Applications of same-beam VLBI in the orbit determination of multi-spacecrafts in a lunar sample-return mission

Abstract

Same-beam VLBI means that two spacecrafts with small separation angles that transmit multi-frequency signals specially designed are observed simultaneously through the main beam of receiving antennas. In same-beam VLBI, the differential phase delay between the two spacecrafts and the two receiving antennas can be obtained within a small error of several picoseconds. As a successful application, the short-arc orbit determination of several hours for Rstar and Vstar, which are two small sub-spacecrafts of SELENE, has been much improved by using the same-beam VLBI data together with the Doppler and range data. The long-arc orbit determination of several days has also been accomplished within an error of about 10 m with the same-beam VLBI data incorporated. These results show the value of the same-beam VLBI for the orbit determination of multi-spacecrafts. This paper introduces the same-beam VLBI and Doppler observations of SELENE and the orbit determination results. In addition, this paper introduces how to use the same-beam VLBI for a lunar sample-return mission, which usually consists of an orbiter, a lander and a return unit. The paper also offers the design for the onboard radio sources in the lunar sample-return mission, and introduces applications of S-band multi-frequency same-beam VLBI in lunar gravity exploration and applications during all stages in the position/orbit determinations such as orbiting, landing, sampling, ascending, and docking.same-beam VLBI, differential phase delay, sample-return, orbit determination, lunar gravity field PACS: 95.55.Pe, 95.10.Eg, 95.55.Jz, 95.10.Jk

The application of the seam beam VLBI technique for the orbit determination of CE-5 in the rendezvous and docking phase

“…同波束VLBI测量的基本原理是利用天线的主波 束同时接收角距很小的两个或多个探测器的信号, 得 到两个或多个探测器信号的相关相位并在探测器间 进行差分, 两个探测器的时延差分即为同波束VLBI的 时延观测量. 由于两器角距离相近, 可以消除传播路 径中电离层、大气以及观测装置的绝大部分影响, 得 到的差分时延数据比传统的单探测器VLBI时延测量 精度更高 [7][8][9] . 从测量原理上, 同波束VLBI对两个探测 器的相对位置有较强的约束能力.…”

“…得到了充分应用. 在SELENE计划中, 采用S频段多频 点同波束VLBI测量技术对2个小卫星Rstar和Vstar进 行测量, 得到了精度在ps量级的差分时延数据, 联合 地基测距测速数据, 提高了2个探测器的定轨精度, 进 而提高了月球重力场的反演精度 [7] . CE-3探测器着陆 后释放了巡视器进行月面巡视, 在着陆器和巡视器之 间实现了同波束VLBI测量, 根据不同的信号源分别 提取了差分群时延和差分相时延数据, 使用ns量级的 VLBI差分群时延数据, 两器相对定位精度在百米, 使 用ps量级的VLBI差分相时延数据, 在定位过程中进行 模糊度解算, 实现了米级精度的月面相对定位 [3,4] .…”

Study on Differential Phase Delay of Same‐Beam VLBI in Rendezvous and Docking of Chang'E‐5

“…SBI is an observation method that uses the main beam of a radio telescope to simultaneously observe two adjacent probes at a small angular distance. In these observations (Chen et al., 2011; Liu et al., 2010), differential phase delay (DPD) data between the two probes were obtained due to the small angular distance between the two probes. The atmospheric delay, ionospheric delay, and equipment internal delay are all well eliminated by differential processing.…”