VLSS redux: Software improvements applied to the Very Large Array Low‐Frequency Sky Survey
VLSS redux: Software improvements applied to the Very Large Array Low‐Frequency Sky Survey
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DOI：
10.1029/2011rs004941
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发表时间：
2012-05
期刊：
影响因子：
1.6
通讯作者：
W. Lane;W. Cotton;J. Helmboldt;N. Kassim
中科院分区：
文献类型：
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作者：
W. Lane;W. Cotton;J. Helmboldt;N. Kassim
我们介绍了数据处理和分析的改进细节，这些改进最近用于重新减少甚大阵列（VLA）低频巡天（VLSS）数据。所描述的算法在数据简化包Obit中实现，包括智能加窗以减少净偏置、改进的自动射频干扰去除、改进的亮源剥离以及高阶泽尼克拟合以模拟电离层相位贡献。另一个技术改进是使用原始VLSS目录作为计算电离层校正的同频/同分辨率参考，从而提高了精度和找到解决方案的数据百分比。我们还讨论了提取源目录和分析数据中存在的电离层波动的新算法。改进的减少技术导致了实质性的改进，包括六个以前未公布的领域（调查面积的1%）的图像，并减少了50%的清洁偏差。成像的最大角尺寸大约增加了一倍，编目的来源数量增加了35%，达到95，000个。
We present details of improvements to data processing and analysis which were recently used for a re‐reduction of the Very Large Array (VLA) Low‐Frequency Sky Survey (VLSS) data. Algorithms described are implemented in the data‐reduction package Obit, and include smart‐windowing to reduce clean bias, improved automatic radio frequency interference removal, improved bright‐source peeling, and higher‐order Zernike fits to model the ionospheric phase contributions. An additional, but less technical improvement was using the original VLSS catalog as a same‐frequency/same‐resolution reference for calculating ionospheric corrections, allowing more accuracy and a higher percentage of data for which solutions are found. We also discuss new algorithms for extracting a source catalog and analyzing ionospheric fluctuations present in the data. The improved reduction techniques led to substantial improvements including images of six previously unpublished fields (1% of the survey area) and reducing the clean bias by 50%. The largest angular size imaged has been roughly doubled, and the number of cataloged sources is increased by 35% to 95,000.