Spectrometers Results of Material Exposure and Degradation Experiment Onboard International Space Station

Material Exposure and Degradation Experiment is an active material experiment exposed to the low-Earth-orbit environment for 18 months onboard ISS/Columbus. This paper focuses on the results of Spectrometer experiment, one of the seven subunits of MEDET. The purpose of this experiment is to measure in real time thermooptical properties of a large set of materials designed for space applications (20 different materials). Some of these materials have been developed for atomic oxygen-resistant protection for low-Earth-orbit spacecraft applications. The evolution of their thermooptical properties on the International Space Station orbit allows for monitoring the degradation of materials mainly due to ultraviolet and atomic oxygen before recovery phenomena take place at the time the experiment returns into the atmosphere. Ultraviolet-visible transmission spectra from preliminary flight data highlight the two degradation phenomena expected for such a mission, namely: yellowing for atomic oxygen protected polymeric films and silicone resins due to ultraviolet exposure, and the decrease of thicknesses for other samples like polymeric films due to atomic oxygen erosion.