For state of the art cathodes for space applications, a stable operation during the entire life cycle has to be guaranteed. Therefore, at Thales, such devices are characterized thoroughly to assure the level of confidence regarding its long term behaviour. Since the introduction of the MM-type cathode, TED follows strictly a dedicated life test philosophy for space cathodes providing a considerable predictability of the relevant parameter evolution over life time, which consists of — among others — :• Parameter monitoring (e.g. Miram curve, work function…) • Accelerated life time diode testing (factor 60) • Life time modelling. Especially the thermally accelerated life testing allows a “compression” of the required 18.5 years in orbit life to a handsome on-ground test with less than 4 months duration. The comparison between such early laboratory results and the on-satellite tube behaviour (Fig.1) could be demonstrated for a significant number of satellites[1].