Wavefront Sensing and Control
The James Webb Space Telescope architecture includes a 6.5 meter diameter telescope having a segmented primary mirror that will deploy after it launches. To perform like a single monolithic mirror, a wavefront sensing and control subsystem is required to sense and then correct any errors in the optics.
Each of the 9 distinct alignment processes - the algorithms - needed to align the deployed telescope into a high-performance astronomical telescope have been designed and demonstrated on the testbed.
For more technical information on the wavefront sensing and control testing process, please view the article in Newsletter #2.
A few additional photos fully functional, 1/6th scale model of the JWST mirror in its optics testbed (images credit: NASA):
Here are two videos showing the scaled telescope testbed for wavefront sensing and control testing.