基于光学辅助指向测量的太赫兹望远镜指向误差模型研究

针对太赫兹波段天文点源目标较少, 指向测量相对困难的特点, 研究了利用与太赫兹天线共轴的小型光学望远镜来辅助太赫兹望远镜指向测量以及建立指向误差修正模型的方法. 依托紫金山天文台1.2 m斜轴式太赫兹天线开展了光学辅助指向测量的实验研究, 利用一台安装在天线背架上的100mm口径折射式光学望远镜获得了优于2$''$的指向测量精度. 此外, 通过对斜轴天线的结构分析以及大气折射和本地恒星时(Local Sidereal Time, LST)偏差等误差来源的分析, 建立了包含23个误差项的斜轴式光学指向修正模型, 实现了约3$''$的拟合精度. 最后, 借助高精度数字摄影测量对光电轴一致性进行了标定, 并针对其对指向模型精度的影响进行了讨论. 研究成果将为南极5 m太赫兹望远镜(The 5m Dome A Terahertz Explorer, DATE5)及其他太赫兹望远镜提供指向测量和指向修正模型方面的技术参考.

Study on the Pointing Error Model of Terahertz Telescopes with Optically Assisted Pointing Measurements

In view of the scarcity of terahertz astronomical point source targets, this paper studies the method of using a small optical telescope coaxial with terahertz antenna to assist the pointing measurement of terahertz telescope and establish the pointing error correction model. Based on the 1.2m oblique axis terahertz antenna of Purple Mountain Observatory, the experiment of optical aided pointing measurement is carried out. A 100mm aperture refractive optical telescope mounted on the antenna back frame is used to obtain the pointing measurement accuracy better than 2$''$. In addition, by analyzing the structure of the slant axis antenna and the error sources of atmospheric refraction and local star time deviation, a slant axis optical pointing correction model with 23 error terms is established, and the fitting accuracy of about 3$''$ is achieved. Finally, with the help of high-precision digital photogrammetry, the photoelectric axis consistency is calibrated, and its influence on the pointing model accuracy is discussed. The research results of this paper will provide technical reference for the 5 m Dome A Terahertz Explorer (DATE5) and other terahertz telescopes in pointing measurement and correction.