基于卫星DOR信号的VLBI相时延解算方法研究

Method of Calculating VLBI Phase Delay Based on DOR Signal of a Satellite

VLBI技术是深空探测中主要的测角手段,其对与视线垂直方向上卫星的轨道和位置变化有很高的灵敏度。基于DOR信号的VLBI观测量一般是群时延,其精度一般为纳秒量级,在约2000km的基线长度上,月球探测器的位置测量误差达近百米,对深空探测器来说位置测量误差会更大。为了提高卫星测定轨测定位精度,研究了含微小偏倚量的VLBI相时延的解算算法,并利用嫦娥二号△DOR观测数据对连续观测和间断观测时的算法进行了验证。结果表明:两种观测模式下皆可行。经过比较,相时延的随机误差大幅降低。

In deep space exploration, the VLBI technique is a precise method for the angular measurement, which can give the plane-of-sky position information. The group delay of DOR signal can usually be obtained with an accuracy of nanosecond in the VLBI observation. The accuracy of group delay can bring an orbital error of lunar probe about a hundred meters for a baseline of about 2000 kilometers. Especially in the further deep space exploration, the orbital error will be much larger. A method to calculate the small biased phase delay of VLBI is proposed in this paper in order to improve the accuracy of the orbit and position determination. The small biased phase delay is acquired by using the phase delay with ambiguity approaching the middle of bandwidth synthesis group delay of DOR signal. The method both in continuous and discontinuous observation is feasible, proved by processing the data from CE-2 satellite A DOR experiments. The relationship between the group delay and phase delay is discussed. Both of the closure group delay and the closure phase delay of three baselines of SH-BJ, SH-UR and BJ-UR are calculated, and the errors of them are analyzed. The phases of the carrier and the DOR tones are compared to prove the validity of the method. The phase delay＇s error, especially the random error, can be reduced. The system error wilt be acquired hopefully during the further processing of orbital determination.