In situ gravimetric observables are computed from GRACE inter-satellite K-band ranging (KBR) and GPS measurements, along with non-gravitational accelerations. For time-variable gravity field analysis, residual KBR data could be directly used to approximate gravimetric observables. We study the systematic errors in approximating potential difference, line-of-sight (LOS) gravity difference and LOS gravity gradient with residual KBR data. Based on a simulation study, we show that the approximation errors are significant at the low frequency part of the gravity spectrum for all three observable types. The approximation errors remain below 10% of the signal for the potential difference, LOS gravity difference, and LOS gravity gradient, at frequencies >1 cycle-per-revolution (CPR), >7 CPR, and 7–40 CPR, respectively. Considering the actual error of residual KBR data, it is feasible to accurately compute the gravimetric observables directly from band-pass filtered residual range-rate and range-acceleration data, and employ them for analyses concerning the regional time-variable gravity field of the Earth such as continental hydrology.
GRACE KBR LOS gravity gradient LOS gravity difference Potential difference
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This work is funded by The University of Newcastle to support NASA’s GRACE and GRACE Follow-On projects as an international science team member to the missions.
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