甚长基线干涉测量(very long baseline interferometry,VLBI)技术是深空探测器测定轨的方法之一,也是行星无线电科学研究的重要手段.VLBI相时延通过解算相关相位的整周模糊度解算出探测器的VLBI时延观测量,可有效地降低相位随机误差的影响,从而提高时延测量的精度.本文论述了解算相位整周模糊度的条件和方法,给出相时延的解算方法,并分析比较了相时延与群时延的随机误差水平.以嫦娥二号(CE2)卫星飞往拉格朗日L2点的探测任务为例,求解了两个月内10次VLBI观测的相时延并分析了数据质量.相时延和群时延分别联合测速测距数据的定轨结果表明,在150万公里的距离上相时延用于探测器的定轨是可行的.
Chang'E-3 spacecraft was orbiting the Moon from December 6–14, 2013, and very long baseline interferometry(VLBI) observations were performed to improve the accuracy of its orbit determination. In the process of recording VLBI raw data, 2 bits quantization was implemented.Interesting phenomenon was that signal-to-noise ratio(SNR) of each VLBI station experienced periodical change and had large variation on amplitude while in the Moon's orbit, whereas SNR kept in a stable level after Chang'E-3 landed on the Moon. Influence of varying elevation angle on SNR was analyzed and compensation of 2 bits quantization harmonics to SNR calculation was investigated. Most importantly, telescope system noise temperature increase caused by the Moon was computed along the time of Chang'E-3 orbiting the Moon, and well matched SNR changing trend in terms of correlation coefficients.
he qingbaoliu qinghuili peijiakawaguchi noriyukiwu yajunzheng xinzhang juanxu zhijun
