Preparation and cleanliness verifications of a space simulation chamber for contamination sensitive test specimens

Contamination sensitive optical devices were to be evaluated under thermal vacuum conditions. Test specifications called for an extremely clean chamber environment, ambient temperature chamber walls, and optical surface temperatures at approximately - 30 C. Chamber preparation included the replacement of diffusion pumps with cryopumps and the cleaning of the chamber walls to reduce contamination levels. Chamber cleaning using vacuum bake was tried and abandoned as time consuming and ineffective. Chemical cleaning and cleanliness verification methods were developed. Gas chromatograph analysis techniques were used extensively throughout the cleaning process to verify cleanliness levels prior to evacuating the chamber. A chamber cleanliness verification test using a thermoelectric quartz crystal microbalance and witness samples was performed to demonstrate that an appropriate cleanliness level was achieved.