Analytical Method for Predicting Spacecraft Power Generation on Partially Shaded Solar Panels

Telecommunication satellites in Earth geostationary orbit (GEO) often have large communication antennas and other external appendages. Throughout the 24-hour day in GEO orbit, and depending on the orbit seasons, the external appendages may cast various changing shadows onto the satellite's solar arrays. The geometry and composition of the external appendages result in a complex shadowing profile involving soft and hard shadows. These conditions have a nontrivial impact on the solar array power generation and the spacecraft payload power management. Space Systems Loral (SSL) has developed an analytical tool to accurately predict the changes to array power using a combination of CAD modeling, raytracing and simulation of solar cell performance under various levels of illumination. The predictions from the analytical tool have been shown to correlate well with on-orbit solar array telemetry; in particular, shadow correlation data from a 12-m unfurlable mesh antenna will be presented.