Calculating Ionizing Doses in Geosynchronous Orbit from In-situ Particle Measurements and Models

Long-term electron and proton in-situ measurements made by Los Alamos National Laboratory Geosynchronous (GEO) satellites are used to calculate total ionization dose (TID) values and daily/yearly dose rate (DR) values in GEO orbit caused by the natural space environment, and these TID and DR values are compared to those calculated from empirical radiation models. Results over the solar cycle 24 show that, for the solid sphere geometry with 100 mil Al shielding, electron TID from measurements in LANL-04A GEO orbit is about half of the values calculated from AE8 and AE9 models, while the TID on another GEO satellite 1994-084 is two times lower. Also, it is shown that even the few solar energetic proton events contribute significantly to the proton TID. Factors affecting those dose calculations are discussed. Results from this study provide out-of-sample tests on the reliability of empirical space radiation models and help estimate the margin factors of calculated ionization dose values in GEO orbit.