Research On Satellite Cluster Flight Based On Quasi-nonsingular Relative Orbital Elements

Satellite cluster,which is formed by multiple member satellites flying stably in near Kepler orbit for a long time and linked via inter-satellite wireless communication network,is a new concept of distributed space system with resource sharing capability.Compared with monolithic spacecraft,the advantage of satellite cluster system is robustness and flexibility.Compared with traditional distributed satellite system,satellite cluster system has the advantages of less maneuver cost,long-term in-orbit operation and less technical risk,thus representing a future direction for distributed satellite system.At present,the research on key technologies of satellite cluster has important theoretical value and practical significance.Cluster flight,space wireless communication&self-forming network and space distributed computing are three key technologies of satellite cluster system.On the basis of the relative motion model described by quasi-nonsingular Relative Orbital Elements(ROEs),this paper focus on the cluster flight issue of satellite cluster system operating in near-circular reference orbit and adopting cluster-tree network topology.Firstly,the relative motion modeling of satellite based on quasi-nonsingular ROEs is studied.Based on the relative motion state represented by quasi-nonsingular ROEs,the relative motion equation without considering perturbation is derived.Two models based on quasi-nonsingular ROEs,are introduced for relative motion modeling under effects of non-spherical J₂ perturbation and differential atmospheric drag perturbation.The Gauss variational equation expressed by quasi-nonsingular ROEs is obtained by an inversion of the linear relative motion equation without perturbation.Based on this equation,two strategies for relative orbit control based on three impulsive maneuvers are proposed.The concept of relative E/I vector separation is introduced,and its relationship with passively safe and collision avoidance is analyzed.The principle of local rigidity is proposed and proved,and its value for cooperative control of multiple satellites is explained.Secondly,the safe deployment strategy for satellite cluster is studied.Based on the relative motion model described by quasi-nonsingular ROEs,the relative motion characteristics between Launch Vehicle(LV)and Released Satellites(RSs)during the in-orbit separation process are analyzed.According to the safety requirements of relative motion between LV and RSs,a safety concept design is proposed.Then,the sefe deployment issue is transformed into a feasible solution problem in a constrained relative E/I vector space.In order to solve this problem,a geometric method is developed to obtain the safe release parameter sequence.To evaluate the effect of release uncertainties,the worst-case analysis method based on interval algebra is presented,and an adaptive improvement scheme to deal with release uncertainties is proposed.A simulation scenario is designed on the base of the deployment process for the SAMSON mission,and the simulation results verify the feasibility and effectiveness of our method.Thirdly,the guidance and control issue of satellite cluster during the cluster maintenance phase is studied.For the two control object in the process of satellite cluster maintenance–network topology maintenance and collision avoidance,the corresponding guidance/control methods are proposed respectively.Specifically,on the one hand,according to the principle of local rigidity,a guidance/control algorithm for topology maintenance of cluster network,based on the cooperative adjustment of semi-major axis for each member satellite,is developed.On the other hand,according to the principle of relative E/I vector separation,a guidance/control method for collision avoidance between cluster satellites is presented based on the cooperative adjustment of relative E/I vector between each member satellite.The effectiveness of the above two methods is demonstrated by numerical simulation cases.Fourthly,the guidance and control issue of satellite cluster during the cluster operation phase is also discussed.The concepts of typical cluster operation scenarios are defined at first.Then,on the basis of the cluster maintenance technology developed in Chapter 4,the guidance/control method to regulate the relative distance of critical cross-links in cluster is present,by the cooperative adjustment of semi-major axis for each member satellite.Simulation results show the effectiveness and applicability of the above guidance/control methods in various cluster operation scenarios.Fifthly,the ground test-bed for satellite cluster system is designed.In order to solve the problem that the existing Commercial-Off-The-Shelf(COTS)simulation softwares are difficult to support the modeling&simulation function for the dynamic and network communication process independently and simultaneously,the test-bed architecture is proposed by ultilizing the built-in Esys module of OPNET Modeler,which realizes an effective integration of OPNET Modeler,STK and Matlab simulator resources.The feasibility and effectiveness of our design are demonstrated by the simulation scenario of space-based ad hoc network realized by the Zig Bee protocol.In a word,based on the theory of quasi-nonsingular ROEs,this paper studies the issues of safe deployment,long-time cluster maintenance and cluster operation for heterogenrous satellite cluster system in near circular reference orbit.The corresponding solutions for each issue are presented,and a ground test-bed for satellite cluster system is developed.The research work in this paper can provide reference for the theoretical research and engineering application of satellite cluster missions in the future.