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26 February 2015 James Webb Space Telescope segment phasing using differential optical transfer functions
Johanan L. Codona, Nathan Doble
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Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 1, Issue 2, 029001 (February 2015). https://doi.org/10.1117/1.JATIS.1.2.029001
Abstract
Differential optical transfer function (dOTF) is an image-based, noniterative wavefront sensing method that uses two star images with a single small change in the pupil. We describe two possible methods for introducing the required pupil modification to the James Webb Space Telescope, one using a small (<λ/4) displacement of a single segment’s actuator and another that uses small misalignments of the NIRCam’s filter wheel. While both methods should work with NIRCam, the actuator method will allow both MIRI and NIRISS to be used for segment phasing, which is a new functionality. Since the actuator method requires only small displacements, it should provide a fast and safe phasing alternative that reduces the mission risk and can be performed frequently for alignment monitoring and maintenance. Since a single actuator modification can be seen by all three cameras, it should be possible to calibrate the non-common-path aberrations between them. Large segment discontinuities can be measured using dOTFs in two filter bands. Using two images of a star field, aberrations along multiple lines of sight through the telescope can be measured simultaneously. Also, since dOTF gives the pupil field amplitude as well as the phase, it could provide a first approximation or constraint to the planned iterative phase retrieval algorithms.
CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
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Johanan L. Codona and Nathan Doble "James Webb Space Telescope segment phasing using differential optical transfer functions," Journal of Astronomical Telescopes, Instruments, and Systems 1(2), 029001 (26 February 2015). https://doi.org/10.1117/1.JATIS.1.2.029001
Published: 26 February 2015
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Cited by 11 scholarly publications.
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KEYWORDS
Image segmentation
James Webb Space Telescope
Stars
Optical filters
Optical transfer functions
Point spread functions
Cameras
CHORUS Article. This article was made freely available starting 26 February 2016
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