Spacecraft's Orbit Improvement Based-on Orbital Dynamics

Orbit determination is the base for spacecraft to accomplish its mission,so it is of great importance.Now most conventional spacecraft can achieve high accuracy of orbit determination with its navigation system.However,deep space exploration,manned asteroid exploration are becoming hot spot in the aerospace field,so relating autonomous navigation are receiving more and more attention,with the development of aerospace technology.Lack of the support of ground station,autonomous navigation have not yet achieve the same accuracy of orbit determination as conventional navigation methods,resulting in that autonomous navigation can't meet the requirement of space mission.As a result,it has great significance to study the improvement of orbit determination with the background of autonomous navigation.The method of orbit improvement based-on orbital dynamics presented by this thesis introduced the concept of ‘pseudo relative motion' and error neutralization,combining the Fourier transform and curve fitting methods,to improve the accuracy of orbit determination on the base of initial orbit determination.First,the observability of relative motion equations under circular orbit and ellipse orbit has been proved,which proved the feasibility of the method applied into improving the accuracy of orbit determination.Then,the improvement of orbit determination under circular orbit has been studied.The pseudo relative motion is accord with CW equations without no perturbations and the modified CW equations with considering J2 perturbation.Then four kind of noises are added into the relative motion equations to imitate the real noise in initial orbit determination.After the influence patterns have been studied,the real noise is been processed and finally improved the accuracy of orbit determination successfully.To extend the application of this method,the improvement of ellipse orbit determination has been studied after the improvement orbit determination under circular orbit.It has the same methodology with the improvement of orbit determination under circular orbit,except the relative motion equations and the data processing method,which is curve fitting method namely.And finally the orbit determination also has been improved successfully.Finally,the method of orbit improvement based on error neutralization has been studied.The pseudo relative motion used the information of relative motion while the method of error neutralization used the information of absolute motion.When the motion equations in orbit elements replace the relative motion and with the curve fitting method,some useful information has been extracted from the real initial orbit determination data,and finally the accuracy of orbit determination get improved.