As part of the European Union Framework 7 ACCORD (Alignment of Capability and Capacity for the Objective of Reducing Debris) project, concepts for an environmental impact rating system for the space environment have been devised, and details of a candidate prototype system are presented and discussed in this paper. The system aims to combine the capacity of mitigation measures to reduce the future debris population and the capability of industry to apply such measures. Using a holistic index of "health" of the space environment, the rating system subsequently produces a single score reflecting the impact of a candidate spacecraft on the environment. The system focuses on the state of the debris environment, the implementation of mitigation measures, and also takes into account the cost and technical difficulty associated with applying mitigation measures. The goal is to supply industry with a tool to evaluate how spacecraft design and operation can impact the long-term debris environment, and how improvements in environmental impact may be obtained through modification of these factors.