月面起飞基准高精度标定技术应用与嫦娥五号任务验证

Application of a high-precision calibration technology for lunar liftoff and verification using Chang’E-5 mission

嫦娥五号探测器于北京时间2020年12月1日成功着陆于月球表面预定区域,随后依次顺利完成了我国首次月面采样、月面起飞、月球轨道交会对接以及月球采样返回.其中,对着陆上升组合体精确定位是后续能否顺利月面起飞,乃至能否顺利完成月球轨道交会对接的根本所在.本文针对嫦娥五号任务着陆上升组合体月面起飞基准高精度标定的需求,提出了利用"三向测量系统+VLBI干涉测量系统"的高精度月面基准测量方法,给出了月面基准高精度确定算法,利用嫦娥五号任务20 min实测数据快速确定了着陆上升组合体在月固系下的坐标为:43.0595°N,-51.9214°E,高程-2446 m,并利用LRO图像数据对定位结果进行了比较评估.结果表明,仅利用着陆后20 min的外测数据获得的定位结果和LRO图像数据差异为180 m,当只解算经度和纬度,高程由月面数字高程模型获取时,其定位结果和LRO图像数据差异为97 m,可有效作为月面起飞基准.利用月面48 h实测数据得到的坐标为:43.0594°N,-51.9167°E,高程-2550 m,和LRO图像数据差异为60 m.

Chang’E-5 explorer landed on the lunar surface on December 1, 2020, Beijing time, completed China’s first lunar surface sampling, lunar surface liftoff, and lunar orbital rendezvous and docking, and then returned to the Earth successfully.Accurate positioning of the lander and ascending vehicle assembly are the key to the success of lunar liftoff and as well as lunar orbital rendezvous and docking. Aiming at fulfilling the requirement of high-precision calibration of lunar liftoff of the lander and ascending vehicle assembly of Chang’E-5 mission, the method of using a "three-way ranging and Doppler system + VLBI interferometry system" to realize high precision of a landing position is proposed herein. Then, a high-precision determination algorithm for the lunar liftoff datum mark is provided. Using 20-min observables of Chang’E-5 mission after landing, the landing location of the lander and ascending vehicle assembly could be calculated rapidly, which was 43.0595°N and-51.9214°E, having a-2446-m elevation. Results showed that the difference between the positioning results obtained using the tracking data only 20 min after landing and the lunar reconnaissance orbiter(LRO) image data provided by NASA was 180 m. When only longitude and latitude were calculated and elevation was obtained from the lunar digital elevation model, the difference between the positioning result and LRO image data was97 m, which could be effectively used as the lunar surface liftoff datum mark. Using 48-h observables after landing, the landing location of the lander and ascending vehicle assembly was 43.0594°N and-51.9167°E, having a-2550-m elevation, with a difference of only 60 m compared with the results of LRO.