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Accueil > Recherche > Groupe R&D Optique & Instrumentation > Workshops > AO4ASTRO@Marseille 2019

 AO4ASTRO@Marseille 2019

We host the workshop AO4ASTRO at Marseille on March 26th to 28th 2019. More information can be found below :

Contacts :
Thierry FUSCO


In order to get the best science results out of the AO-system images, and to fully optimize the return of such complex systems, dedicated and optimized reduction tools are needed. These tools must be built with a deep understanding of the system performance and limitations, and must be adapted to each science objectives. Toward these goals, the objective of the workshop is to gather both astronomers, AO specialist and data handling experts, in order to discuss new data reduction and analysis tools for current and future AO systems.

Those topics will be addressed in the light of the data obtained on 8/10 m telescopes and will draw a roadmap for the preparation of data processing tools on future 30/40 m class telescopes.

Abstract Submission

The submission and registration procedure is the following :

Send a email to Olivier BELTRAMO-MARTIN in which you will indicate if you want to
1) register only
2) submit an oral presentation or a poster

in the last case please add
1) the title of the communication
2) a short abstract (500 words max)

The deadline for both submissions and registrations is the 25th of January 2019

Please note that the number of place will be limited to 60 max (room capacity). Speakers willing to share their talks will have theirs presentations stored into the LAM broadcasting system and available publicly.
Thank to the support of our partners and sponsors, there will be no registration fees for this workshop.
Presentations and discussions will be broadcast and stored. Comments and questions from external attendees can be done through the workshop twitter account @Ao4Astro #ao4astro


Valentina Abril LAM
Lia Athanassoula LAM
Roland Bacon CRAL
Olivier Beltramo-Martin ONERA/LAM
Felix Bosco MPIA
Nicolas Bouché CRAL
Hugo Buddelmeijer Kapteyn Astronomical Institute, Groningen University
Yoann Brûlé LAM
Faustine Cantalloube MPIA
Marcel Carbillet (remote) OCA
Elena Carolo INAF Padova
Yixian Cao LAM
Laure Catala GEMINI
Élodie Choquet LAM
Simon Conseil CRAL
Carlos M. Correia LAM
Hervé Le Coroller LAM
Julian Christou LBT Observatory
Carl-Henrik Dahlqvist STAR - U. Liege
Marcos Van Dam (remote) Flat Wavefront
Ric Davies MPE-MPG
Richard Mc Dermid (remote) ANU
François-Xavier Dupé LIS
Benoit Épinat LAM
Markus Feldt MPIA
Florian Ferreira LESIA
Romain Fétick ONERA/LAM
Giuliana Fiorentino INAF
Thierry Fusco ONERA/LAM
Luc Giles (remote) TMT
Christophe Giordano OCA
Morgan Gray CESAM/LAM
Laurent Jolissaint HEIGV
Sidonie Lefebvre (remote) ONERA
Miska Le Louarn ESO
Junais Madathodika LAM
Antonino Marasco U. Groningen
Elena Masciadri (remote) INAF
Davide Massari University of Groningen
Alvaro Menduina U. Oxford
Julien Milli ESO
Estelle Moraux IPAG
Laurent Mugnier ONERA
Minerva Munoz LAM
Rakesh Nath U. Liege
Benoit Neichel LAM
Gilles Otten LAM
Matthieu Puech GEPI
François Rigaut ANU
Matthias Rosensteiner MPE-MPG
Lauren Schatz LAM
Garima Singh LESIA
Gaetano Sivo GEMINI
Matthias Tecza U. Oxford
Paolo Turri UC Berkeley
Niranjan Thatte U. Oxford
Gabriele Umbriaco Universita degli Studi di Padova
Daniele Vassalo INAF Padova
Arthur Vigan LAM
Roland Wagner JKU Linz
Gunther Witzel MPG
Annie Zavagno LAM


