The European GNSS system Galileo is being designed to operate 30 satellites in MEO. The design of these satellites requires a thorough understanding of the radiation environment. To this end a pair of radiation monitors, CEDEX and Merlin, were carried on the precursor mission GIOVE-A. These collected data on electrons, protons and heavy ions over the nominal mission life of 27 months. This work was aimed at understanding the response of the instruments and therefore understanding the radiation environment in MEO to determine if existing models of the environment are accurate enough for the design of the Ml Galileo constellation.