Gravity Field Modeling on the Basis of Satellite Accelerations Directly Derived from Onboard GPS Measurements

A new gravity field modeling approach is presented.It is based on average satellite accelerations directly derived from onboard GPS phase measurements,i.e.without computing the kinematic orbit as an intermediate product.An advantage of this approach is that no ambiguity resolution is needed,and most of systematic errors that exist at neighboring epochs can be eliminated.GPS data from CHAMP and GRACE satellites covering 101-day interval were processed to recover a model of Earth's gravity field model.The results showed that calculating accelerations directly from GPS measurements improves the quality of the gravity field model by approximately 20%.