The Timescale of Surface-Charging Events

The timescale for creating high potentials on shadowed spacecraft surfaces depends on the conductivity of the surface in question, whether the neighboring surfaces are tied to the spacecraft frame or not, and on the space environment input. It is understood from laboratory and spaceflight measurements that the likelihood of a large surface potential and the timescale over which it might occur depends on these variables, yet the complex interplay between them makes the hazard difficult to assess even in controlled experiments. In this paper, we approach the specific question of the timescale of surface charging using several data sets in several orbit regimes: geostationary orbit (GEO), highly elliptical orbit (HEO), and low-Earth orbit (LEO). The measurements that we will show involve different approaches to the question of surface charging and subsequent electrostatic discharge (ESD) (GEO: surface charge monitors; HEO: direct plasma measurements; LEO: anomalies due to surface charging). However, the main strengths of the data are derived from their long duration covering multiple years and their occasional overlap in time. Here, we report on the timescale of surface-charging events at different locations in the magnetosphere across ~11 years of geomagnetic activity. The results will be relevant for assessments of space system impacts due to surface discharges and ESD, simulations of surface charging, and laboratory testing of flight system designs.