Comparison of CREME Model LET Spectra with Spaceflight Dosimetry Data

Galactic cosmic radiation (GCR) is an important component of the radiation dose to astronauts when Earth´s magnetic shielding is low, for example, on spaceflights outside the magnetosphere and in high inclination orbits. In high inclination orbits, low energy (high LET) particles are transmitted through the field only at extreme latitudes, but can dominate the orbit-averaged dose. We have compiled existing measurements of heavy ion (HZE) doses where GCR is expected to be important: Apollo 16 and 17, Skylab, Apollo-Soyuz Test Project. The LET spectra, due to direct ionization from GCR and its nuclear fragments, for each of these missions has been estimated based on the NRL CREME environmental model and particle transport codes developed by us. The resulting comparisons validate the CREME model predictions of high-LET galactic cosmic ray fluxes to within a factor of two or three. Some systematic differences between model and data are identified.