# Lettre de l'AT Exosystèmes n°25 (21 avril 2026)
Chères et chers collègues,
Voici les nouvelles de l'AT Exosystèmes du 2026-04-21 :
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1. Rappel: Sondage important de structuration de la communauté Exosystèmes France
2. Soutenance de thèse - 22 avril, 14h, Lisa Altinier
3. Présentations Exosystèmes V en ligne
4. Announcement of the PLATO ESP 2026 Conference
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1. Rappel: Sondage important de structuration de la communauté Exosystèmes France (deadline étendue!)
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L'Action Thématique Exosystèmes (AT-EXOS) est actuellement transverse aux programmes nationaux de Planétologie (PNP) et d'Astronomie & Astrophysique (PN-AA). Cette double affiliation n'a pas d'impact sur l'attribution des financements, mais elle engendre une charge de travail importante pour le comité d'expertise scientifique.
Dans ce contexte, nous souhaitons recueillir l'avis de la communauté quant à une éventuelle évolution de ce rattachement.
Serait-il pertinent d'associer l'AT-EXOS à un seul de ces programmes nationaux ? Si oui, à quel(s) programme(s) national(aux) l'AT-EXOS devrait-elle être rattachée ?
Merci de répondre au sondage d'ici le 23 mai (le sondage est trés rapide: 1 unique question).
https://beta.framadate.org/polls/a67bf5fc2ef438d03662
Le CES de l'AT-EXOS
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2. Soutenance de thèse - 22 avril, 14h, Lisa Altinier
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Dear all,
I am pleased to invite you to my PhD defence entitled "Development of high-order mode dithering: a new image processing method for exoplanet detection with the NASA Roman Space Telescope". The defence will take place on Wednesday, 22nd April at 2 p.m. in the LAM amphitheater. Please find the abstract and the jury composition below. The defence will be in english.
A zoom link will be available: https://univ-amu-fr.zoom.us/j/89104404673?pwd=lttga84L95jvLWpkb2b2taxm4R84MX.1
Members of the jury:
Sylvestre Lacour (LIRA, CNRS, Observatoire de Paris)-Reviewer and President
Gaël Chauvin (MPIA, Germany) - Reviewer
Vanessa Bailey (NASA JPL, USA) - Examiner
David Mouillet (IPAG, Université Grenoble Alpes) - Examiner
Arthur Vigan (LAM, CNRS, Marseille) - Thesis director
Élodie Choquet (LAM, CNRS, Marseille) - Thesis co-director
Abstract:
Direct imaging of exoplanets is crucial for characterizing their physical and atmospheric properties, but is challenging due to high contrast with host stars and small angular separations. Indirect methods like radial velocity and transits detect many exoplanets but provide limited atmospheric information. Achieving contrasts of ∼ 10−9 for Jupiter-like planets or ∼ 10−10 for Earth-like planets in reflected light exceeds current telescope capabilities. Ground-based adaptive optics detect young, infrared-bright planets, while Hubble and JWST lack active wavefront control for high contrast coronagraphy.
The Nancy Grace Roman Space Telescope (Roman, RST), launching in 2026, addresses this gap with a 2.4 m telescope and the first space-based coronagraph with active wavefront control. Its coronagraph can create a dark hole suppressing starlight to ∼ 10−9 after post-processing, enabling detection of old Jupiter-like planets at 3– 9 λ/D (0.15–0.44 arcsec). Quasi-static speckles from optical imperfections, thermal drifts, and DM actuator noise dominate the noise and require post-processing methods such as principle components analysis (PCA) and reference differential imaging (RDI).
Classical RDI is limited by wavefront drift and low reference star diversity. High-Order Mode Dithering (HOMD) injects controlled high-order aberrations (Z5–Z24) into deformable mirrors during reference star observations, enriching the speckle library and improving post-processing. CAPyBARA, a dedicated simulator, models the coronagraph and observing sequence, including static and quasi-static aberrations.
Results show HOMD effectiveness depends on drift, mode selection, and alignment with dominant aberrations. Low-order modes (Z5–Z8) provide the largest improvements, while partial overlap reduces effectiveness. HOMD increases library diversity, mitigates drift sensitivity, and improves post-processed contrast, providing a practical method to enhance space-based high-contrast imaging and paving the way for future missions like the Habitable Worlds Observatory, which will require extreme contrasts (∼ 10−10) for Earth-like planets detection.
I'm looking forward to see you on this day!
Best regards,
Lisa Altinier
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3. Présentations Exosystèmes V en ligne
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Il y a 3 semaines, la conférence Exosystèmes V a rencontré un vif succès, rassemblant plus de 120 participants. Le programme a notamment été enrichi par des présentations scientifiques de qualité, deux ateliers proposés par la communauté (Gaia & Océans de magma et sous-Neptunes), une table ronde dédiée à « La science des exoplanètes dans les années 2030: comment renforcer les synergies et notre positionnement ? » animée par six de nos collègues, ainsi qu'un atelier communautaire consacré aux discussions autour de l'AT-EXOS, l'INSU, le Groupe Transition environnementale de la CSAA, le CNES, le PEPR et la restructuration des SNOs. Merci à toutes et tous pour vos présentations de grandes qualités et votre participation!
Les présentations sont désormais disponibles en ligne, dans l'onglet « Programme » du site de la conférence : https://exosystemes5.sciencesconf.org
Enfin, nous vous donnons d'ores et déjà rendez-vous pour Exosystèmes VI, qui se tiendra du 4 au 8 octobre 2027 à Nice, à noter dès maintenant dans vos agendas ! La fréquence des ateliers Exosystèmes sera désormais tous les ~1.5 ans.
Le CES de l'AT-EXOS
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4. Announcement of the PLATO ESP 2026 Conference: Confronting planets across time and space at the University of Warwick, UK, from 16-18 September 2026
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Dear Colleagues,
The launch of the European Space Agency's exoplanet hunting mission PLATO is excitingly less than 1 year away!
PLATO (https://www.esa.int/Science_Exploration/Space_Science/Plato) will discover Earth-like planets orbiting bright stars, provide homogenous large-scale datasets of well-characterised planets, and unprecedentedly reveal the ages of exoplanet host stars. Therefore, this mission will revolutionise our knowledge of planets by understanding how they evolve over their lifetimes and how our Earth fits in the wider picture of planets spanning the Galaxy.
To galvanise and prime the wider exoplanet community for the PLATO mission, we are excited to announce the PLATO ESP 2026 Conference: Confronting planets across time and space at the University of Warwick, UK, from 16-18 September 2026.
This meeting is open to all and aims to bring together observers, theorists, and instrumentalists to discuss how planets form and evolve, and how the upcoming PLATO datasets will transform our wider understanding.
The registration will open in May 2026 with more information on the conference here: https://warwick.ac.uk/fac/sci/physics/research/astro/research/meetings/platoesp2026/
Early career researchers (ECRs) are particularly encouraged to attend with limited funding support available.
Best wishes,
Tom Wilson
on behalf of the Scientific Organising Committee:
Suzanne Aigrain (University of Oxford)
David Brown (University of Warwick) - co-chair
Juan Cabrera (DLR)
Magali Deleuil (LAM)
Lauren Doyle (University of Warwick) - co-chair
Ana Heras (ESA)
Hugh Osborn (University of Bern)
Isabella Pagano (INAF)
Giampaolo Piotto (University of Padova)
Don Pollacco (University of Warwick)
Heike Rauer (DLR/FU Berlin)
Sophia Sulis (LAM)
Stephane Udry (University of Geneva)
Tom Wilson (University of Warwick) - Chair