Abstract
In preparation for deployment of the Galileo satellite navigation system, Europe has launched a test satellite, Giove-A. One of its objectives is to measure the radiation environment encountered in medium Earth orbit (MEO) which is a new regime for European missions. Giove-A therefore includes two radiation environment monitors: Merlin supplied by QinetiQ and CEDEX supplied by the University of Surrey. Merlin measures electrostatic charging and electron fluxes, total ionising dose, energetic proton fluxes and heavy ion linear energy transfer (LET) spectra. CEDEX monitors energetic proton fluxes, heavy ion linear energy transfer (LET) spectra and ionising dose rates. Giove-A, which was built by SSTL (UK), was successfully launched on 28th December 2005 into a 23,600 km circular, 56 degree inclination orbit. Data received since launch has been analysed and demonstrates that the MEO environment is highly dynamic due to the influence of space weather. Numerous electron belt enhancement events have been observed and the charging effects of these events been characterised. Total ionising dose is also seen to be delivered almost wholly during electron events.