Session 1 : Spectrographs IFU (Tuesday)
13:30 Introduction O. Beltramo-Martin (ONERA/LAM)
13:45 Invited Talk : Learning to inverse F.-X. Dupé (LIS)
14:20 Invited Talk : Get the best science with AO : lessons learned with MUSE R. Bacon (CRAL)
14:55 The role and limitations of the PSF in a forward model with GalPaK3D N. Bouché (CRAL)
15:15 PSF reconstruction for MUSE Wide Field Mode. Final on-sky performance and routine operations. T. Fusco (LAM)
15:35 Break
16:00 Gemini North Adaptive Optics (GNAO) : an MCAO system for Gemini North F. Catala/G. Sivo (Gemini)
16:20 HARMONI science simulations with HSIM : Knowledge of the PSF N. Thatte (Oxford)
16:40 NCPA calibration with Machine Learning in ELT-HARMONI A. Menduina (Oxford)
17:00 MOSAIC : preparing phase B M. Puech (GEPI)
17:20 Open discussion Day 1
19:00 Evening event @ LA NAUTIQUE
Session 2 : Vis./NIR imaging (Wednesday)
09:00 Invited Talk : Enhancement on young globular cluster observations with adaptive optics E. Moraux (IPAG)
09:35 Photometric and astrometric challenges and specifications for MAVIS F. Rigaut (ANU)
09:55 Astrometry of resolved stellar populations with MICADO at ELT D. Massari (U. Groningen)
10:15 An ELT view of R136 G. Fiorentino (INAF)
10:35 Break
11:00 Integrating the hardware and software design effort for MICADO at the ELT H. Buddelmeijer (Kapteyn Astronomical Institute)
11:20 A new software for photometry and astrometry in the AO era A. Marasco (U. Groningen)
11:40 AIROPA : A PSF Reconstruction program for NIRC2 P. Turri (UCB)
12:00 Lunch
Session 3 : Advanced image processing (Wednesday)
14:00 Invited Talk : Image processing for astronomical Adaptive-Optics corrected imaging L. Mugnier (ONERA)
14:35 PRIME : Psf Reconstruction and Identification for Multi-sources characterization Enhancement O. Beltramo-Martin (LAM)
14:55 Modelling the adaptive optics PSF : deconvolution of the asteroid Vesta R. JL Fetick (LAM)
15:15 SOWAT : Speckle Observations With Alleviated Turbulence F. Bosco (MPIA)
15:35 Needs of and benefits from PSF reconstruction on ELT instruments R. Wagner (JKT Linz)
15:55 Break
16:15 The PSF reconstruction plan for MICADO M. Rosensteiner (MPIA)
16:35 Numerical estimation and modeling of the wavefront error breakdown in adaptive optics F. Ferreira (LESIA)
16:55 Point Spread Function Reconstruction for Solar Adaptive Optics Systems L. Jolissaint (HEIGV)
17:15 Open discussion Day 2
Session 4 : High-contrast imaging (Thursday)
09:00 Invited Talk : High contrast imaging with adaptive optics A. Vigan (LAM)
09:35 Regime-switching model for direct exoplanet detection in ADI sequences C-H. Dahlqvist (U. Liege)
09:55 The single conjugate AO system of METIS M. Felt (MPIA)
10:15 Post-coronagraph image processing with HST and prospects for the future space telescopes É. Choquet (LAM)
10:35 Break
11:00 Using libraries of images with SPHERE J. Milli (ESO)
11:20 The wind driven halo in high-contrast imaging. F. Cantalloube (MPIA)
11:40 K-Stacker, an algorithm to hack the orbital parameters of planets hidden in the speckle residuals of high contrasts imaging and detect them H. Le Coroller (LAM)
12:20 Lunch
14:00 Open discussion day 3
14:45 Closing discussion
15:00 End of the Workshop



Speaker : F.-X. Dupé
Title : Learning to inverse : deep learning and inverse problems
Abstract:Inverse problems are ubiquitous when dealing with observation using complex systems. Thus a huge literature exists on how to solve such problems. Nowadays the most powerful methods ask for a good knowledge of the object of interest, leading to prior that embed expertise, physics and bias. One way to avoid these bias is to learn a good representation of the data with as less expertise as possible. This presentation will introduce some of these methods with a focus on neural networks and deep learning. Through two common problems we show how to learn to inverse them and expose the pro and cons of such approaches.

Speaker : R. Bacon.
Title : Get the best science with AO : lessons learned with MUSE
Abstract : The 2nd generation ESO MUSE integral field spectrograph has recently been commissioned with the GLAO (in 2017) and LTAO (in 2018) modes of the VLT adaptive optics facility. I will review the operation and performance of these systems and their science impact.

Speaker : N. Bouché.
Title : The role and limitations of the PSF in a forward model with GalPaK3D
Abstract : We will present a forward modeling approach to determine the morpho-kinematics parameters of distant galaxies directly from 3D data. This approach requires the knowledge of the PSF and in the area of current and planned AO instruments, we will discuss the advantages and limitations of this Bayesian 3D approach.

