MeerKAT在UHF、L和S波段的全息测量
MeerKAT Holography Measurements in the UHF, L, and S bands
摘要：
介绍了使用MeerKAT望远镜对其支持的每个观测波段，即UHF（544- 1087 MHz）、L（856- 1711 MHz）和S（1750- 3499 MHz）进行的无线电全息测量。由于UHF波段接收机设计是L波段接收机设计的缩放版本，因此这两个波段中的电磁性能彼此非常相似。尽管也是线性极化的，S波段接收器具有与较低的两个波段完全不同的设计和明显的性能特征。正如在以前的工作中介绍的L波段，高阶波导模式激活的证据也出现在S波段的测量，但有其表现形式的差异。频率相关的指向（波束斜视），波束宽度，波束椭圆率，误差波束，仪器偏振和交叉偏振功率测量说明了MeerKAT的每个观测波段在并排的风格，以方便比较的功能。还讨论了在这些相对较低的观测频率下测量的准直误差和主反射面误差的推导。结果包括海拔和环境温度对准直的影响，以及准直随时间推移而退化的特征。随附的数据发布包括所有频段和天线的完整琼斯矩阵主波束模式的快照，以及相应的导出度量。
英文摘要：
Radio holographic measurements using the MeerKAT telescope are presented for each of its supported observing bands, namely UHF (544--1087 MHz), L (856--1711 MHz) and S (1750--3499 MHz). Because the UHF-band receiver design is a scaled version of that of the L band, the electromagnetic performance in these two bands are expectedly similar to one another. Despite also being linearly polarized, S-band receivers have an entirely different design and distinct performance characteristics from the lower two bands. As introduced in previous work for the L band, evidence of higher-order waveguide mode activation also appears in S-band measurements but there are differences in its manifestation. Frequency-dependent pointing (beam squint), beam width, beam ellipticity, errorbeam, instrumental polarization and cross-polarization power measurements are illustrated for each of MeerKAT's observational bands in a side-by-side style to facilitate the comparison of features. The derivation of collimation errors and main reflector surface errors from measurements made at these relatively low observation frequencies is also discussed. Results include elevation and ambient temperature effects on collimation, as well as the signatures of collimation degrading over time. The accompanying data release includes a snapshot of full Jones matrix primary beam patterns for all bands and antennas, with corresponding derived metrics.
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