Contamination may be simply defined as any foreign matter. In general, contamination is grouped into two broad categories labeled molecular and particulate. Molecular contamination refers to the cumulative buildup of individual molecules of foreign matter. An example of molecular contamination is the familiar ânew car smell,â which is the odor of plastics such as vinyl. These are indications of volatile molecules being generated, or outgassed, by organic materials. Particulate contamination refers to the deposition of visible Î¼m-sized conglomerations of matter. Surfaces that become dusty and eyeglasses that require periodic wiping are an indication of the presence of particles in the atmosphere. The process of preventing contamination from degrading the performance of a surface, or system, is called contamination control. As evidenced by the wealth of material published on the subject, contamination control is an important subject. High-profile remote sensing missions, such as the Hubble Space Telescope, must devote significant resources to contamination control. Even in the absence of remote sensing payloads, long-lived spacecraft like the International Space Station (ISS) must also plan for extensive contamination control measures. Numerous contamination-related risk mitigation studies, such as the Optical Properties Monitor (OPM), Space Portable SpectroReflectometer (SPSR) or Mir Environmental Effects Payload (MEEP), were conducted before ISS assembly began.
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