Speaker : T. Fusco
Title : PSF reconstruction for MUSE Wide Field Mode. Final on-sky performance and routine operations.
Abstract : In order to disentangle the instrument contribution from the intrinsic and tiny signature of the astrophysical signal in the observed data, one requires a precise knowledge of the instrumental spatial response (so-called Point Spread Function - PSF). The PSF delivered by AO systems has a complex shape, combining spatial, spectral and temporal variability. Although several approaches have been successfully developed for Single Conjugate AO over the past 20 years, there is no example of fully operational and astronomer-friendly algorithms. Moreover, the generalization of the SCAO approaches to the new generation of wide field laser –assisted AO system is quite complex and still in a development phase. On the other hand, in the zoology of AO system, Ground Layer AO represents an interesting playground for new approaches of PSF reconstruction. GLAO specificities and expected performance allows to completely re-thinking the very concept of PSF reconstruction. Hence, in the MUSE Wide Field Mode context, we have developed, in strong collaboration with MUSE scientists and GLAO developers, a dedicated tool (MUSE-PSFR) for a 3D estimation of the MUSE wide Filed Mode PSF. From the very beginning this tools has been specified and designed with well-defined scientific and operational constraints in order to be implemented in the MUSE pipeline and offered to the whole community. The MUSE-PSFR algorithm relies a simplified but yet very accurate model of the GLAO PSF shape which is adjusted (spatially and spectrally) using very few integrated atmospheric parameters derived from AOF (ESO AO Facility on UT4 which feeds MUSE with a GLAO corrected beam) telemetry data. After an extensive validation using full end-to-end simulations, MUSE-PSFR has been successfully tested on sky during more than one year of commissioning and science verification. Accuracy on PSF shape smaller than a few % have been regularly obtained. It is now used for science operation and in particular for more than 100 hours of the Hubble Deep Field GTO observations.
We will present the MUSE-PSFR concepts, its final implementation, its fine tuning, its current limitations and the latest on-sky performance obtained on 400 observations of a globular cluster obtained between July 2017 and August 2018. We will also give some perspectives concerning the upgrade of the model for the case of an LTAO system and its application to both the MUSE Narrow Field Mode and HARMONI on the ELT.

Speaker : L.Catala/G. Sivo
Title : Gemini North Adaptive Optics (GNAO) : an MCAO system for Gemini North
Abstract:Gemini Observatory has been awarded from the National Science Foundation a major fund to build a new state-of-the-art Multi Conjugate Adaptive Optics facility for Gemini North on Maunakea. The current baseline system will use three lasers each split in two to create an artificial constellation of six laser guide star to measure the distortions caused by the atmosphere. At least two deformable mirror conjugated to 0km and the main altitude layer above Maunakea will be used to correct these distortions. The facility will be designed to feed future instrumentation, initially a near infrared imager and potentially a visiting 4-arm multi object adaptive optics IFU spectrograph. 
In this presentation I will present the main characteristics of this exciting facility, its promises and its challenges. I will also present its conceptual design and results of trade studies conducted within the team and the Gemini Adaptive Optics Working Group. The expected first light is for October 2024.

Speaker : N. Thatte
Title : HARMONI science simulations with HSIM : Knowledge of the PSF
Abstract : Abstract : HARMONI is the first-light integral field spectrograph for the ELT, assisted by natural and Laser guide star adaptive optics. Operating over a broad wavelength range (from 500 nm to 2400 nm), HARMONI’s spatial resolution is strongly wavelength dependent, with peak Strehl ratios ranging from below 1% to 70%. We present the results of quantitative science simulations of a variety of science cases, carried out using the dedicated HARMONI simulator HSIM, with particular emphasis on the impact of knowledge of the PSF on the derived parameters from the mock observations. Improved computationally efficient methods for simulating the PSF will be presented, allowing non-axisymmetric PSF effects to be incorporated.

Author : A. Menduina
Title : NCPA calibration with Machine Learning in ELT-HARMONI
Abstract : In order to maximize the scientific output of the next generation of extremely large telescopes (E-ELT, TMT, GMT), advanced calibration techniques are needed to correct for instrument effects. A particularly challenging science case is the detection and characterization of Earth-like planets. This kind of observation requires contrast levels that can only be achieved by the joint effort of extreme adaptive optics, complex coronagraph designs, fine instrument calibration and sophisticated data post-processing. In the context of high-contrast imaging, the main limitation to planet detectability is the presence of quasi-static speckles that resemble a planetary signal. These speckles are usually caused by differential aberrations in the science-light path that cannot be sensed by the adaptive optics sensors and thus remain uncorrected. Although they are usually small in magnitude, correcting these aberrations would help push instruments closer to their limit capabilities. Here, we present a novel technique for the calibration of non-common path aberrations (NCPA) that relies on Machine Learning, in the context of instruments that contain image slicers (ELT-PCS, ELT-HARMONI). Estimating such aberrations so that they can be pre-compensated by the Deformable Mirror of the AO subsystems is key to enhancing the quality of the HARMONI science. Our method is capable of inferring the underlying NCPA directly from PSF images, with improvements of over 80% with respect to the initial RMS wavefront error. The neural network model we constructed is trained on thousands of PSF images simulated via Physical Optics Propagation with Zemax, so that it accounts for Fresnel diffraction effects at the image slicer. The model architecture can be extended to account for high order Zernike aberrations, while keeping the size of the training set manageable. In that context, multiple neural networks are trained independently to recognize different subsets of Zernike polynomials, and the overall wavefront error is corrected and estimated iteratively. In order to ensure the method converges, autoencoders (a special type of neural network that performs well in tasks such as denoising and dimensionality reduction) can be added to the architecture to facilitate the task of each independent network.
This method is lightweight, easy to implement and provides instantaneous NCPA calibration once the network has been trained, bypassing the need for iterative methods. We are confident that the calibration and pre-compensation of these aberrations with our machine learning method will enhance the capabilities of HARMONI across all science cases.

