Phase Compensation Scheme for ACA Using SMA

• Main Authors: Yu-Lin Chen, 陳育霖
• Other Authors: Keh-Ning Huang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/31042235104061824317

碩士 === 國立臺灣大學 === 物理研究所 === 96 === Millimeter and submillimeter astronomers pursue science and technology development with ground-based millimeter/submillimeter interferometers through the opaque atmosphere. This waveband provides a unique window on cold dust emission and highly excited lines from molecules and ions. The next generation interferometer at this waveband is the Atacama Large Millimeter and submillimeter Array (ALMA) with the Atacama Compact Array (ACA). The interferometers at this waveband are, however, highly affected by the water vapor induced refraction, which results as phase fluctuations. To reduce the phase fluctuation, we conducted a phase correction scheme using the observing data of the Submillimeter Array (SMA) for the ACA. The phase correction schemes, interpolation and extrapolation, are studied to know how effective these scheme are. Three simultaneously detected antenna phases form a plane of a wave front, and this phase screen are used for the interpolation and extrapolation. The interpolation scheme can apparently obtain improved results, while the extrapolation scheme often does not. There are unexpectedly large phase fluctuations showed up only around the 60 meters away from the reference antennas. This can be explained with considering the frozen phase screen. It may be explained more clearly after more careful investigation of the wind aloft and the temporal and spatial turbulent structure on the summit of Mauna Kea.