The influence of capacitor effects on the surface potential of satellites with partially insulating surfaces in the solar wind

A simple model is presented for the estimation of the surface potential of satellites with insulating coating. Any small area F of the surface is represented by a capacitor, which is charged up by the plasma and photoelectron currents. Using simple approximations for the currents, the surface potential is calculated for plasma parameters supposed to describe the solar wind between 0.3 a.u. and 1 a.u. distance from the Sun. The potential of the shaded side of the satellite is found to depend strongly on the capacitance of the surface. High capacitances or high spin frequency for the spacecraft can be used to limit the potential differences on the surface. In any case the angular surface potential distribution is asymmetric with respect to the solar wind velocity.