Several areas for improvement in the thermal and mechanical properties of the passive thermal control optical solar reflectors (OSRs) have been identified and discussed in a previous paper (1). These include the use of specialised optical coatings to optimise the emittance and absorptance of OSRs and also chemical treatments to provide greater resistance to handling and better conductivity where necessary. Each of the proposed techniques have been demonstrated and the most promising have been incorporated into development programmes leading to production. In parallel with this activity, examination of aspects of the whole passive thermal control system, in terms of optimal construction and assembly, and thermal and conductive properties is expected to commence shortly. It is anticipated that these will result in the specification and use of optimal thermal control systems for future satellites.