Radiation environments and effects must always be considered early in the mission design cycle. Energetic charged particles, which can penetrate outer surfaces of spacecraft (for electrons, this is typically above 100 keV, while for protons and other ions this is above 1 MeV), will be encountered throughout the mission lifetime and the effects on the different components have to be considered. Neutrons, gamma-rays and X-rays are also considered energetic particles in this context.