Caltech Submillimeter Observatory

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Caltech Submillimeter Observatory
Caltech-CSO-telescope (fix).jpg
CSO Logo.png
Location(s) Hawaii County, Hawaii
Coordinates 19°49′21″N155°28′34″W / 19.8225°N 155.476°W / 19.8225; -155.476 Coordinates: 19°49′21″N155°28′34″W / 19.8225°N 155.476°W / 19.8225; -155.476 OOjs UI icon edit-ltr-progressive.svg
Organization California Institute of Technology   OOjs UI icon edit-ltr-progressive.svg
Altitude13,570 ft (4,140 m) OOjs UI icon edit-ltr-progressive.svg
Wavelength 1,300, 350, 850 μm (230, 860, 350 GHz)
Built–1985 (–1985) OOjs UI icon edit-ltr-progressive.svg
First light 1986  OOjs UI icon edit-ltr-progressive.svg
Decommissioned2015  OOjs UI icon edit-ltr-progressive.svg
Telescope style radio telescope   OOjs UI icon edit-ltr-progressive.svg
Diameter10.4 m (34 ft 1 in) OOjs UI icon edit-ltr-progressive.svg
Website OOjs UI icon edit-ltr-progressive.svg
USA Hawaii relief location map.svg
Red pog.svg
Location of Caltech Submillimeter Observatory
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The Caltech Submillimeter Observatory (CSO) was a 10.4-meter (34 ft) diameter submillimeter wavelength telescope situated alongside the 15-meter (49 ft) James Clerk Maxwell Telescope (JCMT) at Mauna Kea Observatories. It was engaged in submillimeter astronomy, of the terahertz radiation band. The telescope closed on September 18, 2015. As of April 2019, the telescope is set to be dismantled and its site remediated in the near future as part of the Mauna Kea Comprehensive Management Plan. [1]



In 1973 Robert Leighton proposed to the NSF to build four 10.4 meter diameter parabolic dish radio antennas. Three of these Leighton antennas were to be used as a mm-wave interferometer to be sited at 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 [2] ), 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. [3] The three antenna mm-wave interferometer at OVRO was eventually expanded to six elements, and ultimately became part of the 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. [4]

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 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.


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. CSO Horse Head.png
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 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 GHz. This wide beam system was used to map the atomic carbon line at 492 GHz over large regions of the sky. [5] The UT team also provided an 850 GHz receiver for the telescope's 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 interferometer. 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 last observation from the telescope was made on 8 September 2015, and was of Orion KL. [20]

Over 100 students from 25 institutions used the CSO for doctoral research projects. [21]


Caltech Submillimeter Observatory. Caltech-Submillimeter-Observatory (straightened).jpg
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 UKIRT, and the Hoku Keʻa telescope. [1] Two additional telescopes must also be removed by 2033, but those have not been selected as of 1 April 2019. [22]

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. [23] Delays in the environmental assessment and permitting processes have led to postponement of the telescope removal. On 24 January 2019, Robert McLaren, the interim Director of the University of Hawaii Institute of Astronomy, gave an update to state lawmakers and suggested the permitting will be accomplished in 2019 with dismantling and removal taking a year or less. [22]

See also

Related Research Articles

Mauna Kea Observatories Astronomical observatories in Hawaii

The Mauna Kea Observatories (MKO) are a number of independent astronomical research facilities and large telescope observatories that are located at the summit of Mauna Kea on the Big Island of Hawaiʻi, United States. The facilities are located in a 525-acre (212 ha) special land use zone known as the "Astronomy Precinct", which is located within the 11,228-acre (4,544 ha) Mauna Kea Science Reserve. The Astronomy Precinct was established in 1967 and is located on land protected by the Historical Preservation Act for its significance to Hawaiian culture. The presence and continued construction of telescopes is highly controversial due to Mauna Kea's centrality in native Hawaiian religion and culture, as well as for a variety of environmental reasons.

