VLBI相位连接以及相时延解算的新方法研究

A New Try of Connecting Phase and Resolving Phase Delay in VLBI

甚长基线干涉测量(VLBI,Very Long Baseline Interferometry)能够提高深空探测器测定轨的精度,目前应用于深空探测中的多为差分VLBI技术(?VLBI).差分VLBI相关相位中存在时间间隔,把不同时间段的相位无整周模糊度地连接起来能清晰地反映卫星运动轨迹,有助于提高卫星的测定轨精度和开展行星无线电科学研究.同时,VLBI相时延因其超高的精度有广泛应用,但解算条件苛刻.基于此,首先利用两个频点的差分相位与单频点相位变化趋势一致的思想,研究了一种新方法连接差分VLBI单频点的相位;然后提出一种利用窄带宽(1 MHz)中的两个频点相位解算相时延的方法,并用嫦娥三号(CE3)着陆器的数据做了实际解算和验证;最后给出了仅利用数天VLBI相时延对着陆器进行定位的方法,得到的结果为(44.1239°N,19.5106°W),和事后基于美国月球侦察轨道器(LRO)窄角相机(NAC)影像数据的定位结果(44.12189°N,19.51129°W)相比,差异为百米左右,验证了仅利用VLBI相时延也能进行着陆器定位的有效性.

In the deep space exploration, the differential very long baseline inter- ferometry （AVLBI） technique is often used. It can help to achieve better orbit and position determinations of spacecraft. But in the AVLBI observation, the correlation phases have gaps in time domain. Connecting the correlation phases without ambiguity 2π helps to resolve the phase delay and obtain spacecraft＇s orbit with a higher accuracy, and also can make contributions to the planetary science study. Meanwhile, the phase delay is a promising measurement in many fields because of its extremely high accuracy, but it＇s hard to be obtained. Thus we studied the correlation phase connection and phase delay resolution using the Chang＇E-3 data. For the phase connection, we first implemented the idea that differential phase was changing in the same trend with a single spectral line＇s phase, and then we adjusted the phase ambiguities according to phase closure results. For the phase delay resolution, the method is using phases of two spectral lines which are spaced in a narrow band （1 MHz） to resolve the phase ambiguities. We calculated the phase delay of Chang＇E-3 lander, and by only utilizing the VLBI phase delay results, we obtained the lander＇s location as 44.1239°N, 19.5106°W. The reference of the lander＇s location is 44.12189°N, 19.51129°W with an accuracy of 20 m. The difference between the two results is about one hundred meters, which proves that the VLBI phase delay can be used Mone to determine the spacecraft＇s position.