10 June 2006 Verification of the James Webb Space Telescope coarse phase sensor using the Keck Telescope
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The James Webb Space Telescope (JWST) Coarse Phase Sensor utilizes Dispersed Hartmann Sensing (DHS)1 to measure the inter-segment piston errors of the primary mirror. The DHS technique was tested on the Keck Telescope. Two DHS optical components were built to mate with the Keck optical and mechanical interfaces. DHS images were acquired using 20 different primary mirror configurations. The mirror configurations consisted of random segment pistons applied to 18 of the 36 segments. The inter-segment piston errors ranged from phased (approximately 0 μm) to as large as ±25 μm. Two broadband exposures were taken for each primary mirror configuration: one for the DHS component situated at 0°, and one for the DHS component situated at 60°. Finally, a "closed-loop" DHS sensing and control experiment was performed. Sensing algorithms developed by both Adaptive Optics Associates (AOA) and the Jet Propulsion Laboratory (JPL)2 were applied to the collected DHS images. The inter-segment piston errors determined by the AOA and JPL algorithms were compared to the actual piston steps. The data clearly demonstrates that the DHS works quite well as an estimator of segment-to-segment piston errors using stellar sources.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Marc Albanese, Marc Albanese, Allan Wirth, Allan Wirth, Andrew Jankevics, Andrew Jankevics, Tom Gonsiorowski, Tom Gonsiorowski, Catherine Ohara, Catherine Ohara, Fang Shi, Fang Shi, Mitchell Troy, Mitchell Troy, Gary Chanan, Gary Chanan, Scott Acton, Scott Acton, } "Verification of the James Webb Space Telescope coarse phase sensor using the Keck Telescope", Proc. SPIE 6265, Space Telescopes and Instrumentation I: Optical, Infrared, and Millimeter, 62650Z (10 June 2006); doi: 10.1117/12.672055; https://doi.org/10.1117/12.672055

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