Champ orbit determination and gravity field recovery Original Research Article

Results are presented from precise orbit computations of CHAMP using a reduced dynamic procedure within the GIPSY/OASIS software. Details are given of the orbital strategy and tuning process for the kinematic stochastic accelerations. The accuracy of the orbits is quantified by overlap residuals, by comparison against independent orbits submitted to the IGS LEO Pilot Project and by use of SLR tracking. GPS derived Cartesian positioning is used as tracking to recover scaling factors and offsets for the accelerometer data, thruster mismatch and misalignment, and gravity field harmonics. A comparison is undertaken of surface forces inferred from the accelerometer data and from modelling. Selected sets of CHAMP positioning and accelerometer data are then used to derive an enhanced gravity field. Precise orbit determination of geodetic and altimetric satellites are compared against existing models and the new field, NCL_champ.2.