GRACE time-varying gravity field solutions based on PANDA software

Abstract

The conventional dynamic approach for gravity filed modelling has been implemented in the PANDA (Position and Navigation Data Analyst) software. A variant of the so-called ‘two-step’ method for gravity field modelling is adopted for this purpose, where the GRACE (Gravity Recovery and Climate Experiment) orbits are derived from the GPS (Global Positioning System) data in a first step followed by a simultaneous determination of dynamic orbit and gravity filed from the GPS-derived orbits and K-band range-rate measurements in a second step. In this way, the monthly gravity field solutions complete to degree and order 96 are produced for the period Jan. 2005 to Dec. 2010. Their performance is assessed by comparing them with the official solutions, i.e., CSR RL05, GFZ RL05a and JPL RL05. A comparison in the spectral domain in terms of geoid heights reveals that the obtained solutions present the smallest degree amplitudes at degree 30–75. A further analysis of mass changes in the spatial domain demonstrates that the main signals observed from the obtained solutions are in great agreement with those from the official solutions. Remarkably, the correlation coefficients of mass changes in large river basins from the official solutions with respect to those from the obtained solutions are all above 0.97. These results demonstrate that the obtained solutions are comparable to the official solutions.