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Combined Array for Research in Millimeter-wave Astronomy
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 (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.
The Atacama Large Millimeter Array in Chile has succeeded CARMA as the most powerful millimeter wave interferometer in the world.[citation needed]
According to the CARMA observatory catalog, the median height of all telescope pads was at an elevation of 2,196.223 meters (7,205.456 ft). The observatory was located in the Inyo Mountains to the east of the Owens Valley Radio Observatory, at a site called Cedar Flat (after relocating the Cedar Flat Group Camps to the west of Hwy-168), accessed through Westgard Pass. The high elevation site was chosen to minimize millimeter wave absorption and phase decoherence by atmospheric water vapor.
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:
According to Leo Blitz, when in 1996 he took over directorship of Berkeley's Radio Astronomy Laboratory, the giant millimeter-wave astronomy project now in Atacama (ALMA) was already in prospect, although far from completion. Over the next decade-plus, RAL moved the millimeter-wave telescopes that had been at their Hat Creek site -- six from OVRO and nine from BIMA -- to the higher-altitude at Cedar Flat, and coordinated them in what became known as CARMA. (They were replaced at Hat Creek by the beginnings of the Allen Telescope Array.)
As of November 2006[update], the first fifteen telescopes were 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, up to 2 kilometers (1.2 mi), were required for viewing the finest details in astronomical images.[citation needed] 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 could be measured on time scales as short as a couple of seconds. This information could be used in the data reduction process to remove a significant fraction of the degradation caused by the atmospheric scintillation.
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Combined Array for Research in Millimeter-wave Astronomy
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 (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.
The Atacama Large Millimeter Array in Chile has succeeded CARMA as the most powerful millimeter wave interferometer in the world.[citation needed]
According to the CARMA observatory catalog, the median height of all telescope pads was at an elevation of 2,196.223 meters (7,205.456 ft). The observatory was located in the Inyo Mountains to the east of the Owens Valley Radio Observatory, at a site called Cedar Flat (after relocating the Cedar Flat Group Camps to the west of Hwy-168), accessed through Westgard Pass. The high elevation site was chosen to minimize millimeter wave absorption and phase decoherence by atmospheric water vapor.
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:
According to Leo Blitz, when in 1996 he took over directorship of Berkeley's Radio Astronomy Laboratory, the giant millimeter-wave astronomy project now in Atacama (ALMA) was already in prospect, although far from completion. Over the next decade-plus, RAL moved the millimeter-wave telescopes that had been at their Hat Creek site -- six from OVRO and nine from BIMA -- to the higher-altitude at Cedar Flat, and coordinated them in what became known as CARMA. (They were replaced at Hat Creek by the beginnings of the Allen Telescope Array.)
As of November 2006[update], the first fifteen telescopes were 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, up to 2 kilometers (1.2 mi), were required for viewing the finest details in astronomical images.[citation needed] 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 could be measured on time scales as short as a couple of seconds. This information could be used in the data reduction process to remove a significant fraction of the degradation caused by the atmospheric scintillation.