1. Space Research Institute of Russian Academy of Sciences Moscow Russia
2. Université Versailles Saint‐Quentin, LATMOS Guyancourt France
3. Department of Mechanics and Mathematics Lomonosov Moscow State University Moscow Russia
4. Institute for Problems in Mechanics Moscow Russia
5. GEPI/Observatoire de Paris Meudon France
6. Lunar and Planetary Laboratory University of Arizona Tucson AZ USA