The PRETTY CubeSat’s secondary payload is a miniaturised dosimeter for space radiation, SATDOS, which will operate throughout its mission to give an authoritative map of low-Earth orbit. Its developer Seibersdorf Laboratories specialise in testing the rad-hardening of satellite components. SATDOS will measure various radiation influences on satellite systems, from transitory ‘single event effects’ to ‘total ionising dose’ effects that gradually undo overall system reliability.