月球重力场模型误差对CE-5T1探测器定轨的影响

Analysis of the Effect of Lunar Gravity Field Errors on Orbit Determination of CE-5T1 Spacecraft

利用嫦娥五号再入返回飞行试验拓展任务期间获取的探测器(CE-5T1)实测数据,采用内符合方法比较了3种重力场模型的实测数据定轨结果,发现采用GRAIL(Gravity Recovery And Interior Laboratory,重力恢复与内部实验室)重力场模型进行定轨的结果最优。相比于之前的嫦娥系列探测器定轨常用的LP(Lunar Prospector,月球勘探者)重力场模型,采用GRAIL重力场模型定轨后测距数据的残差降低了1个量级。进一步采用不同重力场模型进行轨道外推,定量分析重力场模型对不同类型轨道的影响,结果表明,对于倾角为90°的环月极轨道,不同重力场模型的轨道外推结果差异较小;而对于倾角为20°和40°的环月轨道,不同重力场模型的外推星历的偏差均方根可达到2km,大于当前环月探测器的定轨精度。为此,建议在后续探月任务中使用GRAIL重力场模型进行轨道确定。

Using the measurement of Chang＇E-5T1 （CE-ST1） probe, the orbit determination results from 3 different gravity field models are compared by the method of internal compliance. It is illustrated that the orbit determination （OD） of Gravity Recovery And Interior Laboratory （GRAIL） model is the most accurate. Compared with the post- fit residuals of OD using LP165P （LP, Lunar Prospector） model which used in past Chang＇E probes, the residuals of range data is improved by an order of magnitude. Furthermore, the difference between orbit extrapolations of 3 gravity field models is quantitatively analyzed. The results show that the model difference is relatively small for 90~ inclination orbit. The Root Mean Square （RMS） difference between orbit extrapolation is about 2 km for 20° and 40° inclination orbits, which is larger than the present accuracy of OD. Based on these results, it is suggested that GRAIL gravity field model should be used in the OD for follow-up lunar orbit probes.