VEM/VenSpec-M Coating Degradation Study and Thermal Performance Investigation

Abstract

Optical instruments on space missions are exposed to the harsh environmental conditions of space. In addition to these influences, the target planet also significantly determines these environmental influences. These environmental conditions must be considered in the design of a sensitive optical instrument by identifying possible degradations and determining negative influences on thermal and optical performance. The goal of the present work is to determine the relevant degradation mechanisms for the near-infrared spectrometers VenSpec-M and VEM at Venus and to identify possible degradations of different materials and coatings. To ensure the best possible performance of the instruments, the materials and coatings of the baffle unit exposed to the Venusian environment are selected in such a way that they exhibit the lowest possible degradation and do not negatively affect either the thermal or the optical performance of the instruments. Radiative analyses are performed using the ESATAN-TMS software with postprocessing done by coded Python scripts to quantify the environmental impact at Venus. Furthermore, a calculation method to estimate the expected atomic oxygen flux is developed, and further degradation sources are identified by appropriate research. A degradation analysis is performed, and its results are evaluated based on thermal analysis of the instruments in ESATAN-TMS. Final trade studies compare different pre-selected coatings and justify the selection of a recommended coating combination. Overall, it is concluded that organic coatings are particularly affected by atomic oxygen fluxes as well as solar and albedo radiation. Therefore, two ceramic and inorganic coatings were selected for the instrument’s baffle unit, Ceranovis V14 for the baffle shield made of AlMgSi10 and Acktar Fractal Black for the cone made of Ti-6Al-4V.