| Lunar exploration constellation refers to the constellation which is established in lunar orbit and Earth-Moon libration point orbit.It can be used to provide continuous coverage for the specific areas or even the entire lunar surface.Lunar exploration constellation could provide the necessary relay communication,navigation,positioning and other functional support for comprehensive lunar exploration in the future.In this paper,the design of the lunar exploration constellation orbit is studied,including problems such as transfer orbit design,midway correction,capture deployment,constellation configuration,orbital maintenance,etc.The main research results are as follows:Firstly,considering the influence of the lunar nonspherical perturbation,the design method of frozen orbit is proposed.Meanwhile,in view of the constellation configuration design problem,the lunar constellation configuration satisfying the task constraint is designed with the coverage angle of lunar center and orbit phase parameters.Besides,a new method using improved double limit cycles is developed for constellation orbit keeping,which effectively avoids the problem of frequent switching shock control.Secondly,to design the Earth-Moon transfer orbit for lunar constellation satellite,positive and reverse design methods are given with different design requirements.Based on this method,the launch window which satisfies engineering constraints has been searched.The finite thrust method for capture orbit design of lunar exploration constellation is based on multi-pulse initial guess and homotopy method.Meanwhile,considering the constraints between the parking orbit and the mission orbit,the constellation deployment transfer trajectory based on finite thrust method is designed.In addition,to minimize the injecting and measuring errors,midway correction strategy during Earth-moon transfer is obtained by the ground measurement and control conditions.Thirdly,aiming at the location of the lunar relay satellite,the types of mission orbit of the satellite were selected by the condition of the relay communication link.Based on the results,Earth-Moon libration point transfer orbit for relay satellite is researched.According to engineering constraints and taking the result of the ideal restrictive three-body model as the initial value,lunar flyby transfer trajectory is obtained by reverse segment splicing under ephemeris model based on the theory of invariant manifolds.The lunar flyby transfer trajectory for Halo orbit around Earth-Moon L2 point with different amplitudes is given using the proposed method.Due to the errors of measurement and control,midway correction strategy is developed for libration point transfer.Furthermore,taking the amplitude constraints into consideration,a correction strategy for Halo orbit with low-cost is devised.Finally,in view of the task required,the moon poles,specific areas and entire lunar surface exploration constellation are established respectively.The different constellation schemes are designed by combining Earth-Moon libration point relay satellite orbit with lunar exploration constellation.And the analysis of its coverage and communication performances have been assessed and compared. |
