Abstract: The James Webb Space Telescope (JWST) is the largest cryogenic instrument telescope to be developed for space flight. The telescope will be passively cooled to 50 K and the instrument package will be at 40 K with the mid-infrared instrument at 6 K. The final cryogenic test of the Optical Telescope Element (OTE) and Integrated Science Instrument Module (ISIM) as an assembly (OTE + ISIM OTIS) will be performed in the largest 15 K chamber in the world, Chamber A at Johnson Space Center. The plan…