AST_73-04908.pdf |website=Caltech Library |access-date=31 Oct 2020}}</ref>

<ref name=phillips>{{cite book |last1=Phillips |first1=T. G. |title=2007 IEEE/MTT-S International Microwave Symposium |chapter=The Caltech Submillimeter Observatory |date=June 2007 |pages=1849–1852 |doi=10.1109/MWSYM.2007.380111 |bibcode=2007ims..confE...1P |isbn=978-1-4244-0687-6 |s2cid=1708648 |url=https://resolver.caltech.edu/CaltechAUTHORS:20101015-110822698 |chapter-url=https://ieeexplore.ieee.org/document/4264219 |access-date=30 October 2020}}</ref>

<ref name=Leong>{{cite book |last1=Leong |first1=Melanie |last2=Peng |first2=Ruisheng |last3=Yoshida |first3=Hiroshige |last4=Chamberlin |first4=Richard |last5=Phillips |first5=Thomas G. |chapter=A Caltech Submillimeter Observatory Active Optics System |title=Submillimeter Astrophysics and Technology: A Symposium Honoring Thomas G. Phillips |date=2009 |series=ASP Conference Series |volume=417 |isbn=978-1-58381-714-8 |pages=131–135 |url=http://articles.adsabs.harvard.edu/pdf/2009ASPC..417..131L |access-date=30 October 2020}}</ref>

<ref name=Plume>{{cite journal |last1=Plume |first1=Rene |last2=Jaffe |first2=Daniel T. |title=The World's Smallest 10-meter Submillimeter Telescope |journal=Publications of the Astronomical Society of the Pacific |date=May 1995 |volume=107 |pages=488–495 |doi=10.1086/133579 |bibcode=1995PASP..107..488P |s2cid=120255254 |url=https://iopscience.iop.org/article/10.1086/133579/pdf |access-date=19 November 2020|url-access=subscription }}</ref>

<ref name=Wilbanks>{{cite journal |last1=Wilbanks |first1=T. M. |last2=Ade |first2=P. A. R. |last3=Fischer |first3=M. L. |last4=Holzapfel |first4=W. L. |last5=Lange |first5=A. E. |title=Measurement of the Sunyaev-Zel'dovich Effect toward Abell 2163 at a Wavelength of 2.2 Millimeters |journal=Astrophysical Journal Letters |date=June 1994 |volume=427 |pages=L75–L78 |doi=10.1086/187368 |bibcode=1994ApJ...427L..75W |url=http://articles.adsabs.harvard.edu/pdf/1994ApJ...427L..75W |access-date=31 October 2020}}</ref>

<ref name=Hansen>{{cite journal |last1=Hansen |first1=Steen H. |last2=Pastor |first2=Sergio |last3=Semikoz |first3=Dmitry V. |title=First Measurement of Cluster Temperature Using the Thermal Sunyaev-Zel'dovich Effect |journal=Astrophysical Journal Letters |date=July 2002 |volume=573 |issue=2 |pages=L69–L71 |doi=10.1086/342094 |arxiv=astro-ph/0205295 |bibcode=2002ApJ...573L..69H |s2cid=6540903 |url=https://iopscience.iop.org/article/10.1086/342094/pdf |access-date=31 October 2020}}</ref>

<ref name=Aguirre>{{cite journal |last1=Aguirre |first1=James E. |last2=Ginsburg |first2=Adam G. |last3=Dunham |first3=Miranda K. |last4=Drosback |first4=Meredith M. |last5=Bally |first5=John |last6=Battersby |first6=Cara |last7=Bradley |first7=Eric Todd |last8=Cyganowski |first8=Claudia |last9=Dowell |first9=Darren |last10=Evans |first10=Neal J. |last11=Glenn |first11=Jason |last12=Harvey |first12=Paul |last13=Rosolowsky |first13=Erik |last14=Stringfellow |first14=Guy S. |last15=Walawender |first15=Josh |last16=Williams |first16=Jonathan P. |title=The Bolocam Galactic Plane Survey: Survey Description and Data Reduction |journal=Astrophysical Journal Supplement Series |date=January 2011 |volume=192 |issue=1 |page=4 |doi=10.1088/0067-0049/192/1/4 |arxiv=1011.0691 |bibcode=2011ApJS..192....4A |hdl=2152/42997 |s2cid=119275808 |url=https://iopscience.iop.org/article/10.1088/0067-0049/192/1/4 |access-date=6 November 2020}}</ref>

