Research On Some Strategies For Computation Of GRACE Atmospheric De-Aliasing Models

Due to the spatio-temporal sampling characteristics of GRACE gravity satellite signals and orbits,the high-frequency mass changes in the atmosphere and ocean will affect the accuracy of the earth's gravity field.And it is easy to mix this part of the signal into the GRACE observations,so it is necessary to eliminate the high-frequency nontidal atmospheric and oceanic mass changes in the inversion of the earth's gravity field,and deduct them as a background perturbation model in the process of orbit determination and inversion.In this paper,the atmospheric treatment process of AOD1 B RL05 is realized,and the surface atmospheric pressure,reference frame,radial coordinates,reference ellipsoid radius,earth average radius,geometric height and space gravity acceleration are adjusted and improved to generate the improved atmospheric treatment process,and its calculation process is introduced in detail.The accuracy of the five spherical harmonic analysis methods is verified by using the principle of closed-loop simulation,and the results show that the accuracy of the least square spherical harmonic analysis is the highest,and the ability of the five spherical harmonic analysis methods to resist errors is verified.The results show that the first kind of Neumann spherical harmonic analysis methods has the strongest ability to resist errors,but the effects of different spherical harmonic analysis methods do not need to be considered for the current solution accuracy of GRACE.A new atmospheric de-aliasing model SWJTU1,is calculated by using ERAInterim data and the improved vertical integration method.The time resolution of the model is 6 hours,and the spherical harmonic expansion is 180 degree.The differences between SWJTU1 and AOD1 B RL05 and AOD1 B RL06 are compared and analyzed from many angles.The results show that the spatial difference between SWJTU1 and AOD1 B RL06 is within the height of 2mm geoid,and the quality of SWJTU1 is better than that of AOD1 B RL05.In view of the large amount of calculation of the conventional atmospheric vertical integral average and the time-consuming calculation of a single atmospheric de-aliasing model,a method of using atmospheric monthly mean data to calculate the average value is proposed in this paper.The quality of the atmospheric de-aliasing model calculated by this method is the same as that calculated by the traditional method,and the difference between them can be ignored.Based on this method,another atmospheric de-aliasing model SWJTU2,which is calculated by using ERA5 data,and the time resolution of this model is 1 hour,and the spherical harmonic expansion is 180 degree,which is equivalent to the mass of AOD1 B RL06,but the time resolution of SWJTU2 model is 3 times that of AOD1 B RL06,which can further weaken the inter-satellite ranging error in gravity field inversion,and has better reference significance for the next generation gravity satellite mission.In addition,this paper also studies the influence of the average value of different time spans on the atmospheric de-aliasing model.The result shows that the influence of different average value can not be considered for the highest accuracy of GRACE gravity field model,but it is necessary to consider its influence in order to achieve the accuracy of the next generation gravity satellite.