A GIOVE Derived Galileo Electron Spectrum and Comparison to Models

Two precursor satellites for the European satellite navigation system, Galileo have been launched, GIOVE-A and -B. Both spacecraft carry monitors to characterise the radiation environment in the MEO environment. CEDEX, built by the University of Surrey and Merlin, built by QinetiQ, are carried on GIOVE-A and SREM built by Oerlikon Space is on board GIOVE-B. All three monitors have been operating since their respective launches and have measured the trapped electron population as well as solar protons and GCRs. An electron energy spectrum has been derived from Merlin measurements and validated with data from GIOVE-B/SREM and the IREM instrument on the INTEGRAL observatory. The derived energy spectra are compared to environment models, suggesting a harder energy spectrum than expected, but not exceeding worst-case FLUMIC predictions.