[G03-2] Time-varying gravity field estimation

[G03-2-06] Using Swarm and Sentinel observations for time-variable hl-SST gravity field determination

^○Christoph Dahle^{1, 2}, Daniel Arnold², Adrian Jaeggi², Ulrich Meyer², Rolf Koenig¹, Grzegorz Michalak¹, Karl Hans Neumayer¹ (1.GFZ German Research Centre for Geosciences, Potsdam, Germany, 2.Astronomical Institute, University of Bern, Bern, Switzerland)

Equipped with geodetic-grade on-board GPS receivers and star trackers, the three satellites of the Swarm mission can be used to determine the long-wavelength part of the Earth's gravity field including its time variations by means of high-low satellite-to-satellite tracking (hl-SST). This is also true for ESA's Sentinel satellites, although their slightly higher orbital altitude degrades their sensitivity to the gravity field. Hl-SST based gravity field solutions are of special interest to fill the gap between the dedicated gravity missions GRACE and GRACE-FO.

In this contribution the latest results obtained at the Astronomical Institute of the University of Bern (AIUB) as well as at the German Research Centre for Geosciences (GFZ) are presented focusing on the following topics: (1) Systematic errors in Swarm gravity field solutions along the Earth's geomagnetic equator caused by ionospheric disturbances and their mitigation by GPS data screening and/or updated tracking loop settings of the GPS receivers. (2) Comparison of monthly AIUB and GFZ Swarm solutions that are generated with different approaches. (3) Added value of Sentinel-1A, -2A, and -3A satellites (which are not affected by the aforementioned systematic degradations) to the very low degrees of the Swarm gravity field solutions.