Speaker : M Puech
Title:MOSAIC : preparing phase B
Abstract : When combined with the huge collecting area of the ELT, MOSAIC will be the most effective and flexible Multi-Object Spectrograph (MOS) facility in the world, having both a high multiplex and a multi-Integral Field Unit (Multi-IFUs) capability. MOSAIC will provide R 5000 spectroscopy over the 450-1800 nm range, with three additional high-resolution bands (R 15000) targeting features of particular interest. It will combine three operational modes, providing the community with integrated-light observations of 100 sources on the sky (high-multiplex mode) in the optical or in the NIR, or integral field spectroscopy of 10 spatially-extended fields via deployable IFUs in the NIR.This will allow MOSAIC to be the fastest way to spectroscopically follow-up faint sources during the reionisation epoch, as well as in generating an inventory of both the dark matter and the cool to warm-hot gas phases in z=3.5 galactic halos. I will summarize the current status of MOSAIC with a particular focus on the MOAO requirements driven by the spatially-resolved kinematics (including realistic rotation curves) of galaxies at z 3-4.

SESSION 2 : Vis./NIR imaging

Speaker : E. Moraux
Title : Enhancement on young massive cluster observations with adaptive optics
Abstract : Young massive clusters are dense entities hosting a large number of high-mass stars as well as low mass stars, and are located at more than 1 kpc from the Sun in the Milky Way and even further away in other galaxies. As such the characterisation of their stellar population over a large mass interval remains challenging and requires high-angular resolution imaging.
In this presentation, I will highlight the benefits of adaptive optics on extremely large telescopes, that is necessary to beat crowding and resolve the stellar cluster population down to very low mass stars. This is of primordial importance if we want to measure the stellar IMF and test its universality in such massive environments. This will allow for the first time to study the IMF down to the substellar domain in far away young massive clusters in our galaxy as well as in the SMC/LMC.
Moreover, the very good astrometric precision resulting from the high spatial resolution will enable proper motion measurements with an accuracy of the order of a few km/s over a few years. We will thus be able to study the spatial and kinematics clustering of stars as well as the dynamical state of young massive clusters, and constrain their formation and evolution.

Speaker : F. Rigaut
Title : Photometric and astrometric challenges and specifications for MAVIS
Abstract : If it proceeds beyond phase A, MAVIS will deliver MCAO corrected low to moderate Strehl vivible images over a wide field of view. Although it considerably improves performance homogeneity, MCAO still leaves important fluctuations (Strehl/FWHM) and comes with its own set of limitations (static aberration correction, PSF structures). Although progress have been made in recent years, astrometry still need to be fully understood. I will try to expose, based on MAVIS pre-studies and the experience with GeMS, the challenges and limitations imposed by the multi-conjugate correction on the extraction of science parameters.

Speaker : D. Massari
Title : Astrometry of resolved stellar populations with MICADO@ELT
Abstract : Precise astrometry will be one of the major benefits of a diffraction limited Extremely Large Telescope (ELT). The goal of the Multi-AO Imaging Camera for Deep Observations (MICADO), one of the first light instruments for the ELT, is a relative astrometric precision of 50 microarcsec. By achieving such a requirement, a wealth of currently open science cases will be investigated that will lead to an unprecedented understanding of the formation and evolution of our Galaxy and its stellar populations. In this talk, I will present the first simulations of these science cases and the related results, highlighting successes and challenges that will need to be addressed by the time MICADO will be fully operational.

