While various layer schemes have been developed to protect thin film silver mirrors from tarnish and corrosion, the mechanisms by which these protective layers improve mirror durability are not fully understood. Mixed flowing gas exposure of plasma beam sputtered silver mirrors was used to investigate how the composition of the very thin adhesion layer changes the mechanism of corrosion feature growth. Two model mirror coatings were analyzed in which the composition of the base layer below the silver and the adhesion layer above were varied. Optical measurements and microscopy, SEM, TEM, and EDS were used to characterize the compositional and chemical effects at the layer interfaces. Large circular corrosion features formed along the silver-chromium interfaces; the addition of nickel to the layers on either side of the silver limited the growth of these features, but resulted in the corrosive attack of the silver itself.
Molecular contamination degrades sensitive spacecraft surfaces and can adversely affect the useful life of a spacecraft.
In order to accurately predict spacecraft performance and end of life, an understanding of the primary mechanisms and
processes involved in the deposition and "fixing" of molecular contaminants is necessary. The objective for this research
effort has been to investigate how solar vacuum ultraviolet (VUV) radiation and surface temperature influence
photochemical reactions of molecular contaminants. This report presents the effects of VUV intensity and surface
temperature on photo-deposition and "photo-fixing" of dioctyl phthalate (DOP) films.
The use of digital cameras and digital imaging software for the measurement of particle obscuration is discussed. Novel
calibration standards are used to evaluate the sensitivity and accuracy of commercially available digital cameras for
detecting microscopic dust particles and other contaminant features on surfaces. Lighting and illumination effects are
also illustrated and discussed. The digital image histogram of particles on a surface is shown to give good results for the
percent area coverage.