Issue |
A&A
Volume 666, October 2022
|
|
---|---|---|
Article Number | A91 | |
Number of page(s) | 10 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361/202243413 | |
Published online | 13 October 2022 |
Redundant apodization for direct imaging of exoplanets
II. Application to island effects
1
Univ. Grenoble Alpes, CNRS, IPAG,
38000
Grenoble, France
e-mail: lucie.leboulleux@univ-grenoble-alpes.fr
2
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange,
06108
Nice, France
3
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris,
5 place Jules Janssen,
92195
Meudon, France
4
Department of Astronomy, California Institute of Technology,
Pasadena, CA
91125, USA
5
Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326,
13388
Marseille, France
6
European Southern Observatory (ESO),
Karl-Schwarzschild-Str. 2,
85748
Garching bei Muenchen, Germany
Received:
24
February
2022
Accepted:
21
May
2022
Context. Telescope pupil fragmentation from spiders generates specific aberrations that have been observed at various telescopes and are expected on the 30-meter class telescopes under construction. This is known as the island effect, and it induces differential pistons, tips, and tilts on the pupil petals, deforming the instrumental point spread function (PSF); it is one of the main limitations to the direct detection of exoplanets with high-contrast imaging. These petal-level aberrations can have different origins such as the low-wind effect or petaling errors in the adaptive optics reconstruction.
Aims. In this paper, we propose a method for alleviating the impact of the aberrations induced by island effects on high-contrast imaging by adapting the coronagraph design in order to increase its robustness to petal-level aberrations.
Methods. Following a method first developed and applied on robustness to errors due to primary mirror segmentation (e.g., segment phasing errors, missing segments), we developed and tested redundant apodized pupils (RAP): apodizers designed at the petal-scale, then duplicated and rotated to mimic the pupil petal geometry.
Results. We applied this concept to the ELT architecture, made of six identical petals, to yield a 10−6 contrast in a dark region from 8 to 40λ/D. Both amplitude and phase apodizers proposed in this paper are robust to differential pistons between petals, with minimal degradation to their coronagraphic PSFs and contrast levels. In addition, they are also more robust to petal-level tip-tilt errors than classical apodizers designed for the whole pupil, with which the limit of contrast of 10−6 in the coronagraph dark zone is achieved for constraints up to 2 rad RMS of these petal-level modes.
Conclusions. In this paper the RAP concept proves its robustness to island effects (low-wind effect and post-adaptive optics petaling), with an application to the ELT architecture. It can also be considered for other 8- to 30-m class ground-based units such as VLT/SPHERE, Subaru/SCExAO, GMT/GMagAO-X, and TMT/PSI.
Key words: atmospheric effects / turbulence / instrumentation: high angular resolution / techniques: high angular resolution / telescopes / planets and satellites: detection
© L. Leboulleux et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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