月球交会对接VLBI差分时延研究

中国探月3期任务中,月球交会对接技术是任务成功的重要保障.利用嫦娥3号(CE03)绕月飞行的VLBI (Very Long Baseline Interferometry)时延数据,模拟仿真绕月交会对接过程中,同波束VLBI观测模式下,差分群时延的变化情况.仿真结果显示,在远程导引段,轨道器和上升组合体轨道距离保持100 km,持续半小时,差分群时延很好地反映了两者的轨道信息,可以用于定轨定位;自主控制段,上升组合体靠近轨道器,在轨道距离从5 km减小到20 m过程中,上升组合体加速追赶轨道器时,差分群时延快速趋近于0,上升组合体减速远离轨道器时,差分群时延绝对值快速变大.最后,利用嫦娥3号奔月段同时发射两个DOR (Differential One-Ranging)信号的VLBI时延数据,计算差分相时延,初步展示了月球交会对接过程中同波束VLBI差分相时延的误差情况.

Study on VLBI Differential Delay of Lunar Rendezvous and Docking

The lunar rendezvous and docking technology is an important guarantee for our third phase of lunar exploration. In this paper, by using the VLBI (Very Long Baseline Interferometry) delay of CE03 (Changé-03) which was around the moon, the changing of differential group delay (DGD) under the SBI (same-beam VLBI) observation mode was simulated. The simulation results indicated that the orbit distance between orbiter and ascender was kept in 100 kilometers and it lasted for half an hour. The track information of these two were well reflected by DGD which can be used for orbit determination. In the approach stage, DGD is rapidly approaching to 0, as the ascender accelerated and closed to the orbiter, while the orbit distance was reduced from 5km to 20m, and was rapidly increased as the ascender was far away from orbiter. At last, using the VLBI delay of CE03 which was halfway to the moon and transmitted two DOR (Differential One-Ranging) signals that were observed by CVN (Chinese VLBI Network), we calculated DPD (Differential Phase Delay) and preliminarily showed the error of DPD.