From its orbit around the Earth-Sun second Lagrange point some million miles from Earth, the James Webb Space Telescope (JWST) will be uniquely suited to study early galaxy and star formation with its suite of infrared instruments. [1] To maintain exceptional image quality using its 6.6 meter segmented primary mirror, wavefront sensing and control (WFS&C) is vital to ensure the optical alignment of the telescope throughout the mission. After deployment of the observatory structure and mirrors from the "folded" launch configuration, WFS&C is used to align the telescope [2] , as well as maintain that alignment. WFS&C verification includes the verification of the software and its incorporated algorithms, along with the supporting aspects of the integrated ground segment, instrumentation, and telescope through increasing levels of assembly. The software and process are verified with the Integrated Telescope Model (ITM), which is a Matlab/Simulink integrated observatory model which interfaces to CodeV/OSLO/IDL. In addition to lower level testing, the Near-Infrared Camera [3] (NIRCam) with its wavefront sensing optical components is verified with the other instruments with a cryogenic optical telescope simulator (OSIM) before moving on to the final WFS&C testing in Chamber A at the Johnson Space Center (JSC) where additional observatory verification occurs.
By segmenting and folding the primary mirror, quite large telescopes can be packed into the nose cone of a rocket. Deployed after launch, initial optical performance can be quite poor, due to deployment errors, thermal deformation, fabrication errors and other causes. We describe an automatic control system for capturing, aligning, phasing, and deforming the optics of such a telescope, going from initial cm-level wavefront errors to diffraction-limited observatory operations. This system was developed for the Next Generation Space Telescope and is being tested on the NGST Wavefront Control Testbed.
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