Facets of spacecraft charging; critical temperature and dependence on ambient electron density

Spacecraft charging is important. Space plasmas, secondary and backscattered electrons, and surface conditions, are some of the main factors controlling spacecraft charging. At geosynchronous altitudes with Maxwellian space plasma, there are two properties for the onset of spacecraft charging. They are (1) existence of critical ambient electron temperature, and (2) independence of the ambient electron density. In space plasmas of Kappa or cut-off Maxwellian distributions, the two properties persist. In monopole-dipole configuration of dielectric spacecraft charging in sunlight, the high-level potential contours on the dark side wrap to the sunlit side and, as a result, the two properties also persist. However, the two properties do not apply to the following situations. They are charging by double-Maxwellian plasmas, charging by charged particle beam emissions, charging of plasma probes on spacecraft, low-level charging in the ionosphere, and low-level positive voltage charging of spacecraft in sunlight. We will summarize the various facets in a table, which, hopefully, will be very useful.