22 July 2014 ALMA fast switching phase calibration on long baselines
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Abstract
We present results of feasibility studies of Atacama Large Millimeter/submillimeter Array (ALMA) interferom- eter phase calibration scheme combined with the Fast Switching (FS) phase referencing and the Water Vapor Radiometer (WVR) phase correction (FS+WVR phase correction). With FS scheme, ALMA antennas observe a scientific target source and a nearby calibrator by turn very quickly. Because interferometer phase errors of the target due to the water vapor contents commonly exist in those of the calibrator, the target phase is corrected with the calibrator phase. We have demonstrated the FS+WVR phase correction for ALMA with baselines up to 2.7 km for various switching cycle times and separations between sources. For instance, in the case of sources with the 1° separation, root-mean-square phases of the target were reduced from 300 to 40 microns in path length for 1 km baselines, and the target interferometer phases could be stabilized to an ALMA specification requirement level for the interferometer phase stability. We also analytically evaluated the root-mean-square phase corrected with the FS+WVR phase correction to predict the performance as a function of the separation and switching cycle time.
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Yoshiharu Asaki, Satoki Matsushita, Ryohei Kawabe, Ed Fomalont, Denis Barkats, Stuartt Corder, "ALMA fast switching phase calibration on long baselines", Proc. SPIE 9145, Ground-based and Airborne Telescopes V, 91454K (22 July 2014); doi: 10.1117/12.2055824; https://doi.org/10.1117/12.2055824
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