The ESA M7 Plasma Observatory mission

The Magnetospheric System is the highly dynamic plasma environment where the strongest energization and energy transport occurs in near-Earth space.  Previous multi-point observations from missions such as ESA/Cluster and NASA/MMS have evidenced the fundamental role for these processes of cross-scales coupling . In the Magnetospheric System, the electromagnetic energy is converted into energized particles and energy is transported mainly at the ion and fluid scales. Simultaneous measurements at both large, fluid and small, kinetic scales are required to resolve scale coupling and ultimately fully understand plasma energization and energy transport processes. Here, we present the Plasma Observatory (PO) multi-scale mission concept tailored to study plasma energization and energy transport in the Earth's Magnetospheric System through with the first simultaneous in situ measurements at both fluid and ion scales. PO baseline mission includes one mothercraft (MSC) and six identical smallsat daughtercraft (DSC) in a two tetrahedra formation with MSC at the common vertex for both tetrahedra. PO baseline orbit is an HEO 8x17 RE orbit, covering all the key regions of the Magnetospheric System including the foreshock, the bow shock, the magnetosheath, the magnetopause, the transition region and the current sheet. Spacecraft separation ranges from fluid (5000 km) to ion (30 km) scales. The MSC payload provides a complete characterization of electromagnetic fields and particles in a single point with time resolution sufficient to resolve kinetic physics at sub-ion scales and fully characterize wave-particle interactions. The DSCs have identical payload, simpler than the MSC payload, yet giving a full characterization of the plasma at the ion and fluid scales and providing the context where energization and transport occurs. PO is the next logical step after Cluster and MMS and will allow us to resolve for the first time scale coupling in  the Earth's Magnetospheric System, leading to transformative advances in the field of space plasma physics. Plasma Observatory  is one of the three ESA M7 candidates, which have been selected in November 2023 for a competitive Phase A with a mission selection planned in 2026 and launch in 2037.