Penetrating electron fluctuations associated with GEO spacecraft anomalies

Space weather is a known factor in spacecraft anomalies. Solar minimum carries with it an enhanced electron content, Electrons with sufficient energy to penetrate a spacecraft structure pose a hazard. They can accumulate in interior dielectrics creating an electric potential sufficient to cause a spontaneous breakdown. The resulting electrostatic discharge has been a cause of operational anomalies. The physical process by which the geosynchronous earth orbit (GEO) environment is populated by high-energy electrons is not fully understood. However, the solar-cycle, seasonal, and solar-rotational patterns observed are well documented. This paper reviews temporal fluence patterns and shows how some notorious satellite failures relate to them. It should be noted, however, the temporal response of a discharge is not necessarily at the instantaneous peak flux, but related to total local fluence and hom the dielectric responds to stress. Knowledge of the changes in mechanical and electrical properties of dielectrics in the space environment and a growing understanding of the variability of the electron population at GEO will enable the resolution of anomalies and facilitate their prevention.