Measurements of the radiation environment from CREDO-II on STRV and APEX

The Cosmic Radiation Environment and Dosimetry experiments (CREDO) have now been operational in complementary orbits onboard the Advanced Photovoltaics & Electronics Experiment Spacecraft and Space Technology Research Vehicle since the summer of 1994 enabling extensive comparisons of measured dose and linear energy transfer (LET) spectra with the standard environment models. Measurements have been made at a range of shielding depths and detailed spacecraft models are employed. Significant discrepancies are seen for the outer-belt electron component which shows large time variations. Shielding effects are shown to be highly significant for both dose and LET spectra. Even allowing for this the measured LET spectra are somewhat below the predictions for solar minimum.