论文标题
L频带中的Meerkat主束测量
MeerKAT Primary Beam Measurements in the L Band
论文作者
论文摘要
Meerkat天线的全极光束图案已通过使用天体靶标的无线电全息图在L波段（856至1711 MHz）中测量。本文介绍了这些梁的观察到的频率依赖性特性，并指导了该64个天线射电望远镜的用户，这些望远镜的方向依赖性极化效应涉及。在这项工作中，由于简化建模，平均带宽，重力负载和环境温度在梁的半功率区域内进行了量化。就典型用例效应的重要性水平提供了观点。结果表明，天线指向是望远镜用户的不准确性的主要原因，这是由于望远镜指向精度的$σ\ \ = 0.6 $ arcminutes的望远镜指向准确性，因此在梁的一半功率点附近引入了超过1％的功率的误差。忽略这些指向错误，相对于阵列平均值，Stokes I梁形状的可变性最常大约为0.3％的功率；但是，高于1500 MHz的影响平均是频段下半部分的三倍。之所以发生这种情况，是因为激活和传播的高阶波导模式的比例对每个接收器的矫形器传感器的较小制造差异敏感。包括轴频谱指数测量实验的一级梁校正验证测试结果。
Full-polarization primary beam patterns of MeerKAT antennas have been measured in L-band (856 to 1711 MHz) by means of radio holography using celestial targets. This paper presents the observed frequency dependent properties of these beams, and guides users of this 64 antenna radio telescope that are concerned by its direction dependent polarization effects. In this work the effects on the primary beams due to modeling simplifications, bandwidth averaging, gravitational loading and ambient temperature are quantified within the half power region of the beam. A perspective is provided on the level of significance of typical use case effects. It is shown that antenna pointing is a leading cause of inaccuracy for telescope users in the presumed beam shape, introducing errors exceeding 1% in power near the half power point of beams, owing to a telescope pointing accuracy of $σ\approx 0.6$ arcminutes. Disregarding these pointing errors, variability in the Stokes I beam shape relative to the array average is most commonly around 0.3% in power; however, the impact above 1500 MHz is on average triple that of the lower half of the band. This happens because the proportion of higher order waveguide modes that are activated and propagate is sensitive to small manufacturing differences in the orthomode transducer for each receiver. Primary beam correction verification test results for an off-axis spectral index measurement experiment are included.
