CoAuthors

Stéphane Bourgogne (Géode&Cie, France); Sean Bruinsma (CNES, France); Pascal Gégout (CNRS-UMR5563, France); Franck Reinquin (CNES, France); Richard Biancale (CNES, France)

The gravity field model EIGEN-GRGS.RL03-v2.MEAN-FIELD has been chosen to be part of the new GDR-E standards. EIGEN-GRGS.RL03-v2.MEAN-FIELD is complete to degree and order 260. It is based on GOCE-DIR5 for the part between degree 81 and 260. The time-variable gravity (TVG) coefficients between degrees 1 and 80 are obtained from a regression on the GRGS-RL03-v2 monthly time series (2002.5-2014.5). For degree 2 this TVG part is extended to 1985-2014.5 through the use of a GRGS SLR-only (Lageos+Lageos-2) solution between 1985 and 2003. Outside of the measurements period (1985-2014.5 for degree 2, 2003-2014.5 for degrees 3 to 80), the gravity field is extrapolated with a zero-slope assumption. The modeling of the TVG part includes for the first time two annual and two semi-annual coefficients for each year, in addition to one bias and one drift for each year.
We propose to explain here the way this model has been computed, to describe the TVG coefficients that are included in the model and to discuss the zero-slope assumption that is used for extrapolation. Since this assumption is not satisfactory on the long term, we will propose a method for a regular update of the extrapolated part.