Adaptive Calibration Of Radio Interferometer Data
Adaptive Calibration Of Radio Interferometer Data
复制标题
无线电干涉仪数据的自适应校准
DOI：
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发表时间：
1980
期刊：
影响因子：
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通讯作者：
F. Schwab
中科院分区：
文献类型：
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作者：
F. Schwab
射电干涉仪观测，本质上是V的样本，即射电亮度I在一片天空上的傅里叶变换。主要误差通常归因于阵列的各个元素。最有害的，往往是由于大气折射的相位误差，但幅度误差也可能是严重的。采样分布随着观测运行的进展而改善，因为随着地球旋转，任何一对元件都以沿着曲线的不同空间频率对V进行采样。自适应校准可以实现如下：对I的分析性质的假设导致从给定时刻开始的观测结果与总数据集的一致性的测量;给定适当的误差模型，在未知误差中的超定方程组的结果;相应地校正数据，得到I的改进估计;并且该过程可以重复。这包括Readhead和威尔金森以及Cotton提出的用于补偿甚长基线干涉测量（VLBI）中相位误差的方案; Muller和Buffington提出了用于光学望远镜的类似方法。甚大阵列（VLA）数据的分析结果是非常令人鼓舞的。计算费用是标准方法的几倍。
Radio interferometer observations are, essentially, samples of V, the Fourier transform of the radio brightness, I, on a patch of sky. The dominant errors usually are ascribable to individual elements of the array. Most damaging, often, are phase errors due to atmospheric refraction, but amplitude errors also may be serious. The sampling distribution improves as an observing run progresses since, as the earth rotates, any pair of elements samples V at different spatial frequencies lying along a curve. Adaptive calibration can be achieved as follows: Assumptions on the analytic properties of I lead to a measure of the consistency of the observations, from a given instant, with the total set of data; given an appropriate error model, an overdetermined system of equations in the unknown errors results; correcting the data accordingly, an improved estimate of I is derived; and the procedure may be repeated. This encompasses schemes proposed by Readhead and Wilkinson, and by Cotton, for compensation of phase errors in very-long-baseline interferometry (VLBI); similar methods are proposed by Muller and Buffington for optical telescopes. Results in analysis of Very Large Array (VLA) data are extremely encouraging. The computational expense is a few times that of standard methods.