The Themis project is a NASA mission, initially involving 5 satellites (2 of which have now been repurposed to carry out the organisation’s Artemis mission in lunar orbit). Themis instruments were designed by American scientists in collaboration with French laboratories.
Themis’s main objective was to determine precisely the nature and location of the macroscopic process (current interruption or magnetic reconnection) responsible for substorms, to study its cause-and-effect relationships, and describe its spread and interactions. With the help of ground assets, another objective was to study the ionosphere/magnetosphere interactions. Secondary objectives were focused on the study of radiation belts, the magnetopause and boundary layers.
Each Themis satellite is equipped with these 5 instruments:
- FGM (FluxGate Magnetometer)
- EFI (Electric Field Instruments)
- ESA (ElectroStatic Analyzer)
- SCM (Search Coil Magnetometer)
- SST (Solid State Telescopes)
2 French laboratories took part in this mission: the LPP (plasma physics laboratory, former CETP) and IRAP (astrophysics and planetology research institute, former CESR). The LPP provided magnetic aerials and triple-axis structures (build by GDTech). The preamplifiers were manufactured in France (by 3D+). The LPP also handled mission parameters definition, technical maintenance, planning, and support-integration for the preamplifiers, contributed to the integration steps, and provided a sniffer to measure electromagnetic pollution from other experiments and satellite systems. IRAP took part in defining the mission objectives and parameters and is involved in data analysis and interpretation.