Analysis of Zero-Difference Kinematic POD for GRACE

We introduced the principles and influencing factors of the zero-difference kinematic POD,and analyzed the impacts of GPS orbits and clock products on the kinematic POD of GRACE.The results indicate that the precision of the kinematic orbits of GRACE is at the same level for the IGS precise ephemeris and the rapid ephemeris,which means that the precision of the GPS orbits have no influence on the GRACE's kinematic orbits.When using high-rate clock products with 30 s and 5 s interval,the RMS in radial direction are 3.8 cm and 3.4 cm respectively,which indicates that high-rate clocks product can improve the precision of kinemaitc orbits.