通过射电全息术对艾伦望远镜阵列的主波束与碟面进行表征
摘要
艾伦望远镜阵列 (ATA) 是位于加州的厘米波干涉仪，由 42 个直径为 6 米的天线单元组成。我们利用双天线干涉测量法和射电全息术表征了天线的光学精度。各望远镜相对于平均值的畸变很小，均方根 (RMS) 差异仅为波束峰值的 1%。全息术提供了碟面照明方向的图像，从而能够对建成后的镜面表面进行表征。由于安装应力或太阳辐射，ATA 碟面在长达 2 米的尺度上可能会出现毫米级的畸变。实验测得的 RMS 误差在夜间为 0.7 mm，在最恶劣的太阳照射条件下为 3 mm。对于 4、10 和 15 GHz 的频率，夜间数值分别表明灵敏度损失为 1%、10% 和 20%。ATA 卓越的宽带宽允许在 0.5 至 11.2 GHz 的连续范围内进行观测，未来的改造可能会将此范围扩大至 15 GHz。波束方向图显示出随焦点缓慢变化的频率依赖性。我们探测了天线光学增益和波束方向图稳定性随焦点和观测频率的变化，得出结论：ATA 能够在跨越十倍频程的同时观测频率下生成高保真图像。在白天，天线的灵敏度和指向精度会受到影响。我们发现，在高于 5 GHz 的频率下，白天观测将遭受一定的灵敏度损失，因此可能有必要每 1 至 2 小时进行一次天线指向修正。
引用
@article{arxiv.1210.8246,
title = {Primary Beam and Dish Surface Characterization at the Allen Telescope Array by Radio Holography},
author = {ATA GROUP and Shannon Atkinson and D. C. Backer and P. R. Backus and William Barott and Amber Bauermeister and Leo Blitz and D. C. -J. Bock and Geoffrey C. Bower and Tucker Bradford and Calvin Cheng and Steve Croft and Matt Dexter and John Dreher and Greg Engargiola and Ed Fields and Carl Heiles and Tamara Helfer and Jane Jordan and Susan Jorgensen and Tom Kilsdonk and Colby Gutierrez-Kraybill and Garrett Keating and Casey Law and John Lugten and D. H. E. MacMahon and Peter McMahon and Oren Milgrome and Andrew Siemion and Ken Smolek and Douglas Thornton and Tom Pierson and Karen Randall and John Ross and Seth Shostak and J. C. Tarter and Lynn Urry and Dan Werthimer and Peter K. G. Williams and David Whysong and G. R. Harp and R. F. Ackermann and Z. J. Nadler and Samantha K. Blair and M. M. Davis and M. C. H. Wright and J. R. Forster and D. R. DeBoer and W. J. Welch},
journal= {arXiv preprint arXiv:1210.8246},
year = {2018}
}
备注
19 pages, 23 figures, 3 tables, Authors indicated by an double dagger ({\ddag}) are affiliated with the SETI Institute, Mountain View, CA 95070. Authors indicated by a section break ({\S}) are affiliated with the Hat Creek Radio Observatory and/or the Radio Astronomy Laboratory, both affiliated with the University of California Berkeley, Berkeley CA