Transient Analysis of Spacecraft Exposed Dielectric Charging Using SICCE

Spacecraft exposed dielectric interacts directly with the ambient plasma and may be faced with energetic electron irradiation. Using the charging model surface and internal coupling charging model for spacecraft exposed dielectric (SICCE), it is possible to investigate this special charging process, including both surface charging (SC) and deep dielectric charging. Based on the finite-difference time-domain method, a transient solution of the SICCE in the 1-D case is proposed in this paper with adequate verifications. An important improvement is made to the SICCE by employing secondary electron yield formula in Katz form, which is the same with Spacecraft Plasma Interaction Software (SPIS) and NASA Charging Analyzer Program (NASCAP)-2k. The typical charging environment for exposed dielectric is assumed Geosynchronous Earth Orbit (GEO) worst plasma environment combined with Flumic3 energetic electron irradiation. The charging characteristics of a 3-mm polyimide board with front surface exposed to this typical environment and back surface connected to the spacecraft body is investigated. The total charging process in time-domain can be divided into three stages: the first is dominated by fast SC of spacecraft body with the typical time less than 1 s determined by spacecraft capacitance, the following stage lasts until the dielectric surface potential reaches equilibrium with the charging time of several hundred seconds determined by dielectric board capacitance, and the deep dielectric charging dominates in the third part with the charging time more than 2 h. If the magnitude of the body potential is larger than the dielectric surface potential in equilibrium, overcharge and feedback appear in the surface potential evolution. Peak electric field appears on the point connecting spacecraft body and reaches a maximum value in charging equilibrium. In the case of multiple roots of SC equation, transient solution has the advantage of avoiding unstable charging potential. This investigation can further enrich engineers' understanding of spacecraft exposed dielectric charging.