Nanometer level characterization of the James Webb Space Telescope optomechanical systems using high-speed interferometry

The James Webb Space Telescope (JWST) Optical Telescope Element is a three mirror anastigmat consisting of a 6.5 m segmented primary mirror (PM), a secondary mirror, and a tertiary mirror. The primary mirror comprises 18 individual hexagonal segments. The telescope and instruments will be assembled at Goddard Space Flight Center (GSFC) to build the Optical Telescope Element-Integrated Science Instrument Module (OTIS). While at GSFC, the OTIS will go through a series of environmental tests. In these tests the OTIS will be exposed to launch level acoustics and vibrations. To assure that OTIS’s performance has not changed due to these environmental tests, the assembly will be tested optically at the center of curvature of the PM. A high-speed interferometer has been designed and built to characterize both static and dynamic changes due to environmental exposure. This paper describes the details of these measurement techniques. To validate and develop the techniques that will be used on OTIS assembly two spare JWST PM segments were measured and the results presented here.