LISA-T Part Four: Low Earth Orbit Testing of Thin-Film Solar Array Materials

Satellite miniaturization continues to create lower cost, faster paced, and higher risk tolerant options for space missions. While very capable, the size of these small spacecraft has restricted both advanced missions as well as small spacecraft traveling deeper into space. To improve technical and distance capabilities, more work (i.e. sensing, processing, communication, power generation, etc.) must be done from less resources (i.e. mass, volume, surface area, etc.). This is a particularly difficult challenge for power generation. To achieve higher power generation without significantly affecting spacecraft size, mass, and volume, traditional solar array concepts are being adapted to fully thin-film assemblies. Many of the thin-film materials that are used in these assemblies have been tested to simulated space environments on the ground, but little data exist for on-orbit performance and survivability. Herein, results from an in-space materials exposure experiment are detailed. This mission was conducted on the ‘Materials International Space Station Experiment Flight Facility’ and included copper indium gallium (di)selenide solar cells, inverted metamorphic multijunction solar cells, as well as various coatings thereof. Current-Voltage data taken both before and after the mission exposure are presented and compared to ground test results to elucidate degradation mechanisms and recommend development needs to extend the lifetime of these thin-film photovoltaic assemblies.