4.1.2 Most common engineering concerns

The following are the most common engineering concerns related to electrical charging of a spacecraft:

• Surface charging due to charge accumulation on spacecraft surface is a potential cause of spacecraft anomalies. High levels of differential potential may lead to ESDs which may couple to spacecraft electronics and damage electronic components. Initial ESDs may also trigger the generation of secondary arcs on high voltage systems. Several occurrences of permanent solar array power loss in space are believed to be related to such phenomena.

• Internal charging due to penetrating electrons is another cause of spacecraft anomalies. ESDs may be generated within the spacecraft Faraday cage and in close proximity to vulnerable components.

• Current leakage affects exposed high voltage systems which can experience significant power loss due to current leakage sustained by freely moving particles (from the plasma or photo-electrons).

• Environment modification occurs as a bi-product of surface charging and/or particle emission by surfaces. Electric charge and plasma density are affected in a volume that can extend very far from the spacecraft (many times its typical dimension). This is usually a critical problem for scientific plasma measurements that cannot retrieve the natural parameters to be measured without taking these alterations into account.

• Electric propulsion actively modifies the local environment and creates a local plasma population and modifies the current balance of the satellite that otherwise can occur. It can affect other spacecraft systems, e.g. by increased contamination.

• Electrostatic tethers make use of current collection from the ambient medium to allow a current to pass. These also change the currents passing through the system and can lead to high potentials.

Table 4‑1 contains a more complete list of the various effects in which space plasma plays an important role.

A quantitative description of the most important processes in spacecraft-plasma interactions is given in Annex C but a brief qualitative overview follows here.