Point positioning geocenter through LEO GPS tracking and its application in geophysics

We introduce geocenter location parameters into the GPS tracking measurement model to represent the offset between the center of mass (CM) of the Earth system and the origin of the Terrestrial Reference Frame being used in the GPS-based precise orbit determination (POD) of lower Earth orbiters (LEOs). The estimated geocenter location parameters become a part of the LEO POD solution. We present daily geocenter locations in the IGS14 reference frame estimated over 19 years from the POD of different LEOs using GPS tracking in different scenarios, such as different spacecraft and orbital configuration with or without accelerometer measurements. The time series of the estimated geocenter location can be used to derive the spherical harmonic degree-1 terms of the Earth surface mass change for global surface mass change studies.