How do you control contamination for sensitive spacecraft instruments?

Contamination degrades optical, thermal, and electrical performance. Sources: Manufacturing residues, Outgassing from materials, Propulsion exhaust, Venting products, and Particle generation from mechanisms. Control program: Design phase - Material selection (low outgassing, ASTM E595), Contamination budget allocation, and Keep-out zones for sensitive surfaces. Fabrication - Precision cleaning procedures, Cleanroom assembly (Class 10,000 or better), Bakeout of materials, and Witness samples for monitoring. Testing - Maintain cleanliness during I&T, Contamination covers until last moment, and Particulate and molecular monitoring. Flight - Heater decontamination of optics, Pointing away from exhaust, and Careful thruster activation sequences. Analysis: Outgassing modeling (view factors to sensitive surfaces), Molecular transport analysis (TRASYS, Monte Carlo), and Particulate redistribution during events. Critical for: Optical telescopes, Thermal control surfaces, Solar cells, and Cryogenic instruments.