Maintaining a dark hole in a high contrast coronagraph and the effects of speckles drift on contrast and post processing factor

Leonid Pogorelyuk; N. Jeremy Kasdin

doi:10.1117/12.2528283

9 September 2019 Maintaining a dark hole in a high contrast coronagraph and the effects of speckles drift on contrast and post processing factor

Leonid Pogorelyuk, N. Jeremy Kasdin

Author Affiliations +

Proceedings Volume 11117, Techniques and Instrumentation for Detection of Exoplanets IX; 1111718 (2019) https://doi.org/10.1117/12.2528283
Event: SPIE Optical Engineering + Applications, 2019, San Diego, California, United States

Abstract

The speckles pattern in the imaging plane of a high contrast coronagraph is highly sensitive to perturbations of the wavefront in the pupil plane. As these wavefront errors vary in time, they may significantly increase the intensity of the speckles and thus impose overly stringent constraints on wavefront stability. A recently proposed solution is to perform a recursive estimation of the speckles field and reduce its intensity via Electric Field Conjunction (EFC), both done while continuously observing the target star. For accuracy purposes, this estimation procedure requires introducing phase diversity in the imaging plane which is done via dithering the deformable mirror controls around their optimal EFC value. The faster the speckles drift, the more dithering is necessary for the controller to remain stable, hence more starlight is introduced into the dark hole and the post processing factor (the dimmest exoplanet that can be observed) decreases. Using a model of the Wide- Field Infra-Red Survey Telescope (WFIRST) Coronagraph Instrument (CGI), we illustrate the effects of drift magnitude on the best contrast achieved by the dark hole maintenance scheme. We then consider the resulting post-processing factors corresponding to a posteriori estimates of the intensity of sources incoherent with the star.

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Leonid Pogorelyuk and N. Jeremy Kasdin "Maintaining a dark hole in a high contrast coronagraph and the effects of speckles drift on contrast and post processing factor", Proc. SPIE 11117, Techniques and Instrumentation for Detection of Exoplanets IX, 1111718 (9 September 2019); https://doi.org/10.1117/12.2528283

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