Gravity field from GRACE and SLR data

Abstract:

Due to issues with large tide-like variations in the GRACE estimates for C20, they are usually replaced by the estimates derived from satellite laser ranging (SLR) for better orbit fits and studies of the mass transport within the Earth system, in particular for mass changes of the polar ice sheets. Instead of simply replacing C20, we present a time series of monthly gravity field solutions complete to degree and order 60 from a weighted combination of GRACE and SLR data from five geodetic satellites (LAGEOS-1 and -2, Starlette, Stella and Ajisai). In the solution, the estimate of C20 and geocenter (equivalent to the degree-one geopotential coefficients) are based on the SLR data only; the GRACE contribution to C20 is not allowed to influence the combination. The combination of GRACE and SLR data improve the separation of C20 from the effects of the higher degree zonals. There is also evidence that the estimates of the resonance coefficients are improved. Detailed analysis will be presented in this paper.