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Proceedings Paper

Target selection and imaging requirements for JWST fine phasing
Author(s): Joseph Jacob Green; Bruce H. Dean; Catherine M. Ohara; David C. Redding; Yan Zhang
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Paper 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 tp 10nm rms over 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.

Paper Details

Date Published: 12 October 2004
PDF: 10 pages
Proc. SPIE 5487, Optical, Infrared, and Millimeter Space Telescopes, (12 October 2004); doi: 10.1117/12.552433
Show Author Affiliations
Joseph Jacob Green, Jet Propulsion Lab. (United States)
Bruce H. Dean, NASA Goddard Space Flight Ctr. (United States)
Catherine M. Ohara, Jet Propulsion Lab. (United States)
David C. Redding, Jet Propulsion Lab. (United States)
Yan Zhang, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 5487:
Optical, Infrared, and Millimeter Space Telescopes
John C. Mather, Editor(s)

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