Apparatus to measure the reflectivity of silver and rhodium mirrors at elevated temperatures [space power solar concentrators]

Solar thermal power and propulsion systems are being considered for spacecraft where sunlight is directed into the aperture of a heat receiver by first reflecting the sunlight off a large primary concentrator and then passing it through a much smaller secondary concentrator. Selection of materials and coatings for secondary concentrators is of importance owing to the high energy throughput of such optical systems. This paper addresses an apparatus to measure the reflectivity of mirror materials at the elevated temperatures expected for secondary concentrator applications.