Flight measurement of molecular contaminant deposition

David F. Hall

doi:10.1117/12.190158

19 October 1994 Flight measurement of molecular contaminant deposition

David F. Hall

Proceedings Volume 2261, Optical System Contamination: Effects, Measurements, and Control IV; (1994) https://doi.org/10.1117/12.190158
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

Abstract

A spacecraft was instrumented with four temperature controlled quartz crystal microbalance (TQCM) contamination detectors. One TQCM, located inside the vehicle, recorded contaminant deposition that was orders of magnitude higher than did the three TQCMs located in various positions outside the vehicle. The deposition rate on the interior TQCM varied with the temperatures of interior spacecraft cavity surfaces. In particular, there is clear evidence of condensation on these surfaces and re-evaporation from these surfaces by previously outgassed contaminant molecules. The e-folding time constants of the deposition on two of the exterior TQCMs held at -50 degree(s)C are approximately 1.4 years, with extrapolated final equivalent thickness of the deposition in the 20 - 25 nm (200 - 250 angstroms) range. The third exterior TQCM, which has a significant field of view of a segmented thermal blanket, collected contamination at a greater rate. The data enable the ranking of the several contamination transport mechanisms at work and the drawing of general recommendations for spacecraft design.

Citation Download Citation

David F. Hall "Flight measurement of molecular contaminant deposition", Proc. SPIE 2261, Optical System Contamination: Effects, Measurements, and Control IV, (19 October 1994); https://doi.org/10.1117/12.190158

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