用于地月空间VLBI的加权全频谱信号合成技术

A weighted full-spectrum signal combining technology for cislunar Space-VLBI

在我国探月工程四期嫦娥七号任务中,中继星将搭载一个4.2 m口径的X波段抛物面望远镜.该望远镜将与地基望远镜构成具有400000 km空地基线的月球轨道VLBI实验系统,实施地月空间VLBI实验.为尽可能提高空地VLBI基线灵敏度,提出了采用加权全频谱合成(FSC)技术增强地基信号.本文先理论推导了信号合成后的效果及两个望远镜信号合成时的最优加权系数比值.然后设计了VLBI加权全频谱合成算法,并基于实测信号利用网格搜索的方法找到最优加权系数,结果与理论推导相符.最后,利用“嫦娥四号”多组VLBI原始观测信号进行测试.结果表明,本文设计的信号合成算法可以大幅度提高VLBI基线射电源信号的信噪比.

In the Chang’E-7 mission of the fourth stage of China’s Lunar Exploration Project,the relay satellite will carry a 4.1-maperture X-band parabolic telescope.This and the ground-based telescopes will form a lunar orbit very long baseline interferometry(VLBI)experimental system with the space-ground baseline up to 400000 km.To improve the sensitivity of this baseline,we propose a weighted full-spectrum signal combining method.First,we derive the optimal weighting coefficient ratio for combining the signals of the two telescopes.Then,we propose the VLBI weighted full-spectrum combining method whose optimal weight coefficient is determined by investigating the data,and the obtained result is consistent with the theoretical derivation.Finally,we use Chang’E-4 original VLBI observation data for method testing.The results show that the signal combining method proposed in this work can greatly improve the signal-to-noise ratio for VLBI observations.