IGG-SLR-DORIS: Monthly gravity field solutions from SLR and DORIS

IGG-SLR-DORIS is a series of GRACE-like gravity field solutions going back to 1984 based on tracking data to up to 16 satellites, observed either by satellite laser ranging (SLR) or by means of the Doppler Orbitography and Radiopositioning Integrated by Satellites (DORIS) system. The match with GRACE in spatial resolution is achieved by representing the gravity field by empirical orthogonal functions (EOFs) obtained by a principal component analysis of the GRACE/GRACE-FO solutions. To make the modelling more adaptive, the EOFs are supplemented by low-degree spherical harmonics. IGG-SLR-DORIS is intended to replace the previously released IGG-SLR-HYBRID solution which applied the same parametrization. It could be shown that the combined SLR/DORIS solution is clearly superior, reducing the average difference to the GRACE/GRACE-FO fields by 10.6 percent. As another enhancement, the beginning of the time series was advanced by eight years by extending the analysis to historical SLR data. The time series now also includes a degree-1 solution based on an own inversion approach and using the surface mass distribution from the SLR/DORIS fields.