Determination of Emissivities of Key Thermo-Optical Surfaces on the James Webb Space Telescope

The James Webb Telescope (JWST) is a large cryo-optical system. Many critical thermal control or optical surfaces are exposed to ground and flight environments and are expected to be contaminated to some level. In order to calculate key system performance parameters, such as stray light and radiative thermal transfer, the emissivity must be known in terms of contamination level and temperature. This paper will introduce the methods of determining these emissivities, and the discussion will cover the types of particulate and molecular contamination expected on JWST. The results of the calculations will be introduced and discussed.