Ground testing of an on-orbit atomic oxygen flux and ionizing radiation dose sensor based on material degradation by the space environment

Atomic oxygen is the predominant neutral species in the low Earth orbit environment and is considered to be one of the main hazards to spacecraft materials. The pursuit nowadays of satellite projects toward very low Earth orbit missions, results in exposure of these spacecraft to extremely high atomic oxygen flux. In geosynchronous Earth orbit spacecraft are exposed to charged particles and ionizing radiation which may affect their electronics. Therefore, obtaining accurate on-orbit atomic oxygen flux and total ionizing dose data will contribute to the design of the next generation of spacecraft by facilitating reliable prediction of material and electronics durability for a specific mission. Atomic oxygen flux and ionizing radiation can be measured by a variety of techniques which are either extremely expensive, require retrieval of samples, or difficult to implement on board small spacecraft. In this study, we present validation test results of the on-orbit materials degradation detector, in a series of ground-based measurements. The on-orbit materials degradation detector is based on photovoltaic cells and can measure real-time space environment components. The goal of this study is to validate the on-orbit materials degradation detector's accuracy during atomic oxygen flux measurements under severe conditions and to calibrate it for total ionizing dose measurements. The validation of the on-orbit materials degradation detector is a step toward its integration with the THERME experiment, which was developed in order to provide real-time ageing measurements of thermal control coatings. The combined THERME - on-orbit materials degradation detector will allow correlation between real-time space environment effects and ageing of materials. The results show the versatility of the on-orbit materials degradation detector, i.e. its ability to measure real-time and accurate atomic oxygen fluxes while being exposed to extreme thermal cycles, its ability for total ionizing dose measurements, as well as its real-time material degradation detection capability.