1. Helmholtz Centre Potsdam, Research Center for Geosciences (GFZ), Section 1.2: Global Geomonitoring and Gravity Field, c/o DLR Oberpfaffenhofen, Münchener Strasse 20, 82234 Wessling, Germany
2. Now at Trimble TerraSat, Haringstr. 19, 85635 Hoehenkirchen-Siegertsbrunn, Germany
3. Helmholtz Centre Potsdam, Research Center for Geosciences (GFZ), Section 5.4: Hydrology, Telegrafenberg, 14473 Potsdam, Germany