OMEP-EOR: A MeV proton flux specification model for Electric Orbit Raising missions

Abstract

Electric Orbit Raising (EOR) for telecommunication satellites has allowed significant reduction in on-board fuel mass, at the price of extended transfer durations. These relatively long transfers, which usually span a few months, cross large spans of the radiation belts, resulting in significant exposure of the spacecraft to space radiations. Since they are not very populated, the radiation environment of intermediate regions of the radiation belts is less constrained than on popular orbits such as LEO or GEO on standard environment models. In particular, there is a need for more specific models for the MeV energy range proton fluxes, responsible for solar arrays degradations, and hence critical for EOR missions. As part of the ESA ARTES program, ONERA has developed a specification model of proton fluxes dedicated for EOR missions. This model is able to estimate the average proton fluxes between 60 keV and 20MeV on arbitrary trajectories on the typical durations of EOR transfers. A global statistical model of the radiation belts was extracted from the Van Allen Probes (RBSP) RBSPICE data. For regions with no or low sampling, simulation results from the Salammbô radiation belt model were used. A special care was taken to model the temporal dynamics of the belts on the considered mission durations. A Gaussian Process (GP) model was developed, allowing to compute analytically the distribution of the average fluxes on arbitrary mission durations. Satellites trajectories can be flown in the resulting global distribution, yielding the proton flux spectrum distribution as seen by the spacecraft. We show results of the model on a typical EOR trajectory. The obtained fluxes are compared to the standard AP8 model, the AP9 model, and validated using the THEMIS satellites data.We illustrate the expected e ect on solar cell degradation, where our model is showing an increase of up to 20% degradation prediction compared to AP8.