Numerical Simulation of SMART-1 Hall-Thruster Plasma Interactions

Abstract

SMART-1 has been the first European mission using a Hall thruster to reach the moon. An onboard plasma diagnostic package allowed a detailed characterization of the thruster exhaust plasma and its interactions with the spacecraft. Analysis of in-flight data revealed, amongst others, an unpredicted large cyclic variation of the spacecraft floating potential and a mysterious asymmetry in the plasma surrounding the spacecraft. To investigate the details of the anomalies, we developed the numerical software tool SmartPIC to characterize and predict spacecraft-plasma interactions. Technical details, such as solar arrays and onboard diagnostic devices, have been modeled with high accuracy. All basic plasma parameters, the spacecraft floating potential, backflow distributions, and ion impact energies are calculated by the code and are available in high spatial resolution throughout the computational domain containing the entire satellite. It was possible to clearly identify the rotating solar cells arrays as the source of the cyclic variation of the spacecraft floating potential. Furthermore, the asymmetry of the plasma formation around the spacecraft is linked to the location of the neutralizer causing a region of increased charge-exchange collisions particle generation. Both of these results have significant impact on the implementation of electric propulsion systems on satellites.