<ref name=Menten>{{cite journal | last1=Menten |first1=K. M. |last2=Melnick |first2=G. J. |last3=Phillips |first3=T. G. |title=Submillimeter Water Masers |journal=Astrophysical Journal Letters |date=1990 |volume=350 |pages=L41–L44 |doi=10.1086/185663 |bibcode=1990ApJ...350L..41M |url=http://articles.adsabs.harvard.edu/pdf/1990ApJ...350L..41M |access-date=6 November 2020}}</ref>

<ref name=H2O>{{cite journal |last1=Menten |first1=K. M. |last2=Melnick |first2=G. J. |last3=Phillips |first3=T. G. |last4=Neufeld |first4=D. A. |title=A New Submillimeter Water Maser Transition at 325 GHz |journal=Astrophysical Journal Letters |date=1990 |volume=363 |pages=L27–L31 |doi=10.1086/185857 |bibcode=1990ApJ...363L..27M |url=http://articles.adsabs.harvard.edu/pdf/1990ApJ...363L..27M |access-date=31 October 2020}}</ref>

<ref name=M658>{{cite journal |last1=Menten |first1=K. M. |last2=Young |first2=K. |title=Discovery of Strong Vibrationally Excited Water Masers at 658 GHz Toward Evolved Stars |journal=Astrophysical Journal Letters |date=1995 |volume=450 |pages=L67–L70 |doi=10.1086/316776 |bibcode=1995ApJ...450L..67M |url=http://articles.adsabs.harvard.edu/pdf/1995ApJ...450L..67M |access-date=31 October 2020|doi-access=free }}</ref>

<ref name=M471>{{cite journal |last1=Melnick |first1=Gary J. |last2=Menten |first2=Karl M. |last3=Phillips |first3=Thomas G. |last4=Hunter |first4=Todd |title=Discovery of Interstellar Water Lines at 437, 439, and 471 GHz: Strong Case for Water Maser Formation behind C-Type Shocks |journal=Astrophysical Journal Letters |date=October 1993 |volume=416 |pages=L37–L40 |doi=10.1086/187065 |bibcode=1993ApJ...416L..37M |url=http://articles.adsabs.harvard.edu/pdf/1993ApJ...416L..37M |access-date=31 October 2020}}</ref>

<ref name=Sutton>{{cite journal |last1=Sutton |first1=E. C. |last2=Jaminet |first2=P. A. |last3=Danchi |first3=W. C. |last4=Blake |first4=Geoffrey A. |title=Molecular Line Survey of Sagittarius B2(M) from 330 to 355 GHz and Comparison with Sagittarius B2(N) |journal=Astrophysical Journal Supplement Series |date=October 1991 |volume=77 |pages=255–285 |doi=10.1086/191603 |bibcode=1991ApJS...77..255S |url=http://articles.adsabs.harvard.edu/pdf/1991ApJS...77..255S |access-date=31 October 2020}}</ref>

<ref name=Groesbeck>{{cite journal |last1=Groesbeck |first1=T. D. |last2=Phillips |first2=T. G. |last3=Blake |first3=Geoffrey A. |title=The Molecular Emission-Line Spectrum of IRC +10216 between 330 and 358 GHz |journal=Astrophysical Journal Supplement Series |year=1994 |volume=94 |issue=1 |pages=147–162 |doi=10.1086/192076 |pmid=11539132 |bibcode=1994ApJS...94..147G |url=http://articles.adsabs.harvard.edu/pdf/1994ApJS...94..147G |access-date=31 October 2020}}</ref>

<ref name=Weisstein>{{cite journal |last1=Weisstein |first1=Eric W. |last2=Serabyn |first2=E. |title=Submillimeter Line Search in Jupiter and Saturn |journal=Icarus |date=September 1996 |volume=123 |issue=1 |pages=23–36 |doi=10.1006/icar.1996.0139 |bibcode=1996Icar..123...23W |url=https://www.sciencedirect.com/science/article/abs/pii/S0019103596901396 |access-date=31 October 2020|url-access=subscription }}</ref>

