飞行器近小行星轨道动力学的特点及研究意义

The Characteristics of Near Asteroid Orbital Dynamics and its Implication to Mission Analysis

该文在介绍小行星及对其探测意义的基础上,以NEAR、Muses-C(Hayabusa)小行星探测器为例,重点分析了飞行器与小行星距离较近时(near asteroid)的动力学环境及其对环绕小行星飞行的飞行器设计的影响.并以旋转的二阶二次重力场和小行星Castalia为例,进一步阐述近小行星轨道动力学的一些特点和结论。此外,还给出了小行星探测的一些建议和设想.

Asteriods and some significance of their exploration are presented first. Near asteroid dynamics and its effect to mission analysis are analyzed by referring spacecraft NEAR and Muses- C. Further discussions of the dynamics characteristics are performed. Detailed discussions are given based on the analysis of the second order and degree gravity field models of asteroids. A typical example of asteroid, Castalia, is introduced. A few typical trajectories are summarized. And also some suggestions of asteroid exploration are given. We see that close asteroid orbital dynamics is new and challenging, as orbits around asteroids are considerably different from the classical Keplerian orbits in the two-body problem. This is due to two reasons： the irregular shape of an asteroid, and the rotation of the asteroid. These two effects are coupled and can cause the spacecraft orbit to experience large energy and angular momentum changes within short time period, occurrence that are not seen for spacecraft motion around the Earth , or other planets in Solar system. For some cases these changes are rapid, making the spacecraft motion unpredictable to some degree, the unpredictability is an instance of chaotic motion, which exists in many dynamics. Here we define ＂Chaotic＂ motion as sensitive dependence on initial conditions. Thus, the problem of spacecraft motion around an asteroid is not only a practical engineering problem of near asteroid operation, but also a theoretical problem in dynamical system as well.