Development of a Phosphor-Based Sensor Suite for Spacecraft Health Monitoring

Abstract

The current interest in returning to the Moon and Mars by 2030 makes cost effective and low mass health monitoring sensors essential for spacecraft development. In space, there are many surface measurements that are required to monitor the condition of the spacecraft including: surface temperature, radiation fluence, and impact. Through the use of phosphors, materials doped with trace elements that give off visible light when excited, these conditions can be monitored. Practical space-based phosphor sensors will depend heavily upon research investigating the resistance of phosphors to ionizing radiation and the ability to anneal or self-heal from damage caused by ionizing radiation. Preliminary investigations into these sensors have recently been performed using ZnS:Mn. This phosphor has been found to be temperature sensitive from 100 to 350 C and responsive to both impact and radiation fluence. A 3 MeV proton fluence as small as 2.28 x 10 mm was found to statistically reduce the ZnS:Mn fluorescence decay time for temperatures less than 200 °C. Reductions in decay time appear to be proportional to increasing fluence. This testing has also shown that the proton damage decreases the light emission with respect to impact energy. While this testing is not all inclusive; it does illuminate the process that can be used in the selection of appropriate sensor materials.