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Validation of strategies for coupling exoplanet PSFs into single-mode fibres for high-dispersion coronagraphy

El Morsy, M.; Vigan, A.; Lopez, M.; Otten, G.P.P.L.; Choquet, E.; Madec, F.; Costille, A.; Sauvage, J.-F.; Dohlen, K.; Muslimov, E.; Pourcelot, R.; Floriot, J.; Benedetti, J.-A.; Blanchard, P.; Balard, P.; Murray, G.

Validation of strategies for coupling exoplanet PSFs into single-mode fibres for high-dispersion coronagraphy Thumbnail


M. El Morsy

A. Vigan

M. Lopez

G.P.P.L. Otten

E. Choquet

F. Madec

A. Costille

J.-F. Sauvage

K. Dohlen

E. Muslimov

R. Pourcelot

J. Floriot

J.-A. Benedetti

P. Blanchard

P. Balard


On large ground-based telescopes, the combination of extreme adaptive optics (ExAO) and coronagraphy with high-dispersion spectroscopy (HDS), sometimes referred to as high-dispersion coronagraphy (HDC), is starting to emerge as a powerful technique for the direct characterisation of giant exoplanets. The high spectral resolution not only brings a major gain in terms of accessible spectral features, but also enables a better separation of the stellar and planetary signals. Ongoing projects such as Keck/KPIC, Subaru/REACH, and VLT/HiRISE base their observing strategy on the use of a few science fibres, one of which is dedicated to sampling the planetŠs signal, while the others sample the residual starlight in the speckle field. The main challenge in this approach is to blindly centre the planet’s point spread function (PSF) accurately on the science fibre, with an accuracy of less than 0.1 λ/D to maximise the coupling efficiency. In the context of the HiRISE project, three possible centring strategies are foreseen, either based on retro-injecting calibration fibres to localise the position of the science fibre or based on a dedicated centring fibre. We implemented these three approaches, and we compared their centring accuracy using an upgraded setup of the MITHiC high-contrast imaging testbed, which is similar to the setup that will be adopted in HiRISE. Our results demonstrate that reaching a specification accuracy of 0.1 λ/D is extremely challenging regardless of the chosen centring strategy. It requires a high level of accuracy at every step of the centring procedure, which can be reached with very stable instruments. We studied the contributors to the centring error in the case of MITHiC and we propose a quantification for some of the most impacting terms.

Journal Article Type Article
Acceptance Date May 9, 2022
Online Publication Date Nov 25, 2022
Publication Date 2022
Deposit Date Mar 6, 2023
Publicly Available Date Mar 6, 2023
Journal Astronomy & Astrophysics
Print ISSN 0004-6361
Electronic ISSN 1432-0746
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 667
Article Number A171
Public URL


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Copyright Statement
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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