Improved GPS receiver clock modeling for kinematic orbit determination of the GRACE satellites

Kinematic orbit positions of Low Earth Orbiting satellites (LEOs) derived from GPS observations are frequently used for single satellite gravity field recovery. Unfortunately, the precision of the kinematic coordinates is compromised by the estimation of the receiver clock synchronization offset in addition to the three kinematic coordinates for every observation epoch. In this paper the potential of receiver clock modeling to improve the precision of the kinematic orbit determination is investigated. The formation flying twin satellites of the Gravity Recovery And Climate Experiment (GRACE) mission are considered as a case study. A unique feature of these satellites is the combination of a dual frequency GPS receiver with an Ultra Stable Oscillator (USO), that provides the required frequency stability for the proposed clock modeling approach. Based on a piece-wise linear clock parametrization with 60 s intervals, a significant reduction of the high-frequency radial orbit differences with respect to a reduced-dynamic orbit is shown.