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Proceedings Paper

Electric field conjugation in the presence of model uncertainty
Author(s): David Marx; Byoung-Joon Seo; Brian Kern; Erkin Sidick; Bijan Nemati; Ilya Poberezhskiy
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Paper Abstract

The Wide-Field Infrared Survey Telescope (WFIRST) is a 2.4m diameter space telescope NASA program. The payload will include a coronagraph instrument (CGI). The CGI designs under development use deformable mirrors (DM) to create a point spread function (PSF) with a dark region around the obscured star object. Electric field conjugation (EFC) is an iterative nonlinear optimization procedure that uses measurements of the electric field at the image to determine the DM displacements that modify the PSF to create the region of high contrast in the image. EFC requires a numerical model of the coronagraph to calculate the Jacobian of the system, which is used, along with regularization, to solve for the DM displacements for each iteration of the nonlinear optimization. Ideally, the coronagraph is aligned and calibrated, and the calibration data are used in the numerical model for calculating the Jacobian. However, calibration and alignment measurements always contain uncertainty resulting in calibration error. Therefore, the Jacobian calculated from the numerical model is not an exact representation of the physical coronagraph, and the resulting DM solution for an EFC iteration does not have the exact impact on the electric field of the coronagraph as predicted by the EFC. The result is slow convergence, and, as will be shown, the necessity of more restrictive regularization. Using Monte Carlo trials, we investigate the effect of calibration error on EFC convergence and regularization. Comparison to results from the High Contrast Imaging Testbed Hybrid Lyot Coronagraph are also presented.

Paper Details

Date Published: 1 September 2017
PDF: 9 pages
Proc. SPIE 10400, Techniques and Instrumentation for Detection of Exoplanets VIII, 104000P (1 September 2017); doi: 10.1117/12.2274541
Show Author Affiliations
David Marx, Jet Propulsion Lab. (United States)
Byoung-Joon Seo, Jet Propulsion Lab. (United States)
Brian Kern, Jet Propulsion Lab. (United States)
Erkin Sidick, Jet Propulsion Lab. (United States)
Bijan Nemati, Jet Propulsion Lab. (United States)
Ilya Poberezhskiy, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 10400:
Techniques and Instrumentation for Detection of Exoplanets VIII
Stuart Shaklan, Editor(s)

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