Sunyaev–Zeldovich effect

The Sunyaev–Zeldovich effect is the spectral distortion of the cosmic microwave background (CMB) through inverse Compton scattering by high-energy electrons in galaxy clusters, in which the low-energy CMB photons receive an average energy boost during collision with the high-energy cluster electrons. Observed distortions of the cosmic microwave background spectrum are used to detect the disturbance of density in the universe. Using the Sunyaev–Zeldovich effect, dense clusters of galaxies have been observed.

Asymptotic giant branch Stars powered by fusion of hydrogen and helium in shell with an inactive core of carbon and oxygen

The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars late in their lives.

James Clerk Maxwell Telescope Radio telescope in Hawaii, US

The James Clerk Maxwell Telescope (JCMT) is a submillimetre-wavelength radio telescope at Mauna Kea Observatory in Hawaii, US. The telescope is near the summit of Mauna Kea at 13,425 feet (4,092 m). Its primary mirror is 15 metres across: it is the largest single-dish telescope that operates in submillimetre wavelengths of the electromagnetic spectrum. Scientists use it to study the Solar System, interstellar dust and gas, and distant galaxies.

Arcminute Microkelvin Imager

The Arcminute Microkelvin Imager (AMI) consists of a pair of interferometric radio telescopes - the Small and Large Arrays - located at the Mullard Radio Astronomy Observatory near Cambridge. AMI was designed, built and is operated by the Cavendish Astrophysics Group. AMI was designed, primarily, for the study of galaxy clusters by observing secondary anisotropies in the cosmic microwave background (CMB) arising from the Sunyaev–Zel'dovich (SZ) effect. Both arrays are used to observe radiation with frequencies between 12 and 18 GHz, and have very similar system designs. The telescopes are used to observe both previously known galaxy clusters, in an attempt to determine, for example, their masses and temperatures, and to carry out surveys, in order to locate previously undiscovered clusters.

Submillimeter Array Astronomical radio interferometer in Hawaii, USA

The Submillimeter Array (SMA) consists of eight 6-meter (20 ft) diameter radio telescopes arranged as an interferometer for submillimeter wavelength observations. It is the first purpose-built submillimeter interferometer, constructed after successful interferometry experiments using the pre-existing 15-meter (49 ft) James Clerk Maxwell Telescope and 10.4-meter (34.1 ft) Caltech Submillimeter Observatory as an interferometer. All three of these observatories are located at Mauna Kea Observatory on Mauna Kea, Hawaii, and have been operated together as a ten element interferometer in the 230 and 345 GHz bands. The baseline lengths presently in use range from 16 to 508 meters. The radio frequencies accessible to this telescope range from 194–408 gigahertz (1.545–0.735 mm) which includes rotational transitions of dozens of molecular species as well as continuum emission from interstellar dust grains. Although the array is capable of operating both day and night, most of the observations take place at nighttime when the atmospheric phase stability is best.

Antarctic Submillimeter Telescope and Remote Observatory

Antarctic Submillimeter Telescope and Remote Observatory, or AST/RO, was a 1.7 meter diameter off-axis telescope for research in astronomy and aeronomy at wavelengths between 0.2 and 2 mm. The instrument operated between 1994 and 2005 at the South Pole with four heterodyne receivers and three acousto-optical spectrometers. It was replaced by the 10-m South Pole Telescope.

The Combined Array for Research in Millimeter-wave Astronomy (CARMA) was an astronomical instrument comprising 23 radio telescopes, dedicated in 2006. These telescopes formed an astronomical interferometer where all the signals are combined in a purpose-built computer to produce high-resolution astronomical images. The telescopes ceased operation in April 2015 and were relocated to the Owens Valley Radio Observatory for storage.

South Pole Telescope Telescope at the South Pole

The South Pole Telescope (SPT) is a 10-metre (390 in) diameter telescope located at the Amundsen–Scott South Pole Station, Antarctica. The telescope is designed for observations in the microwave, millimeter-wave, and submillimeter-wave regions of the electromagnetic spectrum, with the particular design goal of measuring the faint, diffuse emission from the cosmic microwave background (CMB). The first major survey with the SPT—designed to find distant, massive, clusters of galaxies through their interaction with the CMB, with the goal of constraining the dark energy equation of state—was completed in October 2011. In early 2012, a new camera (SPTpol) was installed on the SPT with even greater sensitivity and the capability to measure the polarization of incoming light. This camera operated from 2012–2016 and was used to make unprecedentedly deep high-resolution maps of hundreds of square degrees of the Southern sky. In 2017, the third-generation camera SPT-3G was installed on the telescope, providing nearly an order-of-magnitude increase in mapping speed over SPTpol.

