用于地月空间VLBI的望远镜信号合成增强技术  

Telescope signal synthesis and enhancement technology for very long baseline interferometry in Earth-Moon space

作　　者：吕钢 刘磊[1,3,4,5] 张娟 郑为民[1,3,4,5] 童力[1,3,4,5] LV Gang;LIU Lei;ZHANG Juan;ZHENG WeiMin;TONG Li(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 210023,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,南京210023 [5]上海市导航定位重点实验室,上海200030

出　　处：《中国科学：物理学、力学、天文学》2021年第9期107-116,共10页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:11973011,11573057,11803070,11903067);中国科学院空间科学预研项目(编号:XDA15016100)和中国科学院关键技术人才和上海市领军人才项目资助。

摘　　要：在我国探月工程四期中,将利用地面望远镜和月球轨道射电望远镜共同组成的超长基线,开展X频段空间VLBI试验.由于地月基线长达400000 km, UV覆盖不均匀,不适合开展常规的VLBI成图观测,相关科学研究应充分利用地月基线高角分辨率的特点并充分考虑其基线灵敏度.该试验中的空间望远镜口径仅为4.2 m,相应的中国VLBI网所属X频段射电望远镜均为25–65 m的中等口径,且地月基线长度远超过地球直径.为尽可能提高地月基线灵敏度,本文提出利用国内多面中等口径地基VLBI望远镜参与地月基线观测,通过对相关处理机输出的各条地月基线VLBI互功率谱进行综合,将各个中等口径VLBI望远镜信号进行合成,达到一个100 m级的地基大口径望远镜与月球轨道小口径望远镜进行VLBI干涉的效果.本方法基本思路为,基于软件相关处理机的输出结果,通过对齐各基线的相位,补偿基线时延,对各条地月基线的互功率谱进行相干合成,从而达到提升信噪比的目的.基于此方法,我们利用火星探测器"天问一号"实测数据进行信号合成VLBI试验.结果表明,通过进行基线的互功率谱合成,可以使基线信噪比有明显提升.此方法也可应用于未来其他有类似需求的空间VLBI数据处理.In the fourth stage of China’s Lunar Exploration Project, the Space Very Long Baseline Interferometry(SVLBI)experiment in X-band will be conducted with its ultralong baseline composed of radio telescopes on Earth and in the lunar orbit. Since the Earth-Moon baseline is 400000 km long and the low quality of UV coverage, it is unsuitable for conventional VLBI imaging. Instead, the corresponding sciences should fully utilize its high angular resolution and pay attention to its low baseline sensitivity. The aperture of the space telescope in this experiment is only 4.2 m, while the corresponding telescopes with X-band receivers in Chinese VLBI Network(CVN) are middle sized with diameters of25–65 m. Moreover, Earth-Moon baseline is much longer compared with the diameter of the earth. To improve the sensitivity of the Earth-Moon baseline, in this work, we use multiple ground based middle sized telescopes to conduct the observation. VLBI signals of each ground based telescope are synthesized, so as to achieve the performance of a large telescope with a diameter of 100 m. The basic idea is: based on the output of the correlator, the phase of each baseline is aligned, the baseline delay is compensated, and the cross power spectrum of each Earth-Moon baseline is coherently synthesized, so as to improve the signal-to-noise ratio(SNR). In the proposed method, the VLBI signal synthesis experiment is conducted using the CVN observation data. The result demonstrates that the SNR can be significantly improved by cross-power spectrum synthesis. The proposed method can also be applied to other types of space VLBI data processing with similar requirements in the future.

关 键 词：地月空间VLBI 望远镜组阵 基线合成 软件相关处理机 基线信噪比 

分 类 号：P111[天文地球—天文学] P228.6