Speaker : G. Fiorentino
Title : An ELT view of R136
Abstract : A novel analysis of a star cluster (R136–like) based on ELT mock observations is presented. The first aim of this study is to assess the photometric and astrometric performance returned by an ELT observing such a crowded stellar field. Last aim of this analysis, but not least, is to test our ability in detecting an upper limit for an Intermediate Mass Black Hole (IMBH, 104M) at the center of this cluster. The astrometric accuracy reached is impressive, reaching few muas/year or km/sec. With these predicted performance, we are able to detect the IMBH located at the cluster center.

Speaker : H. Buddelmeijer
Title : Integrating the hardware and software design effort for MICADO at the ELT
Abstract : Complex systems like the Adaptive Optics assisted near-infrared imager MICADO at the ELT require an integrated design effort of the hardware and its calibration software to achieve to cutting edge astronomical performance. Traditionally, the instrument designers, software designers and designers of the astronomical science case have rather different methodologies and design tools and do not speak the same ‘language’. How to connect requirements, hardware specifications, models, simulations, documents, etc. in a consistent way without getting lost and causing too much overhead ? And how can such a connected, integrated design be flexible against inevitable changes during the design phase ? I’d like to share some ideas for tackling these questions for a MICADO subsystem : connecting the design of the imaging pipeline of MICADO and its data simulator, SimCADO. We explore a shared data model and formalized requirement tracing that together set the framework for specifying the calibration pipeline design and the validation of prototype code. The data model models both the data items that flow through the pipeline and their interdependencies and also the physical instrument items at a level sufficient for data calibration. Our goal is to align as closely as possible the data model underlying the processing software for real data with the data model underlying the production software for simulated data.

Speaker : Antonino Marasco
Title : A new software for photometry and astrometry in the AO era
Abstract : In the AO era, the intrinsic complexity and variability of the point spread function (PSF) pose severe challenges on the analysis of optical and NIR images. I will present preliminary results from a new astro-photometric software which we specifically designed to deal with spatially complex and variable PSFs. The software iteratively reconstructs a series of purely numerical PSFs from different regions of the image, interpolates them and fits them it to identified stellar sources, improving at each step both the PSF reconstruction and the source fitting quality. I will present the main advantages and disadvantages of this software and compare its performance to that of classical softwares (like DAOPHOT) on synthetic and real images.

Speaker : P. Turri
Title : AIROPA : A PSF Reconstruction program for NIRC2
Abstract : Many science cases of large telescopes with adaptive optics systems rely on accurate profile-fitting and one of the main challenges in reaching accurate astrometry and photometry is the measurement of the PSF shape, determined by atmospheric turbulence and instrumental aberrations. In recent years, there have been several efforts to advance PSF reconstruction (PSFR), a technique that can predict the PSF on instruments using adaptive optics. This strategy will become more common in the next decades, with uses on NIRC2 at Keck and IRIS at TMT. But while it has been demonstrated to work on sky in simple tests, it has not been used yet for scientific observations.
At the University of California, we are developing AIROPA, a PSFR and profile-fitting software for NIRC2 based on StarFinder. The atmospheric component of the PSF is modeled from MASS and DIMM data taken simultaneously to the NIRC2 observation. Static instrumental aberrations are measured ahead of time with phase diversity. Finally, the residual PSF structure that is not accounted by these two methods is extracted from the images of stars in the NIRC2 frame. I will explain the approach to PSFR taken by AIROPA. I will demonstrate the expected astrometric and photometric performance in simulations when compared to classical methods of PSF extraction. Finally, I will discuss the challenges faced in porting this technique on-sky.

SESSION 3 : Image processing

Speaker : L. Mugnier
Title : Image processing for astronomical Adaptive-Optics corrected imaging
Abstract : High angular resolution imaging from the ground has spurred a lot of research in image processing methods for several decades, first in uncorrected then in Adaptive Optics (AO) corrected imaging. This talk will give a short overview
of the problems tackled and of the advances made in image processing for
astronomical AO-corrected imaging. In several imaging scenarii, a first problem is to register and co-add a series of "short" exposures into a long exposure, which will then be deconvolved. One such scenario is the imaging of faint objects in the IR,
where the sky background overwhelms the signal. Another scenario is imaging
with a multi-conjugate AO system suffering from a time-varying distorsion. A central topic is then the deconvolution of long-exposure isoplanatic images. I’ll recall the Bayesian framework, in which most existing methods can be cast, the possible noise models, and various priors that have been used in the literature. Then I’ll address the difficult and ubiquitous question of blind or myopic deconvolution, i.e. of deconvolution with an imperfectly known PSF. I’ll examine constraints, both on the object and on the PSF, that have been used to render this problem less ill-posed, and I’ll show that most methods boil down to the joint estimation of PSF and object. I’ll then go over recent approaches such as marginalized estimation or MCMC estimation that benefit from appealing theoretical properties. Finally, I’ll touch upon some of the many avenues that are being explored or promising for recent and future instruments : multi-spectral deconvolution, wide-field anisoplanatic image restoration, multi-frame short-exposure AO-corrected deconvolution, etc.

