小天体多目标多模式探测任务设计

Mission design for multi-target and multi-mode rendezvous missions to small bodies

多目标多模式小天体探测具有降低任务成本、增加科学回报的优点,本文针对多目标多模式小天体探测任务中摄动敏感、约束复杂以及推力幅值变化等任务规划的设计难题,研究了地球准卫星采样返回以及主带彗星交会探测任务的转移轨道设计问题.首先,介绍了探测目标的科学价值并根据任务约束给出探测任务构想.其次,基于椭圆型限制性三体问题,考虑星历、发射能量和采样返回再入速度等约束,设计并优化了地球准小行星目标的多脉冲采样返回轨道,实现地球发射与返回段和星际转移段全过程的精确飞行设计.最后,根据任务约束,推导了推力幅值可变的最优小推力转移轨道的一阶必要条件并给出考虑借力约束的初值选取方法.以采样后火星借力探测主带彗星为例,求解并分析了最大推力幅值衰减的小推力交会轨道.本文的研究方法可为我国未来的深空探测任务提供参考.

Multi-target exploration to small bodies has the advantages of reducing mission cost and increasing scientific return. It will be widely used in the future small body exploration missions. This paper investigates the problem of perturbation sensitivity, complicated constraints and changeable thrust, which may be faced in the multi-target exploration mission. The Earth quasi-satellite sampling return and main-belt comet rendezvous missions are studied. First, based on the mission constraints, the mission design schedule and relevant constraints are given. Then, the multi-impulse asteroid sampling return trajectory is investigated in the elliptical three body model. Considering the gravitational perturbation of Earth, the integral trajectory design consist of Earth escape phase, interplanetary transfer phase, and Earth reentry phase is proposed. The trajectory design is divided into two parts. The optimal preliminary transfer opportunity is firstly searched in two-body problem and is transferred to the elliptical three body model. The differential correction scheme is applied to correct the error caused by Earth gravity perturbation. The trajectory for the Earth quasi-satellite 2016HO3 is designed. Finally, considering the engineering constraints, the first-order necessary condition of the changeable lowthrust trajectory are derived, where both the thrust and special impulse change with the distance to Sun. By introducing the B?plane parameters, the initial states determination under the constraint of the gravity assist is developed. Based on the homotopy method, the low-thrust optimal trajectory after Mars gravity assist to the main belt comet 133P are designed and compared with constant low thrust trajectory. The proposed multi-target exploration scheme and the orbit design method can provide a reference for future small bodies exploration missions in China.