OBSERVATIONS OF CHARGING DYNAMICS

used to investigate the dynamics of natural charging events. Both eclipse and daylight charging events are considered, and typical responses illustrated by data from specific events. Two different physical processes are found to be involved in the charging process. One of these is straightforward: the spacecraft structure potential responds rapidly to changes in the environment, typically changing by hundreds of volts in a few seconds. The other process is more subtle: differential charging and potential barrier formation precede structural charging and determines the time scale, typically tens of minutes are required for the potential to change by several hundreds of volts. The latter process is found to be predominately responsible for daylight charging on both spacecraft