Thermal design for high-temperature high-irradiance testing of space solar panel components

Emcore has been performing High Intensity High Temperature (HIHT) tests on covered, interconnected cell (CIC) assemblies. End-of-life performance of spacecraft solar panels depends to a great extent on changes in the optical properties of the CICs´ coverglass adhesive during the mission. An important change in silicone coverglass adhesives is observed as degradation of short wavelength transmission, often called “darkening” or “yellowing”. This is understood to be driven by exposure to high intensity UV and by exposure to elevated temperature. Solar panels on the Solar Probe Plus (SPP) spacecraft will be exposed to both high UV irradiance and elevated temperature over the course of a long mission. This paper reports on the thermal-mechanical design work performed and planned by Emcore in order to test CICs designed for SPP under these extreme conditions. Three types of thermal test designs are presented: conduction/convection with a single fixed temperature, thermal radiation with multiple fixed temperatures, and thermal radiation with a variable single temperature. We present some detail from predictive thermal models used in the test designs along with temperature data measured during the test runs.