嫦娥五号平动点拓展任务轨道方案研究

Trajectory Schemes of Chang’e-5 Extended Missions to Libration Points

中国嫦娥五号探测器成功实现月球采样返回任务,为最大限度利用任务资源,研究了利用嫦娥五号轨道器的平动点拓展任务轨道方案,设计了平动点轨道及其转移轨道。首先,给出了任务轨道设计的轨道动力学模型,包括圆型限制性三体问题模型和精确力模型。其次,基于嫦娥二号和嫦娥5T1平动点拓展任务设计经验,介绍了平动点轨道直接转移与入轨等轨道设计方法。最后,基于嫦娥五号轨道器与返回器分离后的状态,设计了包括日地Lissajous轨道、地月Lyapunov轨道和NRHO轨道的平动点拓展任务方案,其中日地Lissajous轨道方案分别考虑了轨道器规避机动至不同近地点高度的情况,地月Lyapunov轨道方案采用月球借力转移方式并且涵盖了地月L1和L2点,NRHO轨道方案包括直接深空机动转移和经日地L1点转移的方式。研究结果表明,拓展任务方案所需速度增量不超过400 m/s,最小为103 m/s,转移飞行时间基本不超过90天,最短为70天,研究方案可为嫦娥五号轨道器拓展飞行任务提供有益参考,实现了我国首次日地L1点探测飞行。

China’s Chang’e-5 spacecraft has successfully completed the lunar sampling and return mission. For the maximal utilization of mission resources, the trajectory schemes of extended missions to libration points are studied in this paper using Chang’e-5 orbiter, focusing on designs of the libration point orbits and the corresponding transfer trajectories. Firstly, the dynamics models for orbit design are presented, including the model of circular restricted three-body problem and the high-fidelity model. Secondly, based on the design experience of Chang’e-2 and Chang’e-5 T1 extended missions to libration points, the orbit design methods of direct transfer and entry of libration point orbits are introduced and employed. Finally, based on the separation state of Chang’e-5 orbiter and reentry vehicle, several extended missions to libration points are designed including Sun-Earth Lissajous orbit, lunar Lyapunov orbit and NRHO orbit. For the scheme of Sun-Earth Lissajous orbit, two cases with different altitudes of perigee after the separation maneuver of orbiter from the reentry vehicle are studied. The scheme of lunar Lyapunov orbit adopts the transfer via a lunar swing-by and consists of the lunar L1 and L2 points. The scheme of lunar NRHO likewise introduces two ways of transfer: one using a deep-space maneuver, and the other passing by the Sun-Earth L1 point. The research result shows that the velocity increment required can be less than 400 m/s and as low as 103 m/s, and the transfer flight time can be less than 90 days and as low as 70 days. The schemes are beneficial to the Chang’e-5 extended mission and lead to the first successful flight around the Sun-Earth L1 point of China.