Approximately half of EISCAT operations are devoted to Special Programmes. These are experiments carried out by individual scientists or collaborating groups, usually in connection with highly specialised research topics. Data from Special Programmes are reserved for the proposing experimenters for the first year after the data have been taken. Thereafter, their status becomes the same as Common Programme data. Because Special Programmes are intended for the specialised study of certain events or phenomena, the experiments tend to comprise non-standard modes, different from the normal Common Programmes, though this is not always the case.