Computational method for analyzing the cumulative ionizing effect from solar-terrestrial charged particles and cosmic rays with geant4

A computational method for predicting and analyzing the cumulative effect of ionizing radiation in space is presented, taking into account the presence of the charged particles from the Sun and Earth together with the cosmic rays precipitating toward the vicinity of Earth. The method first integrates the population of charged particles along the trajectories of the instrument in space and then transports the charged particles across the shielding material. A novel method of interfacing a sophisticated mechanical design from computer-aided design (CAD) tools is introduced to geometrically model the shielding distribution of the orbiting instrument. The cumulative effect of ionizing radiation across the shielding distribution is then calculated based on the ray-tracing method and on a Monte Carlo simulation with Geant4. A description of this computational method is provided along with results for a representative example often encountered in the development of orbiting space instruments.