An Update of Spacecraft Charging Research in India: Spacecraft Plasma Interaction Experiments—SPIX–II

Arcing on spacecraft solar panels has been a major challenge since it was first observed in late 1970s. Scientists of leading scientific countries like USA, Japan, France, and others are working hard to understand various aspects of this charging-arcing phenomenon. Based upon the experimental simulation results, a few arc mitigation techniques have been developed. In 2003, the Indian Space Research Organization (ISRO) realized the necessity to develop an experimental setup for understanding the charging-arcing phenomenon on satellite's solar panels when parked in lower earth orbit (LEO) in the Space Plasma Interaction Experiments (SPIX) facility. The SPIX facility was jointly developed as a collaborative research project between the ISRO and the Institute for Plasma Research. In 2010, an initiative was taken for the upgradation of the SPIX facility for testing both LEO and geosynchronous earth orbit (GEO) satellite's solar panels by the following standard ISO 11221 experimental procedure and indigenously developed high-speed data acquisition and analysis system. Various types of solar panel coupons were tested in upgraded SPIX-II facility. Sample solar panel coupons used in the experiments can be categorized based on the types of solar cells and the configurations of solar cell that includes different interstring gaps and grouting. For LEO satellite coupons, depending upon the types of solar panel coupons, different bias voltages were applied and threshold voltage was determined. Threshold arc tests were done at different bias voltages and electron gun energies for GEO satellite's coupons. Arc rates and threshold voltages were measured for each type of solar panel coupon, which determined their durability and reliability in harsh environmental conditions. Grouted solar panel coupons had higher threshold voltage in both LEO and GEO worst environmental conditions. Results showed good repeatability and reproducibility for both LEO and GEO experiments. To measure sustained arc conditions, experiments were performed with different string voltages and string currents in both LEO and GEO environmental conditions. It was experimentally validated that the probability of temporary sustained arc or permanently sustained arc increases on increasing either string voltage or string current. In addition, an attempt is also made to understand the role of plasma curing of solar panel coupons and its impact on arc mitigation for GEO environment like space conditions.