James Webb Space Telescope Initial On-Orbit Thermal Performance

The James Webb Space Telescope (JWST) is expected to be the premier space based astronomical observatory when it reaches its intended operational temperatures in the Spring of 2022. The cryogenic telescope portion features a deployed 6.5 meter primary mirror, backplane structure, and instrument complement passively cooled below 50Kelvin. Cooling to these temperatures is enabled by an L2 orbit, a 22x10 meter deployed sunshield, and numerous thermal isolation schemes. Proper observatory thermal performance will allow the scientific instruments to observe exoplanet formation, evolution of galaxies, and characteristics of the early universe. Prior to launch, extensive thermal testing was performed on a thermal simulator and the flight telescope to characterize on-orbit thermal performance including the ~120 day post-launch cooldown. This paper focuses on early JWST flight thermal performance, expected cryo-stable temperatures, and comparisons to test results and analytical predictions.