Speaker : O. Beltramo-Martin
Title : PRIME : Psf Reconstruction and Identification for Multiple sources characterization Enhancement
Abstract : Ground-based astronomical observations are boosted thanks to adaptive optics (AO) and post-processing techniques but face spatial and time variations of the Point spread function (PSF), which may limit the extraction of astrophysical estimates, such as photometry and astrometry. To mitigate the potential PSF indetermination, we investigate a new concept of Psf Reconstruction and Identification for Multi-sources characterization Enhancement (PRIME) that handles conjointly the science image and the AO telemetry to improve the estimates accuracy. We present in this paper a validation of the different ingredients that constitutes PRIME, which are the reconstructed PSF parametrization, the PSF calibration and the myopic estimation of photometry and astrometry. We show that the PSF calibration achieves 0.4% and 0.8 mas of accuracy on respectively the Strehl-ratio and the PSF full width at half maximum on Keck II telescope NIRC2 images and permits to diagnose the AO error breakdown and atmospheric parameters. We also validate the myopic estimation process on tight binaries by comparing to a blind approach based on the extracted PSF, which estimates photometry and astrometry at 0.04 mag and 50μas accuracy and 0.005 mag and 100μas of precision on a 14 mag object.

Speaker : R. JL Fetick
Title:Modelling the adaptive optics PSF : deconvolution of the asteroid (4)Vesta
Abstract : Adaptive optics (AO) systems partially correct the damaging effects of the atmospheric turbulence on imaging resolution. However the imperfect AO correction produces blurring and leads to a very peculiar shape of the PSF. A simple analytical model accurately reproducing the AO-corrected PSF shape would represent a valuable input for any post-processing methods, particularly for deconvolution, when no empirical PSFs can be derived from the images. In the literature, various parametric mathematical functions are used to try to estimate at best the PSF’s turbulent halo. Nevertheless there is hardly a physical meaning of these parameters. Based on the image formation theory, we developed a PSF model from a parameterization of the aberrant phase power spectral density (PSD). This model is aimed to be more physical, particularly we can correlate the turbulent halo shape with the Fried parameter r0 for the turbulence strength. This model is built to match the following requirements : versatility, robustness, accuracy, simplicity, and physical parameters. We successfully matched PSF from different AO systems, including the VLT/SPHERE/ZIMPOL and the integral field spectrometer VLT/MUSE. Moreover we show that parameterized PSF are well suited for images deconvolution. We used the MISTRAL deconvolution algorithm with parametric PSFs on ZIMPOL images of the (4)Vesta asteroid. Since the NASA Dawn in-situ mission gives access to the asteroid ground truth, we can then quantify precisely the achievable resolution from Earth based telescopes coupled to deconvolution post-processing. This model will be used for ELT instruments, such as HARMONI. Additionally, parametric PSF will be inserted into the MISTRAL myopic deconvolution algorithm, for efficient estimation of both the observed object and the instrument PSF. Parameterization of the PSF reduces the number of degrees of freedom and possible degeneracies into minimization algorithms.

Speaker : F. Bosco
Title : SOWAT : Speckle Observations With Alleviated Turbulence
Abstract : Adaptive optics (AO) systems and (advanced) speckle imaging techniques are indispensable tools when it comes to ground-based high-precision astrometry. In this talk, I present our analysis of the benefits of combining both techniques, i.e. by applying image reconstruction on AO corrected short-exposure images. Therefore we simulated speckle clouds of 8m-class telescopes with and without AO corrections and created synthetic observations. We applied the holographic image reconstruction technique to the obtained observations and found that (i) the residual wave fronts decorrelate slower and to a lower limit when AO systems are used, (ii) the same reference stars yield a better reconstruction, and (iii) we achieve a similar image quality when using fainter reference stars. These results suggest that holographic imaging of speckle observations is feasible with longer integration times and fainter reference stars, obtaining diffraction-limited observations from basic ground-layer AO systems that are less restricted than complex AO systems.

