Towards Low-Cost Permanent Space-Borne Observation of the Geomagnetic Field and Ionospheric Environment

Space-borne observation of the Earth's magnetic field and of the ionospheric environment started early on in the history of space exploration. But only since 1999 has continuous low Earth orbiting observation successfully been achieved, thanks, in particular, to the Oersted, CHAMP and Swarm missions. These missions have demonstrated the usefulness of long-term continuous observation from space for a wealth of applications, ranging from understanding the fast and small scales of the Earth's core dynamo, to investigations of still poorly understood ionospheric phenomena. In this presentation, we will show that such observations could now possibly be achieved by much cheaper free-orbiting gradient stabilized 12U nanosatellites, such as the "NanoMagSat" nanosatellite concept currently under phase 0 within CNES. Such satellites would not require sophisticated orbit or attitude control, and would take advantage of a miniaturized version of the absolute magnetometer designed by CEA-LETI, which currently operates on the Swarm mission. This instrument is capable of simultaneously providing absolute scalar and vector measurements of the magnetic field at 1 Hz sampling rate, together with higher frequency (250 Hz sampling rate) absolute scalar data. It would be coupled with star imagers for attitude restitution, together with other instruments providing additional measurement capabilities for ionospheric science and monitoring purposes (vector field measurements beyond 1Hz, plasma density, electron temperature, TEC, in particular). Because Swarm will very likely ensure data acquisition on polar orbits for at least another 10 years, a first "NanoMagSat" satellite could be launched on an inclined orbit (within the 60° range) to provide a much-needed fast local time coverage of all sub-auroral latitudes (the so-called "Swarm Delta" mission concept). Beyond this maiden mission, "NanoMagSat" satellites could then next be used as a baseline for the progressive establishment and maintenance of a permanent international network of a small number of satellites, operated and coordinated in a way analogous to the Intermagnet network of ground magnetic observatories.