The phenomenon of surface charging leads to requirements to control the electrical behaviour of materials directly in contact with the ambient plasma. These materials can become the source of electrostatic discharges whose principal hazardous effect is to cause damage to electronic systems elsewhere on the spacecraft and of undesired electric fields, whose principal effect is to interfere with measurements of the ambient medium. The components affected include any spacecraft material on the outer surface of the spacecraft, e.g. thermal blankets, solar cell cover glass, sensor optics, exposed cables.
In addition, thin films, e.g. thermal blankets, sometimes do not shield underlying materials from the electrons mainly responsible for high level surface charging (~ 10 keV to 50 keV). Hence components affected include any spacecraft material covered by only a thin film, with thickness equivalent to less than 100 micro-meters Aluminium (0,03 g/cm2), including multi-layer insulation. The requirements in this clause also apply to surfaces partly exposed to space through small apertures (e.g., venting holes), although holes can be designed so as to avoid direct exposure.
Another factor influencing charging levels is the conduction path from each surface to ground and to other parts on the spacecraft. Hence these requirements cover all components concerned with the grounding and electrical continuity of the spacecraft structure, subsystems and electronics.
In addition to considering components that affect the build-up of charge, the effects of any resulting electrostatic discharges, i.e. coupling to sensitive devices, are controlled in order to prevent discharges causing damage and interference to systems elsewhere. This is an EMC issue that is common to electrical transients, however generated. Because this is part of general EMC design, specific requirements are not included here but standard EMC procedures are applied to control the transmission of transients.
These requirements also cover solar arrays and there are additional specific requirements for these due to the possibility of secondary discharges, fed by the power of the array itself, in clause 7.