Evaluating Proton Dose Modeling in Shielded Systems With On-Orbit LED Degradation

Abstract

On-orbit output degradation of a light-emitting diode (LED) is used to compare displacement damage dose (DDD) calculation techniques, trapped proton environmental models, and increasing levels of shielding modeling fidelity to make conclusions on the margins inherent in dose modeling for light to heavily shielded systems. Good agreement with on-orbit degradation is found within a subset of the variety of these modeling techniques investigated. The fundamentals of the DDD calculations, both damage factors and their integration limits over varying energy ranges, are found to matter less than consideration of the secondary neutron contribution to the displacement damage in the more common heavily shielded systems uncovered with high-fidelity modeling codes. Historical minimum margins on top of trapped and solar radiation environmental models are confirmed to be outdated in comparison to the more recent use of confidence levels to address risk. Part-to-part and lot-to-lot part degradation variability is observed between the on-orbit data and identical modeling techniques. A quantitative evaluation of these modeling techniques and all the predicted data versus on-orbit data is presented.