利用轨道瞬时根数预报的离轨制动控制方法

针对再入飞行器离轨制动问题，在考虑地球引力J2项摄动及有限推力影响下，设计了一种航天器自主离轨制动控制算法。该算法根据再入点状态约束，确定了离轨过渡轨道的平均轨道根数及其与离轨待命轨道平均轨道根数的关系，从而得到制动参数初值。通过在线数值递推轨迹，实时预报再入点瞬时轨道根数并计算再入点航迹倾角，当预报的航迹倾角满足约束条件时结束制动，并根据再入点纬度幅角误差修正制动起始点，从而修正制动参数。制动过程中，在考虑了J2项摄动影响下实时预报再入点瞬时轨道根数，依据实际任务需求确定关机时机。最后通过考虑初始状态误差、质量误差、推力误差以及姿态误差情况下的蒙特卡洛打靶仿真，分析了不同关机策略的落点散布特性，检验了该算法的自主决策和高精度再入点控制能力。

Autonomous Deorbit Algorithm Based on Osculating Kepler Element Prediction

An autonomous deorbit algorithm is developed in consideration of the effects of J2 perturbation term and finite thrust for orbit reentry vehicle. The algorithm determines the initial deorbit parameters according to the relationship between the mean orbital elements of the transition orbit, which is determined by the conditions of the entry interface (EI), and the mean orbital elements of the initial orbit. The numerical trajectory propagation is used on board to modify the deorbit parameters. The shutdown time is determined by the flight path angle at EI which is calculated from the predicted orbit elements, and the engine ignition time is corrected in order to eliminate the latitude deviation at EI. The osculating Kepler element is predicted during the thruster burning, and the shutdown time is determined according to the actual task demand. At last, the Monte Carlo simulations of different shutdown strategies by considering the initial states dispersion, vehicle mass error, thrust magnitude deviation and attitude error are carried out, which verified the ability of autonomous decision making and the precision of this method.