Implications for space radiation environment models from CREAM & CREDO measurements over half a solar cycle

Flight data obtained between 1990 and 1997 from the Cosmic Radiation Enviro nment Monitors CREAM & CREDO carried on UoSAT-3, Space Shuttle, STRV-1a (Sp ace Technology Research Vehicle) and APEX (Advanced Photovoltaic and Electr onics Experiment Spacecraft) provide coverage over half a solar cycle. The modulation of cosmic rays and evolution of the South Atlantic Anomaly are o bserved, the former comprising a factor of three increase at high latitudes and the latter a general increase accompanied by a north-westward drift. C omparison of particle fluxes and linear energy transfer (LET) spectra is ma de with improved environment & radiation transport calculations which accou nt for shield distributions and secondary particles. While there is an enco uraging convergence between predictions and observations, significant impro vements are still required, particularly in the treatment of locally produc ed secondary particles. Solar-particle events during this time period have LET spectra significantly below the October 1989 event which has been propo sed as a worst case model.. Crown Copyright (C) 1999 Published by Elsevier Science Ltd. All rights reserved.