Orbit and Formation Control for the Next Generation Gravity Mission**Part of this research was carried out within the study Next Generation Gravity Mission (NGGM): AOCS Solutions and Technologies study and within the ESA Networking Partner Initiative (NPI) PhD project Laser Metrology Spacecraft Formation (Ref. 4000109653/13/NL/MH) funded by the European Space Agency; Thales Alenia Space Italy (Turin) being the prime contractor