Dynamic Smoothing Of Low-orbit Satellite Geometric Orbit

With the expansion of the field of satellite application,the application of satellite GRACE in low orbit gravity field has been fully developed,and higher requirements have been put forward for the accuracy of satellite orbit.Among them,the geometric legal orbit of low orbit satellite is closely related to the GPS satellite visible number,geometric composition,coarse difference,circumferential jump and other factors,while the GPS satellite visible number and geometric structure are dynamic changes,which will lead to the fluctuation of geometric orbit determination accuracy and the orbit accuracy is not very stable.On the basis of geometric orbit,establishing appropriate satellite dynamic equation and smoothing geometric orbit by dynamic method can weaken the accidental error in orbit and improve the accuracy of orbit.At the same time,the continuity of orbit can be guaranteed,and the position of low-orbit satellite can be given at any time by orbit integration.This paper mainly analyzes he analysis of the influence of the modeling method of the background perturbation dynamic error model on the GRACE orbit dynamics of low-orbit satellites,the reduced dynamic orbit and the geometric orbit are used as the observed values,respectively,and the dynamic model is used to smooth it.First,the geometric orbit and observation data of low-orbit satellites are pretreated,then the state transfer matrix and parameter sensitive matrix are calculated by numerical integrator.Each arc segment has satellite initial orbit error and perturbation parameter deviation.The local parameter elimination method is used to solve the parameters to be estimated,the initial state and perturbation model of the satellite are corrected,and the smooth orbit is obtained by re-integrating.The scale factor,deviation model and estimation time of the measured acceleration of non-conservative force are analyzed.The results show that:With the shortening of the estimation time of the deviation parameters,the smaller the residual error of the integral GRACE satellite orbit,in which the estimated time is 15 minutes,the scale model is diagonally filled,the highest accuracy of the satellite orbit is obtained when the order of the deviation model is 1 order,the residual value in the X、Y and Z directions is 0.5 mm compared with the reference orbit,and the orbit residual increases gradually when the integration time is less than 15 minutes;Analysis of the deviation model shows that when the deviation estimation time increases,the accuracy of the GRACE geometric orbit smoothing can also be improved by selecting the higher order deviation model.For the influence of the estimation time and the parameter model,the estimation time has a significant effect on the results of the orbit smoothing;For the setting of scale model,it can be seen that the scale model type setting is less than the influence of deviation parameter and estimation time on orbit.the scale model with full filling should be used when the estimation time is longer.The scale model with diagonal filling can be used for short estimation time or the influence of scale parameter on orbit is not considered.When the GRACE satellite geometric orbit is smoothed as the observed value dynamics,the deviation parameter estimation time is 15 minutes,the scale model is diagonally filled,and the RMS between the smoothed orbit and the JPL published reduced dynamic orbit in three directions is 1.41 cm,1.34 cm,1.28 cm.By shortening the estimation time of the deviation parameters and selecting the estimation strategy of the scale model with diagonal filling,the accidental error of the geometric orbit will be effectively weakened and the orbit accuracy will be improved.