Development of circuit model for spacecraft charging studies

The external surfaces of a spacecraft exposed to Earth's magnetospheric plasma can build up differential voltages which can result in an electrostatic discharge (ESD). This discharge may induce transient electromagnetic interference (EMI) in the electronics circuitry and may give rise to switching anomalies or system failure under certain environmental conditions. This paper outlines the development of circuit model of a spacecraft for surface charging studies by assuming Maxwellian distribution function to represent the plasma particles in space. Analytical expressions for charging and discharging current sources of the geosynchronous Earth orbit (GEO) plasma have been obtained. A numerical solution procedure using method of moments and triangular patch modelling to determine the capacitance of conducting objects in free space has been developed. Differential equations of spacecraft charging have been derived and the surface charging of INSAT-2E spacecraft has been simulated.