一种用于空间VLBI的射电源条纹搜索算法  

A Radio Source Fringe Search Algorithm for Space VLBI

作　　者：朱晓娜 童力[1,3,4,5] 郑为民 张娟[1,3,4,5] Zhu Xiaona;Tong Li;Zheng Weimin;Zhang Juan(Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030,China;University of Chinese Academy of Sciences,Beijing 100049,China;National Basic Public Science Data Center,Beijing 100190,China;Key Laboratory of Radio Astronomy,Chinese Academy of Sciences,Nanjing 210033,China;Shanghai Key Laboratory of Navigation and Positioning,Shanghai 200030,China)

机构地区：[1]中国科学院上海天文台,上海200030 [2]中国科学院大学,北京100049 [3]国家基础学科公共科学数据中心,北京100190 [4]中国科学院射电天文重点实验室,江苏南京210033 [5]上海市导航定位重点实验室,上海200030

出　　处：《天文研究与技术》2022年第6期568-575,共8页Astronomical Research & Technology

基　　金：国家自然科学基金(11973011);国家基础科学数据共享服务平台(DKA2017-12-02-09);中科院关键技术人才;上海市领军人才;上海天文台重点培育项目资助。

摘　　要：我国探月工程嫦娥七号将构建由中继星上4.1 m口径抛物面天线及地基射电望远镜组成的首个月地空间甚长基线干涉测量(Very Long Baseline Interferometry, VLBI)试验系统。不同于地基甚长基线干涉测量望远镜,受中继星轨道扰动和设备时延影响,射电源预报时延模型和实际时延有时可能有较大差异,导致无法引导相关处理机正常工作,需要通过射电源条纹搜索方法寻找实际时延模型才能解决这一问题。由于4.1 m空间天线口径较小,接收信号能力弱,为提高信噪比,需要长时间积分,而线性时延模型无法保证长时间的时延精度。针对这一问题,提出了一种用于空间甚长基线干涉测量的射电源条纹搜索算法,首先通过建立时延和时延率的二维搜索网格,使用每个网格点对应的先验时延和时延率构建线性时延模型;再使用该线性时延模型对原始数据分时段相关处理;然后采用二维傅里叶变换搜索残余时延和时延率,确定最大相关幅度对应的网格点;最后使用该网格点的先验时延和时延率以及残余时延和时延率重构二次项时延模型。通过对RadioAstron空间甚长基线干涉测量的地空基线实际数据处理,验证了该射电源条纹搜索算法的正确性。The fourth phase of China′s lunar exploration project will build the first lunar terrestrial Space VLBI test system composed of a 4.1 m antenna on Chang′e 7 relay satellite and a ground-based radio telescope. Different from the ground-based VLBI system, due to the influence of relay satellite orbit disturbance and equipment delay, the predicted delay model of radio source may be quite different from the actual delay, which can not guide the relevant processors VLBI-processing units to work properly. In this paper, a radio source fringe search algorithm for Space VLBI is proposed, so as to improve the weak signal receiving ability of space small aperture antenna and to satisfy the need of using quadratic delay model to ensure long-time integration accuracy. Firstly, a two-dimensional search grid about delay and delay rate is established, using the prior delay and delay rate information of each grid point, the linear delay is constructed to process the original data in different time periods. Then the residual delay and delay rate are searched by two-dimensional Fourier transform to determine the grid point corresponding to the maximum correlation amplitude value. Finally, the quadratic delay model is reconstructed by using the delay corresponding to the grid point. The algorithm can be applied to the radio source fringe search of the ground air baseline of the RadioAstron project.

关 键 词：空间VLBI 条纹搜索 时延模型 相关处理 射电源 

分 类 号：TN216[电子电信—物理电子学]