Probabilistic Modeling of the Space Radiation Environment

The design of and planning for space missions must account for possible solar energetic particle (SEPs) events during these missions. Historically, missions account for SEPs by designing or planning to survive in the worst known operating environment. While this approach ensures that the satellite is protected against the worst environment on record, it usually leads to expensive over-design of the satellite. For this reason, it is important to choose a mission-specific design reference environment which will lead to the desired mission reliability while avoiding expensive over-design of the satellite.

We will describe two different probabilistic models for Solar Energetic Particle events. These models allow the user to tailor the design reference environment for his mission (characterized by its start date and duration) and to specify a confidence level for reliable mission operations which he wishes to achieve.

The first model is an episode-integrated fluence model. It is intended to estimate the highest dose that could be accumulated over periods ranging from a few weeks to several years. It is valid through 2053. The second model is a peak mission flux model. This model can be used for mission durations ranging from 10's of minutes to many years. It is also valid through 2053. It is used for estimating peak single event effect rates in satellite electronics. Both models use the probabilistic modeling techniques developed by Xapsos et al. (1998). For short missions (10s of minutes), the peak flux model uses a new data driven approach to create the reference environment. For longer missions it follows the method of Xapsos, making use of an extended database.

Xapsos, M. A., Summers, G. P. and Burke, E. A. (1998) 'Probability model for peak fluxes of solar proton events', IEEE Transactions on Nuclear Science, 45(6 PART 1), pp. 2948-2953. doi: 10.1109/23.736551.

DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited.

Approved for Public Release

18-MDA-9478 (22 Jan 18)