Coma Cluster Cluster of galaxies in the constellation Coma Berenices

The Coma Cluster is a large cluster of galaxies that contains over 1,000 identified galaxies. Along with the Leo Cluster, it is one of the two major clusters comprising the Coma Supercluster. It is located in and takes its name from the constellation Coma Berenices.

Llano de Chajnantor Observatory Observatory

Llano de Chajnantor Observatory is the name for a group of astronomical observatories located at an altitude of over 4,800 m (15,700 ft) in the Atacama Desert of northern Chile. The site is in the Antofagasta Region approximately 50 kilometres (31 mi) east of the town of San Pedro de Atacama. The exceptionally arid climate of the area is inhospitable to humans, but creates an excellent location for millimeter, submillimeter, and mid-infrared astronomy. This is because water vapour absorbs and attenuates submillimetre radiation. Llano de Chajnantor is home to the largest and most expensive astronomical telescope project in the world, the Atacama Large Millimeter Array (ALMA). Llano de Chajnantor and the surrounding area has been designated as the Chajnantor Science Reserve by the government of Chile.

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AMiBA Radio telescope

The Yuan-Tseh Lee Array for Microwave Background Anisotropy, also known as the Array for Microwave Background Anisotropy (AMiBA), is a radio telescope designed to observe the cosmic microwave background and the Sunyaev-Zel'dovich effect in clusters of galaxies.

VY Canis Majoris Extreme oxygen-rich red hypergiant in the constellation Canis Major

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John E. Carlstrom is an American astrophysicist, and Professor, Departments of Astronomy and Astrophysics, and Physics, at the University of Chicago.

SPT-CL J0546-5345 is one of the most massive galaxy clusters ever found in the early universe. It is thought to be 7 billion light years away. It was discovered at the South Pole Telescope in 2008 by the Sunyaev-Zel'dovich-Effect. The cluster has a redshift of z=1.067. Follow-up studies using the Spitzer, Chandra and optical telescopes allowed to identify cluster members and to measure the redshift. Using the velocity dispersion, the cluster mass has been estimated to 1015 solar masses.

CFBDSIR J145829+101343

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PDS 70 T Tauri-type star in the constellation Centaurus

PDS 70 is a very young T Tauri star in the constellation Centaurus. Located approximately 370 light-years from Earth, it has a mass of 0.76 M and is approximately 5.4 million years old. The star has a protoplanetary disk containing two nascent exoplanets, named PDS 70b and PDS 70c, which have been directly imaged by the European Southern Observatory's Very Large Telescope. PDS 70b was the first confirmed protoplanet to be directly imaged.

The Leighton Radio Telescopes are 10.4 meter parabolic dish antennas designed by Robert B. Leighton in the 1970s, which were fabricated on the Caltech campus during the 1970s and 1980s. The telescope surfaces reached an accuracy of 10 microns RMS, allowing observations throughout the millimeter and submillimeter bands. In all, eight of these telescopes were made. They were used as the six elements of the Owens Valley Radio Observatory (OVRO) millimeter interferometer in California, and as single telescopes at the Caltech Submillimeter Observatory in Hawaii and the Raman Research Institute (RRI) at Bangalore, India. In the spring of 2005, the six Leighton telescopes in Owens Valley were moved to a high mountain site in the White Mountains to form the core of the CARMA array of 25 telescopes. The CARMA array was decommissioned in 2015 at which time the Leighton telescopes were moved back to OVRO, where they are now being repurposed for different projects including the CO Mapping Array Pathfinder (COMAP), the Event Horizon Telescope (EHT), and various transient detection projects.


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  21. "Overview [CSO Wiki]".
  22. 1 2 "VIDEO: Update On Taking Telescopes Off Mauna Kea". Retrieved 2019-04-02.
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