Scientific spacecraft, which have the measurement of ambient electric field or of low energy particles as part of their mission, have more stringent requirements in terms of differential charging, absolute spacecraft potentials and contamination by spacecraft generated particles. For this reason, clause 6.7 provides specific requirements for this case.
Since quantitative requirements are often mission specific, the requirements in clause 6.7 are not intended to be exhaustive, but to cover the common aspects that can be expected in most of the scientific missions.