A satellite encounters an aggressive environment (radiations , residual atmosphere , meteorites, etc.) causing transient disturbances (false control signals, background noise), instantaneous failures (electrostatic discharges, meteorite impacts, singular events ), and cumulative events with ultimate loss of functionality (erosion, contamination, degrading by radiations).

To reduce these risks, it is necessary to have a good knowledge of the environment and define rules for designing and selecting on-board equipment based on ground simulation and flight testing.