Solar Cell Degradation Due to Proton Belt Enhancements During Electric Orbit Raising to GEO

The recent introduction of all-electric propulsion on geosynchronous satellites enables lower-cost access to space by replacing chemical propellant. However, the time period required to initially raise the satellite to geostationary orbit (GEO) is around 200 days. During this time the satellite can be exposed to dynamic increases in trapped flux, which are challenging to model. To understand the potential penalty of this new technique in terms of radiation exposure, the influence of several key parameters on solar cell degradation during the electric orbit raising period has been investigated. This is achieved by calculating the accumulation of nonionizing dose through time for a range of approaches. We demonstrate the changes in degradation caused by launching during a long-lived (hundreds of days) enhancement in megaelectron volt trapped proton flux for three different electric orbit raising scenarios and three different thicknesses of coverglass. Results show that launching in an active environment can increase solar cell degradation due to trapped protons by similar to 5% before start of service compared with a quiet environment. The crucial energy range for such enhancements in proton flux is 3-10 MeV (depending on shielding). Further changes of a few percent can occur between different trajectories, or when a 50-mu m change in coverglass thickness is applied.