Sunlight Illumination Models for Spacecraft Surface Charging

A model is developed to compute solar illumination of satellite components while accounting for multiple reflections, variable surface properties, and illumination source size. This model is implemented in OpenCL and integrated with the particle in cell satellite-environment simulation code, PTetra, enabling kinetic simulations in which photoelectron emission resulting from direct illumination and multiple reflections is taken into account. Simulation results obtained with a simple "toy geometry" are used to illustrate the effect of multiple reflections on the net current density at a satellite surface, and on the surrounding space charge potential. Results for the Solar Orbiter spacecraft show a small change in the overall charging and charge distribution around the solar wind analyzer instrument.