1. Department of Space Technology; University of German Armed Forces; Munich; Germany
2. Department of Reference Systems and Geodynamics; Royal Observatory of Belgium; Brussels; Belgium
3. Department of Planetary Research, Rheinisches Institut für Umweltforschung; University of Cologne; Cologne; Germany
4. Department of Electrical Engineering; Stanford University; Stanford; California; USA
5. CNES, GRGS; Toulouse; France