In situ measurement of MWA primary beam variation using ORBCOMM
In situ measurement of MWA primary beam variation using ORBCOMM
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DOI：
10.1017/pasa.2018.30
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发表时间：
2018-08
影响因子：
6.3
通讯作者：
J. Line;B. McKinley;J. Rasti;M. Bhardwaj;R. Wayth;R. Webster;D. Ung;D. Emrich;L. Horsley;A. Beardsley;B. Crosse;T. Franzen;B. Gaensler;M. Johnston-Hollitt;D. Kaplan;D. Kenney;M. Morales;D. Pallot;K. Steele;S. Tingay;C. Trott;M. Walker;A. Williams;C. Wu
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作者：
J. Line;B. McKinley;J. Rasti;M. Bhardwaj;R. Wayth;R. Webster;D. Ung;D. Emrich;L. Horsley;A. Beardsley;B. Crosse;T. Franzen;B. Gaensler;M. Johnston-Hollitt;D. Kaplan;D. Kenney;M. Morales;D. Pallot;K. Steele;S. Tingay;C. Trott;M. Walker;A. Williams;C. Wu
摘要我们提供了Murchison宽场阵列天线单元波束形状的第一次现场测量。大多数当前的处理流水线使用假定的光束形状，这可能导致绝对和相对通量密度误差和偏振“泄漏”。因此，了解初级束至关重要，特别是对于敏感实验，例如测量再电离时期的21厘米线，其中校准要求非常极端，以至于光束之间的变化可能会影响我们进行检测的能力。测量来自vibrant的初级束流形状是具有挑战性的，因为多种仪器，大气和天体物理因素导致数据的不确定性。基于Neben等人[Radio Sci.，50，614]，我们在信号的任何数字化或相关之前直接接入望远镜的接收元件。使用ORBCOMM卫星通行证，我们能够为XX偏振中的四个单独的瓦片制作全天空地图。我们发现与Sokolowski等人的波束模型非常一致。[2017，PASA，34，e062]，并在我们的一个波束图中清楚地观察到瓦片丢失偶极子的影响。最后，我们激励和概述额外的现场实验。
Abstract We provide the first in situ measurements of antenna element beam shapes of the Murchison Widefield Array. Most current processing pipelines use an assumed beam shape, which can cause absolute and relative flux density errors and polarisation ‘leakage’. Understanding the primary beam is then of paramount importance, especially for sensitive experiments such as a measurement of the 21-cm line from the epoch of reionisation, where the calibration requirements are so extreme that tile to tile beam variations may affect our ability to make a detection. Measuring the primary beam shape from visibilities is challenging, as multiple instrumental, atmospheric, and astrophysical factors contribute to uncertainties in the data. Building on the methods of Neben et al. [Radio Sci., 50, 614], we tap directly into the receiving elements of the telescope before any digitisation or correlation of the signal. Using ORBCOMM satellite passes we are able to produce all-sky maps for four separate tiles in the XX polarisation. We find good agreement with the beam model of Sokolowski et al. [2017, PASA, 34, e062], and clearly observe the effects of a missing dipole from a tile in one of our beam maps. We end by motivating and outlining additional on-site experiments.