Assessment of deep dielectric discharging in spacecraft

Summary form only given. Charging of spacecraft by magnetospheric plasma can produce discharging, which is one possible cause of anomalous operation. On communications satellites in geosynchronous orbit, the discharge-induced anomalies divide into two categories: those possibly caused by surface charging, in medium-energy plasma clouds in the midnight-to-dawn sector, and those caused by deep dielectric discharging by high energy electrons, which can generally be more harmful and are evenly distributed around the geosynchronous arc and either correlated or anticorrelated with the cycle of equinoxes. Current-generation technology allows for prevention of surface discharging by the use of conductive coatings on all spacecraft surfaces. Mitigation of deep charging effects is an underdeveloped area of technology. The authors have difficulty even understanding the phenomenology of destructive internal discharging. To further this understanding, some promising methods of instrumentation have been suggested, to detect either surface or deep dielectric charging. These sensors will gather in-flight data to identify at-risk components and systems and to determine whether the commonly employed preventive methods (shielding, grounding or exposed metal) are effective in operation. The types of sensors are reviewed and some existing results are interpreted. For on-orbit satellites it may be possible to discriminate between deep dielectric discharging effects and surface discharging effects by combining the results of the two types of sensors with time of year and orbital position.