Assessment of Spacecraft Internal Charging in the Earth's Outer Radiation Belt

The internal charging effects triggered by energetic (>100 keV) electrons in the Earth's radiation belts can cause anomalies and failures of electronic components aboard spacecraft. Given the critical importance of safeguarding space assets, it is essential to estimate internal charging risks, which depend highly on the distribution of radiation belt electron fluxes. In this study, we reconstruct the distribution of electron fluxes using a 3-D data assimilative model, which integrates a radiation belt numerical model with multi-satellite observations using the Ensemble Kalman Filter. We then estimate the spatial and temporal evolution of internal charging currents and risks across the entire outer radiation belt under specific shielding/dielectric layers and configurations. Furthermore, we analyze the impacts of shielding thickness on charging currents for different characteristic energy spectra. Our results reveal that for both power-law and exponential energy spectra, the charging current decreases monotonically with increasing shielding thickness. However, there exists a “critical shielding thickness” for the bump-on-tail (BOT) energy spectrum. Below this critical value, the charging current increases with shielding thickness, whereas beyond it the current decreases. For the BOT energy spectrum, both higher electron energies corresponding to peak flux and thinner dielectric thicknesses can result in an increase in the “critical shielding thickness.” Our results shed important light on the prediction of satellite internal charging risk under the exposure to Earth's highly dynamic outer radiation belt.