To ensure the cleanliness of sensitive spacecraft systems, the contamination environment in aerospace cleanrooms and highbays is closely monitored. In this paper, we report the testing and evaluation of a commercially available molecular contamination monitor consisting of a 200-MHz surface acoustic wave microbalance (SAWM). SAWMs were placed into four different aerospace facilities with markedly different environments. SAWMs measured distinctly different molecular film accretion rates consistent with the levels of contamination control and activity in each facility. SAWM results were compared with nonvolatile residue (NVR) accretion rates measured by witness plates. Witness plate data yielded a higher NVR accretion rate than microbalance data. We present evidence that this difference is due to the detection limit of the witness plate analysis technique and not to a fundamental difference in surface deposition processes.

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