Probability Estimates of Solar Proton Doses During Periods of Low Sunspot Number for Short Duration Missions
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Abstract
In an earlier paper presented at ICES in 2015, we investigated solar particle event (SPE) radiation exposures (absorbed dose) to small, thinly-shielded spacecraft during a period when the monthly smoothed sunspot number (SSN) was less than 30. Although such months are generally considered “solar-quiet”, SPEs observed during these months even include Ground Level Events, the most energetic type of SPE. In this paper, we add to previous study those SPEs that occurred in 1973-2015 when the SSN was greater than 30 but less than 50. Based on the observable energy range of the solar protons, we classify the event as GLEs, sub-GLEs, and sub-sub-GLEs, all of which are potential contributors to the radiation hazard. We use the spectra of these events to construct a probabilistic model of the absorbed dose due to solar protons when SSN < 50 at various confidence levels for various depths of shielding and for various mission durations. We provide plots and tables of solar proton-induced absorbed dose as functions of confidence level, shielding thickness, and mission-duration that will be useful to system designers.
Description
NASA JSC
The Boeing Company
503
ICES503: Radiation Issues for Space Flight
Vienna, Austria
William Atwell, Retired Boeing Technical Fellow, Boeing Research & Technology, USA
Allan J. Tylka, Emeritus, NASA Goddard Spaceflight Center, USA
William F. Dietrich, Consultant, Prospect Heights, USA
Kristina Rojdev, NASA Johnson Space Center, USA
Courtney Matzkind, Boeing Research & Technology, USA
The 46th International Conference on Environmental Systems was held in Vienna, Austria, USA on 10 July 2016 through 14 July 2016.