Optical performance verification of the James Webb Space Telescope

The James Webb Space Telescope (JWST) is a large aperture (6.6 m primary mirror) cryogenic telescope with active control of the segmented primary and secondary mirror optical elements. The architecture of the telescope makes full end-to-end testing on the ground prohibitive due to both cost and technical considerations. Additionally, because the telescope will be launched in a folded configuration to fit in the Ariane V launch fairing and aligned during flight using image-based Wavefront Sensing and Control (WFS&C), the telescope cannot be tested in the classical "test-as-you-fly" architecture. Due to these considerations, the primary optical performance requirements will be verified through analysis. In order to have high confidence in this approach, a robust analysis validation program has been developed based on testing from the component level through the integrated telescope level. This verification approach focuses on ground testing at the telescope level to ensure there will be adequate range in the adjustable optics for alignment on orbit. In addition to the incremental test program planned for optical verification, a double-pass sampled aperture test of the integrated telescope and instruments is planned at flight-like temperatures as a crosscheck to the analytic verification for flight. Error budgets have been developed to understand the uncertainty propagation through the test and analysis program.