Combined Array for Research in Millimeter-wave Astronomy
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Owens Valley Radio Observatory  , United States of America
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| Coordinates | 37°16′49″N 118°08′31″W / 37.2804°N 118.142°WCoordinates: 37°16′49″N 118°08′31″W / 37.2804°N 118.142°W |
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California Institute of Technology
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| Altitude | 2,196.223 m (7,205.46 ft) |
| Website | www |
 Location of Combined Array for Research in Millimeter-wave Astronomy
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The Combined Array for Research in Millimeter-wave Astronomy (CARMA) was an astronomical instrument comprising 23 radio telescopes. These telescopes formed an astronomical interferometer where all the signals are combined in a purpose-built computer (a correlator) to produce high-resolution astronomical images. The telescopes ceased operation in April 2015 and were relocated to the Owens Valley Radio Observatory for storage.
According to the CARMA observatory catalog, the median height of all telescope pads was at an elevation of 2196.223 m (7205.807 ft). The observatory was located in the Inyo Mountains to the east of the Owens Valley Radio Observatory, at a site called Cedar Flat, accessed through Westgard Pass. The high elevation site was chosen to minimize millimeter wave absorption and phase decoherence by atmospheric water vapor.
Until the Atacama Large Millimeter Array in Chile is in full operation, this instrument was the most powerful millimeter wave interferometer in the world.
This array was unique for being a heterogeneous collection of radio telescopes of varying sizes and design. There were three types of telescopes, all Cassegrain reflector antennas with parabolic primary mirrors and hyperbolic secondary mirrors:
As of November 2006[update], the 6 telescopes from the OVRO array and the 9 telescopes from the BIMA array are working together to gather scientific data. Pioneering work on compensating for the image distortion resulting from turbulent water vapor distributions in the troposphere started in the fall of 2008.
The most extended configurations of the array required for viewing the finest details in astronomical images, the telescopes are separated by up to 2 km. Over these distances the variation in the time of arrival of signals at the different telescopes as they pass through different amounts of water vapor severely limits the quality of images.
By siting an SZA antenna near each of the CARMA antennas and observing a compact astronomical radio source near the source under study, the properties of the atmosphere can be measured on time scales as short as a couple of seconds. This information can be used in the data reduction process to remove a significant fraction of the degradation caused by the atmospheric scintillation.
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