ALMA Memo No . 496 183 GHz water vapour radiometers for ALMA : Estimation of phase errors under varying atmospheric conditions
ALMA Memo No . 496 183 GHz water vapour radiometers for ALMA : Estimation of phase errors under varying atmospheric conditions
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发表时间：
2004
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通讯作者：
J. Pardo
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作者：
A. Stirling;R. Hills;J. Richer;J. Pardo
我们研究了水蒸气辐射计作为估计大气水引起的相位的工具的使用，重点是不同的大气条件对路径长度和亮温之间关系的影响。我们提供了在各种大气条件下两者之间的转换公式，并概述了如何结合辐射计通道温度来给出路径差的最佳估计。这一估计由于大气变化，每毫米可降水水蒸气的误差约为2%。我们还考虑了水流星的存在，如冰或水滴，我们表明，具有边带分离的辐射计可以用来检测尺寸为75μm的晶体中0.02 mm的柱状积分冰的存在，以及大约10−3 mm水滴的存在。
We investigate the use of water vapour radiometers as a tool for estimating phase due to atmospheric water, focusing on the impact of differing atmospheric conditions on the relationship between path length and brightness temperature. We provide a formula for converting between the two for a variety of atmospheric conditions, and outline how the radiometer channel temperatures may be combined to give an optimal estimate for the path difference. This estimate gives an error of about 2% per mm of precipitable water vapour due to atmospheric variations. The presence of hydrometeors such as ice or water droplets is also considered, and we show that radiometers possessing sideband separation could be used to detect the presence of 0.02 mm of column integrated ice for crystals of size 75μm, and about 10−3 mm of water droplets.