Zero-difference Reduced-dynamic Method Precise Orbit Determination Of LEO Satellite On-board GPS

Low Earth Orbit（LEO）satellites brings revolutionary development stage forearth science, and the precise orbit of LEO is the basis of other scientific research. Atpresent, the widely use of LEO provides a good external environment for thedevelopment of LEO satellite precise orbit determination technology. As one methodof LEO precise orbit determination, zero-difference reduced-dynamic method makesfull use of satellite’s geometry and dynamic information, balances the weight betweendynamic model and GPS observations’ geometry information, and reduces the effectof dynamic model error. The result of orbit determination is stable and with highaccuracy. Therefore, it has some meanings to research the zero-differencereduced-dynamic method.The first part of the paper describes the development of satellite navigationsystem and present research situation of domestic and foreign space-borne GPS LEOprecise orbit determination firstly, introduces the basic theory of satellite precise orbitdetermination, including time systems, coordinate systems and the transform ofdifferent system, describes the none perturbation of satellite,the two-body problemand the satellite’s perturbation, analyzes the effect of each perturbation force andcalculation model, introduces the geometry observation mode of satellite and the mainsource of error and the way of correction.The second part of the paper introduces the basic principle of zero-differencereduced-dynamic method in detail, designs a processing procedure of GRACEsatellite precise orbit determination, adopts31days’ GRACE satellite space-borneGPS observation data from the day213to243of the year of2011, calculates the30days’ reduced-dynamic orbit of GRACE_A and GRACE_B satellites withzero-difference reduced-dynamic method, compares the orbit with the JPL scientificorbit. The result shows that the RMS at the along-track, cross-track, radial directionsof GRACE_A are1.29cm,0.87cm and1.52cm; The RMS at the along-track,cross-track, radial directions of GRACE_B are1.32cm,0.94cm and1.61cm. Both3D-RMS values are2.17cm and2.28cm, the accuracy reaches to the meter level.The last part of the paper briefly introduces the principle of Satellite Laser Ranging(SLR), makes use of the SLR observation data from the day213to243of theyear of2011to check GRACE_A and GRACE_B satellites’ orbit. The result showsthat the RMS of difference between the back calculation station-center distance andthe SLR calculation station-center distance is less than5cm, the GRACE_A andGRACE_B satellites’ average RMS of31days are2.5cm and2.6cm.