Understanding optical changes in on-orbit spacecraft materials

Ground- and space-based optical observations of space objects rely on knowledge concerning how spacecraft materials interact with light. One common surface material for many currently active spacecraft is Kapton-HN (R) polyimide. Changes in optical signature for polymeric materials can occur due to surface degradation, leading to altered reflectivity, or due to radiation induced chemical modification, leading to an alteration of a material's absorption/transmission properties. The optical fingerprints of commonly used materials change continuously under exposure to high energy electrons, a primary damaging species in geostationary Earth orbit (GEO). Laboratory observations show that these changes in a material's optical signature are wavelength dependent and to some degree transient. This work investigates the changes in the optical reflection behavior of a variety of aerospace materials before and after electron irradiation. The results of this investigation will find use in the space debris remediation community for characterization of high area to mass ratio (HAMR) objects and other larger space debris.