1. Chair of Astronomical and Physical Geodesy, Technical University of Munich (TUM) , Arcisstraße 21, 80333 München, Germany
2. Physical Geodesy, Technische Universität Berlin , Straße des 17. Juni 135, 10623 Berlin, Germany
3. Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Section 1.2: Global Geomonitoring and Gravity Field , Telegrafenberg, 14473 Potsdam, Germany
4. Max-Planck-Institute for Gravitational Physics (Albert-Einstein-Institute), Leibnitz University Hannover , Callinstraße 38, 30167 Hannover, Germany
5. German Aerospace Center (DLR), Institute for Satellite Geodesy and Inertial Sensing , Callinstraße 30b, 30167 Hannover, Germany