A state diagram operations plan for James Webb Space Telescope cryogenic vacuum testing

Space environment simulation testing can involve many complex and interdependent operations. A fundamental issue when defining these tests is the organization of information into a format that is understandable by reviewers and contributors. Plans are typically developed by simple combination of written procedures for individual systems. State diagram methodology was instead used to address the test definition problem for facility operations supporting a large-scale, long-duration space environment test of the James Webb Space Telescope (JWST) inside the Chamber A facility at NASA's Johnson Space Center (JSC) in Houston, Texas. The state diagram technique selected for the JWST test is described and associated models are presented. This includes processes required to operate the cryogenic vacuum chamber and its support systems during both nominal and off-nominal conditions. Utilizing state diagram abstraction methods for JWST cryogenic vacuum test planning has facilitated refinement of the test processes and has expedited the orientation process for stakeholders with various technical backgrounds.