文章基本信息

标题：Direction-dependent Corrections in Polarimetric Radio Imaging. II. A-solver Methodology: A Low-order Solver for the A-term of the A-projection Algorithm
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作者：P. Jagannathan ; S. Bhatnagar ; W. Brisken 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2018
卷号：155
期号：1
页码：1-11
DOI：10.3847/1538-3881/aa989f
语种：English
出版社：American Institute of Physics
摘要：The effects of the antenna far-field power pattern limits the imaging performance of modern wide-bandwidth, highsensitivity interferometric radio telescopes. Given a model for the aperture illumination pattern (AIP) of the antenna, referred to as the A-term, the wide-band (WB) A-Projection algorithm corrects for the effects of its time, frequency, and polarization structure. The level to which this correction is possible depends on how accurately the A-term represents the true AIP. In this paper, we describe the A-Solver methodology that combines physical modeling with optimization to holographic measurements to build an accurate model for the AIP. Using a parametrized ray-tracing code as the predictor, we solve for the frequency dependence of the antenna optics and show that the resulting low-order model for the Karl G. Jansky Very Large Array antenna captures the dominant frequency-dependent terms. The A-Solver methodology described here is generic and can be adapted for other types of antennas as well. The parameterization is based on the physical characteristics of the antenna structure and optics and is therefore arguably a compact representation (minimized degrees of freedom) of the frequencydependent structure of the antenna A-term. In this paper, we also show that the parameters derived from A-Solver methodology are expected to improve sensitivity and imaging performance out to the first side-lobe of the antenna.
关键词：methods: numerical;polarization;radio continuum: general;techniques: image processing;techniques: interferometric