Space Shuttle Measurements Of The Galactic Cosmic Radiation Linear Energy Transfer Spectra Over A Solar Cycle And Their Comparison With Radiation Transport Model

A problem of considerable interest for radiation risk estimation of crew members on exploratory class missions is the accuracy of current models of the galactic cosmic radiation (GCR) environment and transport models. A systematic experimental evaluation of these models using data obtained from a tissue equivalent proportional counter (TEPC) flown on 15 Space Shuttle nights from April 1990 to February 1994, showed that the models predict, on average, absorbed dose and dose equivalent to +/- 10% of the observed values. There is, however, systematic underestimation of calculated dose as the level of solar modulation approaches the solar minimum. The observed fluxes are higher than the calculated fluxes by factors of 1.5-2.7, and suggest the need to improve the geomagnetic transmission functions.