Discharge over spacecraft insulator surface in low earth orbit plasma environment

When a spacecraft operates at HV, the spacecraft body potential becomes hig hly negative with respect to the surrounding plasma. A laboratory experimen t has been carried out to study the interaction between the spacecraft insu lator surface and the plasma. Once a discharge occurs through the insulator at one point on the surface, the positive current to the circuit drives th e conductor, which lies below the insulator, positive. The potential of the undischarged surface increases as the conductor potential increases and co llects electrons by neutralizing the positive charge stored before the disc harge. The current path of an RC discharge is formed between the discharge spot and the undischarged insulator surface, which acts as the capacitance, through the plasma resistance and the spacecraft circuit resistance. An io n acoustic wave, launched by the potential jump of the undischarged surface , was detected by a Langmuir probe. There is a possibility that a very larg e amount of current flows into the spacecraft body circuit because the capa citance of the entire spacecraft surface is large.