The Worst Case GEO Environment and the Frequency of Arcs in GEO

Proper spacecraft design and testing depend on a knowledge of the worst case environment and the number of arcs to be endured during the spacecraft lifetime. In this paper, we define the criteria to be used to specify the worst case geosynchronous earth orbit (GEO) charging environment (plasma density and temperature), including the physical constraints on particle and magnetic field energy densities and the relative importance of frame charging and differential charging. A previous estimate of the frequency of arcing (found in the literature and incorporated into an International Standards Organization standard) and the consequent total number of arcs to be encountered in a GEO satellite lifetime are found to be incorrect because they were based on environmental measurements using a faulty algorithm to determine spacecraft charging and plasma density. Using more accurate estimates of the frequency of GEO plasma densities and temperatures, we arrive at a much lower estimate of the total number of arcs during a GEO satellite lifetime. Finally, the worst case GEO charging environment seen to date is determined from Nascap-2k simulations. Our estimates of worst case charging environments and arc frequencies may be more confidently used by GEO spacecraft designers and test engineers.