The Atypical Normal Potential Gradient Arcing on Solar Arrays

Most spacecraft arcing studies have been of the typical inverted gradient arcing, since geomagnetic substorms tend to charge spacecraft very negative of dielectric surfaces.  However, normal gradient arcing, where the... [ view full abstract ]

Most spacecraft arcing studies have been of the typical inverted gradient arcing, since geomagnetic substorms tend to charge spacecraft very negative of dielectric surfaces.  However, normal gradient arcing, where the spacecraft is positive of its dielectric surfaces, may be more damaging since it usually occurs at higher differential potentials, and thus may involve more capacitive energy.  Furthermore, there is evidence that some sustained arcs have started under normal potential gradients, and laboratory testing has shown that arcing can and does occur under normal gradient conditions.  Also, normal gradient arcing may occur on the backs of solar arrays, where diode banks are placed. Finally, normal gradient arcing may produce more contaminants and more radiofrequency interference than inverted gradient arcing, and thus may contribute to the GPS arcing problem.  In this paper we lay out the evidence for normal gradient arcing on orbit and in the laboratory, discuss differences in electron energy that may contribute to normal gradients, point out differences in test methods, comment on the arcing standards up to the present time and how they address normal gradient arcing, and lay out a plan of action against satellite anomalies that may result from normal gradient arcing.