A New Charging Model for Spacecraft Exposed Dielectric (SICCE)

The exposed dielectrics outside a spacecraft interact directly with the ambient plasma. Moreover, they are exposed to the energetic charged particle radiation. The low-energy plasma and the energetic radiation are both important factors for the dielectric charging. Tailored to this special condition, a model named surface and internal coupling charging model for exposed dielectric is newly proposed. It is based on the current conservation law regarding the charging potential as the unknown variable. All the three kinds of currents, namely the surface incident current, internal deposition current, and the leakage current, are considered. Among them, the leakage current is the most complicated, which is determined by the potential and the dielectric conductivity affected by the electric field, radiation dose rate, and temperature. The determinate solution of the model is analyzed and a numerical solution in 1-D case is provided using an iterative algorithm. The solution includes the potential of spacecraft body, distribution of dielectric potential, and electric field. If the internal deposition current is equal to zero, the new model degenerates into the one depicting the surface charging. A simulation is carried out to a polyimide dielectric board considering the typical environment of GEO orbit. The surface charging potential is verified by comparing with the online tool by ESA for surface charging. The internal charge deposition is found to have little effect on the surface charging potential, but it can result in electric field distortion, which is of significance for the dielectric breakdown discharge. Therefore, the new model can provide a more comprehensive assessment for the spacecraft exposed dielectric charging.