Characterization of Vacuum Deposited Thin Organic Layers by Phase Shifting Interferometry and FTIR Spectroscopy for Space Contamination Study

Although satellites and spacecrafts are exposed to very small amounts of organic contamination (typically 10-9 to 10-5 g.cm-2 cumulated over their lifetime) from the outgassing of some of their own structural components, fixation and photo-degradation of organic compounds can significantly alter the thermo-optical properties of critical surfaces involved in their passive thermal regulation. The study of surface molecular contamination under conditions representative of space environment is therefore of prime interest in order to define mitigation strategies. The Centre Spatial de Liège has recently initiated research work on this topic and first experimental results are presented here. Organic thin films have been deposited using vacuum thermal evaporation / sublimation and their topology and equivalent surface concentration have been characterized using phase shifting interferometry. Furthermore, FT-IR spectroscopy in reflection configuration have been tested in different conditions in order to monitor the IR signature of contaminated surface samples this in the perspective of implementing an in situ monitoring system on a deposition chamber with UV exposure capability.