Perturbation Analysis Of Spacecraft Formation Flying Around Halo Orbit

Experienced with a short period of inactivity in the 1980s, the international space community has seen its second boom of deep space exploration from the 1990s. The use of Lagrange point has a good prospect in deep space exploration. NASA and ESA have performed a number of space plan using Lagrange point, which contains a wealth of dynamics and control issues.Dynamics of Lagrange point and periodic orbit around it in the circular restricted three-body system is studied in this thesis. The regions of possible motion and practical application were analyzed according to the energy surface in the circular restricted three-body system. The solar gravitation perturbation was considered in Earth-Moon system for Circular Restricted Three Body Problem (CR3BP). First, the approximate initial values for the orbit around L2 were generated from the Lindstedt-Poincare method described by Richardson, and were corrected by differential corrections to gain high-precision initial values of which the precision can reach to more than 10-14. Then according to the symmetry of the dynamical equation, closed orbit around L2 was gained by integrating along negative and positive direction of time respectively. A sliding mode controller was designed according to the characteristic of the model, in order to track this closed orbit. Numerical simulation results show that, this controller can quickly eliminate the declination of position and velocity when getting in the orbit, and make the spacecraft fly stably in the orbit. In order to contrast, another control method for orbit keeping by pulse was designed. According to the target orbit designed, the appropriate moment on the pulse was selected, while the value and direction of the pulse was calculated. But it's difficult to carry out this method of orbit keeping, because it needs strict requirements on celestial bodies period and calculating accuracy. The results compared showed that, the low thrust control is more suitable for space missions near the Lagrange point, whether the stability or the application in engineering.On the basis of single spacecraft orbit control, further study on spacecraft formation near the Lagrange point continued. The circular formation keeping and reconfiguration was analyzed referred to control method of the single spacecraft. When the period for the follower spacecraft around the chief one is equal to the period for them around Lagrange point, the movement is similar to the relative motion on different Halo orbit. To contrast, analysis of the relative motion of different orbital was made, and the law of change in relative position on different Halo orbit was summed up.The result of this thesis may be applied to fixed point observation or relay station towards the back of moon.