An Overview of Spacecraft Charging Research in India: Spacecraft Plasma Interaction Experiments-SPIX-II

When a satellite leaves earth's atmosphere, the satellite potential floats negatively with respect to the surrounding plasma environment. Once the satellite surface consisting of different materials is charged and depending upon the dielectric constant of various materials, a potential difference develops between the surface of insulators and that of conductors, and under favorable conditions it exceeds the threshold value, which finally results in an electrostatic discharge (ESD). The potential difference arises on the solar panels when satellite bus voltage is increased to meet the present demand of the transponders. The resultant ESD may trigger a secondary arc, which can destroy the solar panel circuit and severely damage the substrate. Therefore, there is a need to test the performance of these solar arrays in a ground simulation facility. Recently, based on the collaborative research work in France, USA, and Japan, international standards for space solar panels have been finalized. This ISO document [ISO-11221] specifies qualification and characterization test methods to simulate plasma interaction and electrostatic discharges on solar array panels in the space. A linear circuit model has been jointly developed by Facilitation Center for Industrial Plasma Technologies, Institute for Plasma Research and ISAC, Indian Space Research Organization. This model explains the primary arc in low Earth orbit like plasma environment and geo-synchronous Earth orbit like electron irradiation environment. This paper discusses about the automated ISO test facility developed for detection and analysis of arc on the solar coupon. From the initial test results it has been confirmed that there is a gradual increase in surface potential on the solar coupon. The velocity of arc is measured based upon the neutralization currents in the adjacent solar cell strings. Damage caused by permanently sustained arc on solar coupon's surface is also studied.