Speaker : R. Wagner
Title : Needs of and benefits from PSF reconstruction on ELT instruments
Abstract : The upcoming generation of Extremely Large Telescopes (ELT), with mirror diameters of up to 40 m, will heavily use Adaptive Optics (AO) systems to correct for the impact of turbulent atmosphere. Even with AO systems, such as Single Conjugate Adaptive Optics (SCAO), the quality of astronomical images still is degraded due to the time delay stemming from the wavefront sensor (WFS) integration time and adjustment of the deformable mirror(s) (DM). This results in a blur which can be mathematically described by a convolution of the original image with the point spread function (PSF). The PSF of an astronomical image varies with the position in the observed field, which is a crucial aspect in observations on ELTs. We present the developments to make PSF reconstruction methods ready for the use of Pyramid WFS and provide estimates for off-axis PSFs in SCAO systems. We discuss the steps to bring PSF reconstruction to the telescope at first light, including necessary hardware and calibrations. In the same framework, as one possible way of image improvement, we enhance the quality of the observed images and reconstructed PSFs simultaneously by using so-called blind deconvolution methods. The reconstructed PSFs can be used as baseline for deriving astronomical metrics whenever a deconvolution scheme is not feasible.

Speaker : M. Rosensteiner
Title : The PSF reconstruction plan for MICADO
Abstract : MICADO is one of the first-light instruments for the ELT. It is a NIR imager and spectrograph taking advantage of the capabilities of two AO modes, a SCAO module and the MCAO instrument MAORY. To support the astronomer in the evaluation of scientific images, it will feature the possibility to reconstruct the AO-corrected PSF. We give an overview on the ongoing development of the PSF reconstruction system.

Speaker : F. Ferreira
Title : Numerical estimation and modeling of the wavefront error breakdown in adaptive optics
Abstract : For ground-based telescopes, Adaptive Optics (AO) systems aim to correct the wavefront disturbances due to atmospheric turbulence.The Point Spread Function (PSF) is one of the metrics of the AO system correction performance when compared to the diffraction limited one. Estimating the AO corrected PSF is important for image inversion which requires accurate estimation of the PSF over the scienti c field. This estimation relies on the knowledge of the AO system error budget. Establishing the various contributions of this error budget is an issue because of the propagation process of errors through the AO loop filtering. We have developed a model for SCAO system residual error breakdown which includes temporal error, anisoplanatism, aliasing, noise and tting terms. Thanks to GPU acceleration, it leads to PSF estimation at ELT scale in half a minute.

Speaker : L. Jolissaint.
Title : Point Spread Function Reconstruction for Solar Adaptive Optics Systems
Abstract : A network for the development of solar adaptive optics for the future European Solar Telescope (EST) has been set up in Europe. In Switzerland, we are responsible for the development of an algorithm for the reconstruction of the AO system’s PSF (PSF-R). In the case of solar AO, there is absolutely no point source in the field-of-view that can be used to estimate the PSF, therefore the PSF has to be built from telemetry and a priori knowledge. In this talk, we will explain what is specific to the case of solar AO PSF-R and how we are recycling what we have learnt from night time experiment on the W. M. Keck telescope. First results using the GREGOR telescope AO system data will be shown.

SESSION 4 : High-contrast imaging

Speaker : A. Vigan
Title : High-contrast imaging with adaptive optics
Abstract : The detection and characterization of exoplanets is one of the major goals of modern astrophysics. Since the discovery of the first exoplanet around a solar-type star in 1995, this field has developed exponentially thanks to the diversity of exoplanet detection techniques. Among these techniques, direct imaging enables to measure the intrinsic or reflected light of exoplanets, which provides a direct access to the composition of their atmospheres. It is also the only technique that can probe close circumstellar environments to look for protoplanetary and debris disks. However, direct imaging has strong instrumental implications for ground-based telescopes. It requires dedicated instruments on large telescopes, equipped with powerful adaptive optics systems, efficient coronagraphs and high-quality imaging or spectroscopic sub-systems. In addition, the use of clever observing strategies, data analysis techniques and target selections is another fundamental step to reach contrasts high enough to detect sub-stellar companions and study circumstellar environments. In this presentation I will review these key elements and how their improvements have enabled new astrophysical developments over the years.

Speaker : C-H. Dahlqvist
Title : Regime-switching model for direct exoplanet detection in ADI sequences
Abstract :Beyond the choice of wavefront control systems or coronographs, advanced data processing methods play a crucial role in disentangling potential planetary signals from bright quasi-static speckles. Among these methods, angular differential imaging (ADI) proved to be a promising research avenue considering the many ADI based techniques that have been proposed recently for high contrast imaging. Inspired by Statistics and Econometrics, we proposed in this paper a new detection algorithm deriving from the regime-switching model first proposed by Hamilton(1988). The proposed model is very versatile as it allows the use of treated datasets provided by different ADI based techniques separately or together to provide a single detection map. The temporal structure of the different datesets is used for the detection as the model is fed with aligned treated frames. The algorithm provides a detection probability map by considering for each annulus two possible regimes, the first one representing the background noise and the second one being the planetary signal.

