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1.1 This practice provides guidance for making decisions concerning the use of a quartz crystal microbalance (QCM) and a thermoelectrically cooled quartz crystal microbalance (TQCM) in space where contamination problems on spacecraft are likely to exist. Careful adherence to this document should ensure adequate measurement of condensation of molecular constituents that are commonly termed “contamination” on spacecraft surfaces.

1.2 A corollary purpose is to provide choices among the flight-qualified QCMs now existing to meet specific needs.

1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

5.1 Spacecraft have consistently had the problem of contamination of thermal control surfaces from line-of-sight warm surfaces on the vehicle, outgassing of materials and subsequent condensation on critical surfaces, such as solar arrays, moving mechanical assemblies, cryogenic insulation schemes, and electrical contacts, control jet effects, and other forms of expelling molecules in a vapor stream. To this has been added the need to protect optical components, either at ambient or cryogenic temperatures, from the minutest deposition of contaminants because of their absorptance, reflectance or scattering characteristics. Much progress has been accomplished in this area, such as the careful testing of each material for outgassing characteristics before the material is used on the spacecraft (following Test Methods E595 and E1559), but measurement and control of critical surfaces during spaceflight still can aid in the determination of location and behavior of outgassing materials.