Development of robust thermo-optical thin-film membranes for the James Webb Space Telescope sunshield

The James Webb Space Telescope (JWST) observatory is the first segmented, deployed optical telescope with optical elements exposed to a space environment that will be thermally controlled to operate at cryogenic temperatures. A multilayered sunshield comprised of layers of polyimide film coated with alloyed silicon and multilayered aluminum based coatings has been developed to control the operating temperature of and minimize stray light seen by the Optical Telescope Element (OTE). The key requirements of the membrane material are to control thermal stability and steady-state thermal performance of the OTE, limit solar and infrared light transmission, meet ESD grounding requirements, have low contaminant levels, and to have highly durable, robust coatings. The testing that was done to evaluate the durability of the membrane material and to show that it will survive the fabrication, integration, test, and launch environments will be explored.