嫦娥三号动力落月段轨迹确定策略

针对CE-3（嫦娥三号）月球探测器动力下降弧段,特别是悬停避障段频繁机动的特点,提出了采用B样条函数逼近方法进行落月轨迹确定.仿真分析表明：在动力下降运动较平滑弧段,B样条逼近法计算结果略优于多项式拟合法;而在频繁机动弧段,B样条逼近法有明显优势.计算结果表明,加入VLBI（Very Long Baseline Interferometry,甚长基线干涉测量）数据后能有效提高落月轨迹确定精度,在没有系统误差的情况下联合定位后位置精度优于50 m.此外,还分析了三向测量系统差对定位的影响,可对CE 3任务提供参考.最后对CE 3实测数据进行处理,动力落月段末点位置和着陆器定位计算值相差不到200 m.

On Trajectory Determination Strategy for Soft Landing of CE-3 on the Moon

A method based on t3 spline approximation is proposed for determination of the landing trajectory of CE-3 （Chang~e-3） probe on the moon based on the feature of frequent maneuvers of the probe in the boosted descending arc and, particularly, during the hovering and obstacle avoidance period. Simulation shows that the method gives a higher precision result compared with the method based on polynomial function fitting in the relatively smooth arc in the boosted descending period and it is significantly better in the arc with frequent maneuvers. Computation results indicate that the adding of VLBI （Very Long Baseline Interferometry） data effectively increases the accuracy in de- termination of the moon-landing trajectory. The position accuracy is better than 50 m after joint trajectory determi nation without systematic error. The impact of the systematic error of three-way measurement on trajectory determi- nation is also analyzed. Finally, the method is tested with data from the CE-3 mission. Compared with the computed location of the lander, the position accuracy at the end point of the boosted descending period is less than 200 m.