定点在日-地(月)系L1点附近的探测器的发射及维持

On the Transfer and Control of Spacecrafts Around the L1 Point of the Sun-Earth+Moon System

在限制性三体问题中共线平动点附近的运动虽然是不稳定的,但可以是有条件稳定的,该动力学特征使得一些有特殊目的的探测器只需消耗较少的能量即可定点在这些点附近(如ISEE-3、SOHO).以日-地(月)系的L1点为例,根据其附近的运动特征,探讨定点探测器的发射与轨道控制问题,给出了相应的数值模拟结果,为工程上的实现提供理论依据.

The fixed configuration with the two primaries and constant thermal environment of the collinear libration points in the sun-earth＋moon system make them ideal places for space observations. Spacecrafts can be sent around them to observe the sun and the earth constantly. Although these benefits of collinear libration points are alluring, the motion around them suffers from the problem of strong instability. Luckily, there exist conditionally stable orbits around them, and these stable orbits can survive under perturbations in the real sun-earth＋moon system. Generally, they can be found using numerical algorithms with the results in the Circular Restricted Three-Body Problem as initial guesses. These conditionally stable orbits can be used as the nominal orbits of the spacecrafts. When spacecrafts are inserted accurately into these orbits, they can keep moving around the collinear libration points without maneuvers. However, due to the error of control and observation, the actual orbit will deviate from the nominal orbit. These deviations will increase nonlinearly with time due to the strong instability of the collinear libration points. So during the lifetime of the spacecrafts, constant control is necessary. Besides the problem of instability, the large distance between the collinear points and the earth makes the transfer of spacecrafts to these points energy-consuming and time-consuming. How to find the transfer orbit is also a critical problem. In this paper, we take the L1 point of the sun-earth＋moon system as an example and study the problems of transfer and orbit control of the spacecrafts. Our strategies are given out and the numerical simulations are made.