Speaker : M. Felt
Title : The single conjugate AO system of METIS
Abstract : METIS is one of the three first-light instruments for the ELT, and a complex one at that. METIS comprises three focal plane instruments, 2 imager-spectrographs for the LM and NQ bands respectively, plus an LM-band integral field spectrograph. One of the key science cases for METIS is the imaging of exo-planets, and it is thus fully equipped with a suite of coronagraphs, and a fast, high-order AO wavefront sensing system. Similar to SPHERE, METIS is "blessed" with a requirement on achievable contrast, which in turn requires a complex set of careful analyses of the impact of each design decision, error budget contribution, and possible failure condition on both Strehl and contrast performance. I will present the current design status and timeline of METIS, summarize the system characteristics, and present the latest of our systemic analysis simulations.

Speaker : É. Choquet
Title : Post-coronagraph image processing with HST and prospects for the future space telescopes
Abstract : To reach their science goals of imaging faint extrasolar systems, high-contrast imagers rely heavily on aggressive image processing technics. Their purpose is to subtract the coronagraphic PSF of the star down to the highest contrasts while minimizing their effect on the circumstellar scene. Although on a very stable orbit, the Hubble Space Telescope still suffers from thermal variations that constantly distort its coronagraphic PSF and limit the efficiency of classical PSF subtraction technics. I will present results obtained by reprocessing the HST-NICMOS archive with state-of-the-art post-processing techniques, and discuss the prospects of image processing for the future space telescopes WFIRST and LUVOIR/Habex, which will be equipped with active wavefront control systems.

Speaker : J. Milli
Title : Using libraries of images with SPHERE
Abstract : In high-contrast imaging, the challenge consists in estimating and subtracting the coronagraphic image of the star to reveal the circumstellar environment (planets or disks). Recent revisits of archival data from space-based instruments such as HST/NICMOS have shown a significant improvement in using a large library of images combined with dedicated post-processing techniques to reconstruct this coronagraphic image. We show here the application of this technique for ground-based AO instruments. Based on a survey of 55 disk-host targets observed with SPHERE, we demonstrate that this technique can reach contrasts at short separation deeper than standard techniques. We also highlight the future challenges to develop this technique to larger surveys.

Speaker : F. Cantalloube.
Title : The wind driven halo in high-contratst imaging.
Abstract : The wind driven halo observed in the images obtained from the latest generation of high contrast instruments (GPI, SPHERE, SCExAO…) is one of the limiting effect which prevents reaching the best contrast, in particular for extended features such as circumstellar disks for which a high pass filtering is not possible. In this talk, I’ll describe this feature and show its correlation with atmospheric parameters and why it remains in the images after the current post-processing techniques. I’ll then show potential mitigation strategies to get rid of it by post-processing.

Speaker : H. Le Coroller
Title : K-Stacker, an algorithm to hack the orbital parameters of planets hidden in the speckle residuals of high contrasts imaging and detect them
Abstract : Only a few new exoplanets have been found after more than ten years of observations with high contrast imaging instruments (NaCO, SPHERE, GPI, etc.). In this context, each new exoplanet detection brings very important constraints to better understand the formation mechanisms, and the physical properties of these young Jupiter detected by direct imaging. Notably, to probe the area of planets formed by core-accretion, we need to improve the contrast limit at small separation, near the coronagraphic mask. We will present a new algorithm and observing strategy that could improve the detection limit in the A.O. corrected area, up to a factor of 5 - 10. It consists in combining the high contrast images recorded during different nights, accounting for the orbital motion of the putative planet that we are looking for. Even if nothing is detected in every individual observation, we show (Le Coroller OHP2015 ; Nowak et al. A&A 2018) that an optimization algorithm (K-Stacker) can align the planet images according to keplerian motions (ex : 3-50 images taken over a long period of several months or years), increase the signal-to-noise ratio, and detect the planet otherwise unreachable. We will present the instrumental constraints (TN and centering accuracy) required to be able to use K-Stacker in the context of future instruments (SPHERE-Upgrade, HARMONI … ELT, etc.) 

Local Information

The workshop will be held at Laboratoire d’Astrophysique de Marseille.

Postal adress : 38 street F. Joliot-Curie, 13013 Marseille.
How to come to LAM : Take Metro 1 (blue line) to terminus "La Rose" and then take the bus B3B to stop "École Centrale Marseille". It takes around 30 mn from downtown to come.

On Tuesday 26th evening, a social event is organised at "Restaurant La Nautique" located at 20 QUAI DE RIVE NEUVE - 13007 MARSEILLE.

Links to past meetings


Thierry FUSCO
Arthur VIGAN


© LAM - Laboratoire d’Astrophysique de Marseille

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