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Title: Target selection and imaging requirements for JWST fine phasing
Authors: Green, Joseph J.
Dean, Bruce H.
Ohara, Catherine M.
Zhang, Yan
Keywords: wavefront sensing
focus diversity
James Webb Space Technolgoy
Issue Date: 21-Jun-2004
Publisher: Pasadena, CA : Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2004.
Citation: SPIE Astronomical Telescopes and Instrumentation, Glasgow, Scotland, June 21, 2004.
Abstract: To achieve and maintain the fine alignment of its segmented primary mirror the James Webb Space Telescope (JWST) plans to use focus-diverse wavefront sensing (WFS) techniques with science camera imagery. The optical requirements for JWST are such that the error contribution from the WFS itself must be limited 10nm rms over all the controllable degrees of freedom of the telescope. In this paper, we will explore the requirements on the target selection and imaging requirements necessary to achieve the desired level of WFS accuracy. Using Monte Carlo simulations we explore the WFS error as a function of wavefront aberrations level, defocus-diversity level, optical bandwidth and imaging signal-to-noise ratio to establish the key imaging requirements. By taking into account practical integration time limits along with the distribution of the defocused point-spread functions, we establish the bright and faint star magnitude limits suitable for WFS target selection.
Appears in Collections:JPL TRS 1992+

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