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First on-sky demonstration of spatial Linear Dark Field Control with the vector-Apodizing Phase Plate at Subaru/SCExAO

Bos, S. P. and Miller, K. L. and Lozi, J. and Guyon, O. and Doelman, D. S. and Vievard, S. and Sahoo, A. and Deo, V. and Jovanovic, N. and Martinache, F. and Currie, T. and Snik, F. (2021) First on-sky demonstration of spatial Linear Dark Field Control with the vector-Apodizing Phase Plate at Subaru/SCExAO. Astronomy and Astrophysics, 653 . Art. No. A42. ISSN 0004-6361. doi:10.1051/0004-6361/202040134.

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Context. One of the key noise sources that currently limits high-contrast imaging observations for exoplanet detection is quasi-static speckles. Quasi-static speckles originate from slowly evolving non-common path aberrations (NCPA). These NCPA are related to the different optics encountered in the wavefront sensing path and the science path, and they also exhibit a chromatic component due to the difference in the wavelength between the science camera and the main wavefront sensor. These speckles degrade the contrast in the high-contrast region (or dark hole) generated by the coronagraph and make the calibration in post-processing more challenging. Aims. The purpose of this work is to present a proof-of-concept on-sky demonstration of spatial Linear Dark Field Control (LDFC). The ultimate goal of LDFC is to stabilize the point spread function by addressing NCPA using the science image as additional wavefront sensor. Methods. We combined spatial LDFC with the Asymmetric Pupil vector-Apodizing Phase Plate (APvAPP) on the Subaru Coronagraphic Extreme Adaptive Optics system at the Subaru Telescope. To allow for rapid prototyping and easy interfacing with the instrument, LDFC was implemented in Python. This limited the speed of the correction loop to approximately 20 Hz. With the APvAPP, we derive a high-contrast reference image to be utilized by LDFC. LDFC is then deployed on-sky to stabilize the science image and maintain the high-contrast achieved in the reference image. Results. In this paper, we report the results of the first successful proof-of-principle LDFC on-sky tests. We present results from two types of cases: (1) correction of instrumental errors and atmospheric residuals plus artificially induced static aberrations introduced on the deformable mirror and (2) correction of only atmospheric residuals and instrumental aberrations. When introducing artificial static wavefront aberrations on the DM, we find that LDFC can improve the raw contrast by a factor of 3–7 over the dark hole. In these tests, the residual wavefront error decreased by ∼50 nm RMS, from ∼90 nm to ∼40 nm RMS. In the case with only residual atmospheric wavefront errors and instrumental aberrations, we show that LDFC is able to suppress evolving aberrations that have timescales of < 0.1–0.4 Hz. We find that the power at 10⁻² Hz is reduced by a factor of ∼20, 7, and 4 for spatial frequency bins at 2.5, 5.5, and 8.5λ/D, respectively. Conclusions. We have identified multiplied challenges that have to be overcome before LDFC can become an integral part of science observations. The results presented in this work show that LDFC is a promising technique for enabling the high-contrast imaging goals of the upcoming generation of extremely large telescopes.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Miller, K. L.0000-0003-4716-5657
Lozi, J.0000-0002-3047-1845
Guyon, O.0000-0002-1097-9908
Doelman, D. S.0000-0003-0695-0480
Vievard, S.0000-0003-4018-2569
Sahoo, A.0000-0003-2806-1254
Deo, V.0000-0003-4514-7906
Jovanovic, N.0000-0001-5213-6207
Martinache, F.0000-0003-1180-4138
Currie, T.0000-0002-7405-3119
Snik, F.0000-0003-1946-7009
Additional Information:© ESO 2021. Article published by EDP Sciences. Received 15 December 2020; Accepted 27 May 2021; Published online 07 September 2021. Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. S. P. Bos and K. L. Miller have contributed equally to this work. The authors thank the referee for comments on the manuscript that improved this work. The research of S. P. Bos and F. Snik leading to these results has received funding from the European Research Council under ERC Starting Grant agreement 678194 (FALCONER). The development of SCExAO was supported by the Japan Society for the Promotion of Science (Grant-in-Aid for Research #23340051, #26220704, #23103002, #19H00703 & #19H00695), the Astrobiology Center of the National Institutes of Natural Sciences, Japan, the Mt Cuba Foundation and the director’s contingency fund at Subaru Telescope. LDFC development at SCExAO was supported by the NASA Strategic Astrophysics Technology (SAT) Program grant #80NSSC19K0121. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are very fortunate to have the opportunity to conduct observations from this mountain. This research made use of HCIPy, an open-source object-oriented framework written in Python for performing end-to-end simulations of high-contrast imaging instruments (Por et al. 2018). This research used the following Python libraries: Scipy (Jones et al. 2014), Numpy (van der Walt 2011), and Matplotlib (Hunter 2007).
Funding AgencyGrant Number
European Research Council (ERC)678194
Japan Society for the Promotion of Science (JSPS)23340051
Japan Society for the Promotion of Science (JSPS)26220704
Japan Society for the Promotion of Science (JSPS)23103002
Japan Society for the Promotion of Science (JSPS)19H00703
Japan Society for the Promotion of Science (JSPS)19H00695
National Institutes of Natural Sciences of JapanUNSPECIFIED
Mt. Cuba Astronomical FoundationUNSPECIFIED
Subaru TelescopeUNSPECIFIED
Subject Keywords:instrumentation: adaptive optics – instrumentation: high angular resolution
Record Number:CaltechAUTHORS:20211006-141412646
Persistent URL:
Official Citation:First on-sky demonstration of spatial Linear Dark Field Control with the vector-Apodizing Phase Plate at Subaru/SCExAO. S. P. Bos, K. L. Miller, J. Lozi, O. Guyon, D. S. Doelman, S. Vievard, A. Sahoo, V. Deo, N. Jovanovic, F. Martinache, T. Currie and F. Snik. A&A, 653 (2021) A42; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111233
Deposited By: Tony Diaz
Deposited On:06 Oct 2021 14:38
Last Modified:06 Oct 2021 14:38

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