Study On GEO Satellite Transfer Trajectory Design And Station Keeping Method

Geostationary satellite is a satellite with rotation direction and orbital period the same as the Earth’s rotation direction and period respectively, which is widely used in communication, meteorology, data relay, navigation and positioning. The functional extendibility of GEO satellite and high standards of navigation system set high requirements for the payload ratio, life and station keeping precision of satellite. Therefore, the design of GEO satellite transfer orbit and method of station keeping is studied in this paper, including the following major parts:For the problem of effectiveness evaluation of current impulse transfer trajectories, a method of evaluating the total velocity increment of trajectories to geostationary orbit is proposed. Firstly, the hybrid optimization algorithm combining DE and SQP is used to obtain global optimal transfer trajectory and generate training samples with orbit elemets as inputs and total delta-v as outputs. Secondly, the GPR model is established by selecting covariance function, which learns the relationship between orbit elements and total delta-v. The numerical results demonstrate that the proposed method can evaluate total delta-v efficiently, taking 5.86 seconds on 100,000 orbits, and average relative error is 0.49%.With respect to the low thrust transfer trajectory of GEO satellite, the influence of earth shadow on the dynamic orbit model is analyzed, and a method of designing low thrust transfer trajectory based on Lyapunov feed-back control law is given. The proximity quotient serves as candidate Lyapunov function of the control law. Then the optimal thrust angles are derived. Numerical results show that the method can obtain low thrust transfer trajectory towards GEO effectively.For the station keeping of GEO satellite, a station keeping method using low thrust based on diurnal prediction is proposed. The feasibility of diurnal station keeping using low thust is analysed based on the principle of GEO drift. The procedure of diurnal prediction and station keeping is given on the basis of four-thruster configuration. For selected position, the gimbaled angle is optimized according to the accuracy of station keeping. The numerical results show that the accuracy of NSSK and EWSK is ?0.01? and ?0.03?, respectively, demonstrating the proposed method is effictive for GEO station keeping.Finally, the station keeping methods of thruster failure mode and combined thruster are studied. A strategy of station keeping under thruster fault is proposed. Using this strategy, the satellite can achieve station keeping with remaining thrusters if any one of the thruters failed. Under the station keeping method of conbined thruster, chemical thrusters and electric thrusters are used in East-West and North-South station keeping respectively. Numerical results demonstrate that the proposed methods are effective in station keeping, and the accuracy of station keeping are controlled in ?0.05?.