Research On Angles-only Relative Orbit Determination Algorithms For Spacecraft Autonomous Rendezvous

With the development of space technologies,autonomous rendezvous has become a strategy hi-tech and is being more attractive.One of the most important key enabling technology is the orbit determination based on on-board sensors.Further,angles-only relative orbit determination is now becoming one of important research direction of this field.Angles-only relative orbit determination algorithms for spacecraft rendezvous are studied in this dissertation.The main research work and results are as follows:(1)Linear covariance analysis is conducted to the Angles-only initial relative orbit determination prototype algorithm while camera offset from chaser's center of mass supplies the state observability.Firstly,Clohessy-Wiltshire equations are utilized to derive analytic solution for angles-only initial orbit determination.Secondly,camera installation error model,line-of-sight measurment error model and other error models are established,based on which the linear covariance analysis is done to obtain analytic expression for the estimate error mean and covariance.Lastly,a two-body dynamics Monte Carlo simulation frame is construted to evaluate the performance of prototype algorithm and associated closed-form covariance equations.The sensitivity of the solution accuracy to relative trajectory,offset distance and et al is presented and discussed.(2)State augmentation algorithm for angles-only initial relative orbit determination based on camera offset is developed.Closed-form expression for the angles-only initial relative orbit determination is derived by taking advantage of state augmentation least square method based on Clohessy-Wiltshire and Tschauner-Hempel respectively.Linear error covariance analysis is done to get the error mean and covariance for the initial orbit estimation.Two-body dynamics Monte Carlo simulations are conducted to evaluate the performance of the closed-form relative state estimation algorithms and associated closed-form covariance equations.The sensitivity of the solution to spacecraft trajectory,measurement period,camera accuracy,and et al is presented and discussed.And it is verifed that the introduction of high-order dynamics and state augmentation leads to a more accurate solution by comparing with the results of the prototype algorithm.(3)Angles-only initial relative orbit determination algorithms based on distribution method are studied.Three different measuring schemes,i.e.,distribution measuring by a third spacecraft,virtual distribution measuring and distribution measuring by a double spacecraft formation are proposed through analyzing the potential circumstances during the rendezvous mission.The closed-form solutions are derived for the initial orbit determination problem.The relative state observability is analyzed and the analytic expressions of the observable geometry conditions are obtained.Linear error covariance analysis is to get analytic error mean and covariance conducted for the initial orbit solutions.The proposed schemes and algorithms are verified and tested by two-body dynamics Monte Carlo simulations.The sensitivity of the solution accuracy to distribution geometries,measurement period,observation number and et al is presented and discussed.(4)The angles-only relative navigation problem based on camera offset is studied.Simplified observation model,sensors installation error model and et al are established,associated with which relative navigation filtering model is construted based on unscented kalman filter.A novel 'analogous linearity' transformation is conducted to the observation model and then the state observability analysis is done,and the observable conditions are obtained respectively for the cases of Clohessy-Wilshire and Tschauner-Hempel dynamics.The proposed algorithm is verified and tested through five classical nature relative orbits in the frame of two-body dynamics Monte Carlo simulation.(5)Angles-only relative navigation algorithm integrated with relative guidance is studied.A simplified observation model is established and then it is conducted by 'analogous linearity' transformation to do the state observability analysis.The observable conditions are analytically derived.Multi-pulse sliding guidance laws for rendezvous are designed based on Clohessy-Wilshire and Tschauner-Hempel dynamics respectively.The coupling relationship between angles-only relative navigation and the sliding guidance is mathematically analyzed,based on which and unscented kalman filter a novel angles-only closed-loop guidance scheme is designed.The proposed scheme is verified and tested by two-body dynamics Monte Carlo simulations.The sensitivity of the solution accuracy to initial separation uncertainties,number of pulses,initial navigation uncertainites and et al is presented and discussed.