BRIDGE: A small scientific satellite for geodesy

The results obtained from a preliminary scientific mission study realized by a small satellite in low Earth orbit and using DORIS (Doppler Orbitography and Radiopositioning Integrated from Space) is summarized. Scientific objectives are exposed: Earth gravity field, satellite orbit analysis, ionosphere, and thermosphere density variations are to be studied. The principle of the DORIS system is explained and DORIS is described in detail as well as measurement processing. The BRIDGE mission analysis involves the orbit selection from the on-orbit lifetime, the orbit characteristics, launching, satellite visibilities, constraints due to the payload and to the platform. Finally one circular and two elliptical orbits are selected. Platform predimensioning is discussed. Linking and mass budgets are presented as well as the BRIDGE platform stabilization system.