<ref name=Schilke>{{cite journal |last1=Schilke |first1=P. |last2=Groesbecj |first2=T. D. |last3=Blake |first3=G. A. |last4=Phillips |first4=T. G. |title=A Line Survey of Orion KL from 325 to 360 GHz |journal=Astrophysical Journal Supplement Series |date=January 1997 |volume=108 |issue=1 |pages=301–337 |doi=10.1086/312948 |pmid=11539874 |bibcode=1997ApJS..108..301S |s2cid=5940584 |url=https://iopscience.iop.org/article/10.1086/312948/pdf |access-date=31 October 2020}}</ref>

<ref name=Schilke2>{{cite journal |last1=Schilke |first1=P. |last2=Benford |first2=D. J. |last3=Hunter |first3=T. R. |last4=Lis |first4=D. C. |last5=Phillips |first5=T. G. |title=A Line Survey of Orion-KL from 607 to 725 GHZ |journal=Astrophysical Journal Supplement Series |date=February 2001 |volume=132 |issue=2 |pages=281–364 |doi=10.1086/318951 |bibcode=2001ApJS..132..281S |s2cid=123133670 |url=https://iopscience.iop.org/article/10.1086/318951/pdf |access-date=31 October 2020|url-access=subscription }}</ref>

<ref name=crl618>{{cite journal |last1=Gammie |first1=C. F. |last2=Knapp |first2=G. R. |last3=Young |first3=K. |last4=Phillips |first4=T.G. |last5=Falgarone |first5=E. |title=A Very Fast Molecular Outflow from the Protoplanetary Nebula CRL 618 |journal=Astrophysical Journal Letters |date=1989 |volume=345 |pages=L87–L89 |doi=10.1086/185559 |bibcode=1989ApJ...345L..87G |url=http://articles.adsabs.harvard.edu/pdf/1989ApJ...345L..87G |access-date=31 October 2020}}</ref>

<ref name=eclipse>{{cite journal |last1=Ewell |first1=M. W. Jr |last2=Zirin |first2=H. |last3=Jensen |first3=J. B. |last4=Bastian |first4=T. S. |title=Submillimeter Observations of the 1991 July 11 Total Solar Eclipse |journal=Astrophysical Journal |date=January 1993 |volume=403 |pages=426–433 |doi=10.1086/172213 |bibcode=1993ApJ...403..426E |url=http://articles.adsabs.harvard.edu/pdf/1993ApJ...403..426E |access-date=31 October 2020}}</ref>

<ref name=lastobs>{{cite journal|last1=McGuire|first1=Brett A.|last2=Carroll|first2=P. Brandon|title=The Final Integrations of the Caltech Submillimeter Observatory|journal=Research Notes of the AAS|date=31 October 2017|volume=1|issue=1|page=4|doi=10.3847/2515-5172/aa9657|issn=2515-5172|arxiv=1711.09145|bibcode=2017RNAAS...1....4M|s2cid=119348746 |doi-access=free }}</ref>

<ref name=students>{{cite web |url=http://cso.caltech.edu/wiki/cso/science/overview |title = Overview [CSO Wiki]}}</ref>

<ref name=":1">{{Cite web|url=http://www.bigislandvideonews.com/2019/01/29/video-update-on-taking-telescopes-off-mauna-kea/|title=VIDEO: Update On Taking Telescopes Off Mauna Kea|website=www.bigislandvideonews.com|access-date=2019-04-02}}</ref>

<ref name=decom>{{cite press release |url=http://mr.caltech.edu/press_releases/13256 |title=Caltech Submillimeter Observatory in Hawaii to be Decommissioned |publisher=Caltech.edu |date=April 30, 2009 |access-date=December 22, 2010  |archive-url=https://web.archive.org/web/20100610094518/http://mr.caltech.edu/press_releases/13256 |archive-date=June 10, 2010 }}</ref>

<ref name="CSO-JCMT">{{cite book |last1=Carlstrom |first1=John |last2=Hills |first2=Richard |last3=Lay |first3=Oliver |last4=Force |first4=Brian |last5=Hall |first5=C. G. |last6=Phillips |first6=Thomas |last7=Schinckel |first7=Antony |title=The CSO-JCMT Submillimeter Interferometer |date=1994 |publisher=Cambridge University Press |isbn=0-937707-78-3 |pages=35-40 |edition=ASP Conference Series, Vol 59 |url=https://www.cambridge.org/core/services/aop-cambridge-core/content/view/612AA99E45FA71CD478098F993C38900/S0252921100019059a.pdf/div-class-title-the-cso-jcmt-submillimeter-interferometer-div.pdf |access-date=18 March 2024}}</ref> 

}}

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