环月降轨实现月面着陆的控制策略

针对探测器实现月面着陆的问题，对环月降轨轨道控制策略进行了研究。根据环月降轨的控制方程，将环月降轨单脉冲控制变量的不同组合与月面着陆目标参数建立了3种关系；建立了定时定点月面着陆、定点月面着陆和目标纬度区域月面着陆3种环月降轨控制策略，并给出了控制策略求解算法和步骤。针对定点月面着陆，单脉冲对半长轴和近月点高度进行组合控制，分析了环月降轨控制解空间。针对标称环月轨道/-偏差环月轨道/+偏差环月轨道，分别进行了定时定点/定点/目标纬度区域3种月面着陆的控制计算，验证了环月降轨控制策略。可应用于月球着陆、月球采样返回及载人登月等实施月面定时定点着陆任务的轨道控制。 

Control strategy of lunar orbit descent to achieve lunar landing

Aiming at the problem of the probe's lunar landing, the control strategy of lunar orbit descent is studied. According to the control equations of the lunar orbit descent, the three kinds of relationship between the different combinations of the single-pulse control variables of the lunar orbit descent and the parameters of the lunar landing target are established. Three control strategies for lunar orbit descent, which are the fixed-point landing at the fixed time, the fixed-point landing and the landing at the target latitude area, are established. The algorithms and the procedures for solving the lunar orbit descent control strategies are presented. For the fixed-point lunar landing, the solutions of the single-pulse combined control of the semi-major axis and the lunar perigee height are analyzed. The control calculations of three kinds of lunar landings with the fixed-point at fixed time, the fixed-point, and the target latitude area are carried out respectively for the nominal orbit, the negative deviation orbit, and the positive deviation orbit, and the control strategies of the lunar orbit descent are verified. The strategies can be applied to the orbit control of the lunar landing mission, such as lunar landing, lunar sampling return, and manned lunar landing.