Preliminary analyses of Surface Charging effects for the Plasma Observatory (PMO) mission

Plasma Observatory (PMO) 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 June 2026 and launch in 2037. PO scientific theme is unveiling plasma energization and energy transport in the near-Earth plasma environment through multiscale observations. The baseline mission includes seven identical smallsat Sister Space Craft (SSC) embarking state of the art instruments for electromagnetic fields and particle measurements. This work presents the results of preliminary surface charging analyses performed for the PMO.

Surface charging phenomenon is induced by the interaction of the spacecraft with the surrounding plasma environment and can lead to several potentially harmful consequences, including interference with ground communications, on-board electronics and scientific instruments. Since PMO aims to investigate the plasma properties in the near-Earth environment with high precision, any perturbation to the instruments generated by surface charging represents a concern for science return. Moreover, the charging phenomenon can lead to the development of variable electric and magnetic fields and, in most extreme scenarios, the onset of electrostatic discharges that may cause temporary malfunctions or, in worst cases, mission loss. These discharges occur when the potential difference between near surfaces, exceeds a critical threshold. Such conditions are more likely to occur when the spacecraft structure includes both conductive and dielectric materials. For PMO this risk is expected to remain low, as per baseline the seven spacecrafts will be predominantly conductive, allowing fast charge redistribution. However, as the PMO spacecraft will traverse multiple plasma regions of the Earth’s magnetospheric system during the Key Science Phases (KSPs), evaluating the resulting charging effects is essential. These analyses are crucial not only for PMO but for all space missions, as they support the development of reliable spacecraft designs and ensure safe operation in diverse plasma conditions.