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Extremely tight thermal control property degradation allowances on the vapor-deposited, gold-coated IEC baffle surface, made necessary by the cryogenic JWST Observatory operations, dictate tight contamination requirements on adjacent surfaces. Theoretical degradation in emittance with contaminant thickness was calculated. Maximum allowable source outgassing rates were calculated using worst case view factors from source to baffle surface. Tight requirements pushed the team to change the design of the adjacent surfaces to minimize the outgassing sources.

This paper will continue from Part 1 of JWST contamination control implementation. In addition to optics, instruments, and thermal vacuum testing, JWST also requires contamination control for a spacecraft that must be vented carefully in order to maintain solar array and thermal radiator thermal properties; a tennis court-sized sunshield made with 1-2 mil Kapton™ layers that must be manufactured and maintained clean; an observatory that must be integrated, stowed and transported to South America; and a rocket that typically launches commercial payloads without contamination sensitivity. An overview of plans developed to implement contamination control for the JWST spacecraft, sunshield, observatory and launch vehicle will be presented. IV. SPACECRAFT JWST requires contamination control for a spacecraft that must be vented carefully in order to maintain solar array and thermal radiator thermal properties.This discussion will focus on the hot side of the JWST observatory, on which the primary drivers for contamination control are the EOL molecular requirement of 200Å on the Solar Arrays and Radiators and of 300Å on the sunshield. As a result, the outgassing rates of importance are those with direct and indirect line of sight to the Solar Arrays, Optical Solar Reflectors (OSRs -these make up the thermal radiators), and Sunshield. Spacecraft surfaces, not including the sunshield, are shown in Figure 1.

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