Non-modulated pyramid wavefront sensor: Why, how and when to use it to sense and correct atmospheric turbulence

Context. The diffusion of adaptive optics systems in astronomical instrumentation for large ground based telescopes is rapidly increasing and the pyramid wavefront sensor is replacing the Shack-Hartmann as standard solution for single conjugate adaptive optics systems. The pyramid wavefront sensor is typically used with a tip/tilt modulation to increase the linearity range of the sensor, but the non-modulated case is interesting because it maximizes the sensor sensitivity. The latter case is generally avoided for the reduced linearity range that prevents robust operation in the presence of atmospheric turbulence. Aims. We aim to solve part of the issues of the non-modulated pyramid wavefront sensor by reducing the model error in the interaction matrix. We linearize the sensor response in the working conditions without extending the sensor linearity range. Methods. We introduce a new calibration approach to model the response of pyramid wave front sensor in partial correction, where the working conditions in the presence of residual turbulence is considered. Results. We show how in simulations, through the new calibration approach, the pyramid wave front sensor without modulation can be used to sense and correct atmospheric turbulence and when this case is preferable to the modulated case.Comment: 12 pages with 18 figures; accepted for publication in A&

Overview of AO calibration strategies in the ELT context

The scientific potential of the ELT will rely on the performance of its AO systems that will require to be perfectly calibrated before and during the operations. The actual design of the ELT will provide a constraining environment for the calibration and new strategies have to be developed to overcome these constraints. This will be particularly true concerning the Interaction Matrix of the system with no calibration source upward M4 and moving elements in the telescope. After a brief presentation of the ELT specificities for the calibration, this communication focuses on the different strategies that have already been developed to get/measure the Interaction Matrix of the system, either based on synthetic models or using on-sky measurements. First tests of these methods have been done using numerical simulations for a simple AO system and a proposition for a calibration strategy of the ELT will be presented

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Stratégies d’étalonnages innovantes pour grands télescopes adaptatifs avec analyseurs de front d’onde pyramide

The new generation of Extremely Large Telescopes (ELT) will provide an optical resolution never achieved before for ground-based observation. However, in order to fully benefit from the potential of these telescopes, the scientific instruments will rely on complex Adaptive Optics Systems (AO) to correct for the optical aberrations due to the atmospheric turbulence. These AO instruments will all include Pyramid Wave-Front Sensor (PWFS) in their design as these WFS provide a gain in sensitivity with respect to the historical Shack-Hartmann WFS (SH). The cost of this gain in sensitivity comes with a higher operational complexity as the sensor exhibits a modal linearity and sensitivity that depends on both the seeing conditions and level of AO correction itself, the so-called optical gains of the PWFS. Coupled to this very first technical challenge, the future ELT will provide a constrained environment for the AO calibration with a large number of degrees of freedom, that will have to be calibrated often without any external calibration source and unprecedented distances between Deformable Mirror (DM) and AO instruments. This will induce differential motions and thus opto-mechanical conjugation errors between WFS and DM. Regular evolution of these so-called mis-registrations are then to be expected during the observations. They have to be monitored and compensated as they will highly affect the AO performance or lead to loop instability that will jeopardize the scientific observations. To address these operational constraints, we propose to consider a pseudo synthetic approach where calibration data are generated from a synthetic model, identifying the model parameters from experimental inputs. Such strategy is already used at the Adaptive Optics Facility working with SH-WFS. For PWFS, synthetic-based calibration have already been performed on several existing systems but a tracking of the mis-registration parameters during the operation is still to be investigated.As part of my PhD studies, I first developed a pseudo-synthetic model of the AO system of the Large Binocular Telescope that included the modelling of a PWFS and Adaptive Secondary Mirror. The purpose of this model was to generate a pseudo synthetic Interaction Matrix that could be used on the real system and identify the key-ingredients to efficiently model the PWFS. The model has been experimentally validated at the telescope and provided the same level of AO performances as a measured interaction matrix, demonstrating the high accuracy of the model. For this experiment, to tune the parameters of the model, we had access to a full interaction matrix measured at the telescope which will not be the case of the future ELT. The second part of my PhD was focused on optimizing the identification of the mis-registration parameters to allow a regular tracking of the parameters during the operation. We identified two strategies to provide an online tracking of the parameter. The first one is invasive and consists in dithering well selected signals with a low amplitude on the DM during the operations. This method appears to be robust to the different observing conditions and we demonstrated that the perturbation can be reduced to a few signals only, selected to maximize the sensitivity to the mis-registrations. This method has to be applied with the constraints of minimizing the impact on the scientific path that has to be carefully evaluated.Another strategy consists in accumulating enough telemetry data to retrieve a noisy interaction matrix that is used to give an estimation of the mis-registration parameters. This non invasive method appears to be attractive as no perturbation on the scientific path is required. The purpose of our research was to understand the physics that underpin the estimation of this noisy interaction matrix to identify the domain of validity of the method depending on the observing conditions, especially when considering its application with a PWFS.Les futurs Télescopes Géants (ELT) auront une résolution jamais atteinte avec des télescopes terrestres. Cependant, pour exploiter pleinement leur potentiel scientifique, il sera nécessaire de les équiper de systèmes d’Optique Adaptative (AO) complexes pour corriger les aberrations optiques dues à la turbulence atmosphérique. Ces instruments possèderont tous un Analyseurs de Surface d’Onde (ASO) de type Pyramide (PWFS) qui permet d’obtenir un gain en sensibilité vis-à-vis de l’ASO Shack-Hartmann (SH). Ce gain a toutefois un prix en terme de complexité opérationnelle. Les PWFS présentent en effet une linéarité et une sensibilité modales qui dépendent à la fois des conditions d’observations et du niveau de correction de la boucle d’AO elle-même.Le design des futurs ELT imposera de nombreuses contraintes pour l’étalonnage des système d’OA avec un grand nombre de degrés de libertés à étalonner, souvent sans source d’étalonnage externe, et avec une très grande distance séparant le miroir déformable (DM) et l'ASO. Cette distance provoquera l’apparition d’erreurs de conjugaison opto-mécanique entre ASO et DM: les mis-registrations. Ces mis-registrations évolueront régulièrement pendant les observations ce qui impactera les performances du système d’OA ou provoquer des instabilités de la boucle. Un système de suivi et de compensation de ces mis-registrations sera nécessaire pour ne pas compromettre le bon déroulement des observations scientifiques.Pour répondre à ces problématiques, nous proposons de considérer une approche pseudo synthétique où les données d’étalonnages sont générées depuis un modèle qui requiert l’identification de quelques paramètres grâce à des données expérimentales. De telles stratégies ont déjà été développées pour des ASO de type SH. Dans le cas des PWFS, des étalonnages basés sur des modèles synthétiques ont déjà été développés mais il reste à étudier la possibilité de faire un suivi de ces paramètres durant les observations. Durant la première partie de ma thèse, j’ai développé un modèle Pseudo Synthétique des OA du Large Binocular Telescope (LBT) qui incluait la modélisation d’un PWFS et d’un miroir secondaire adaptatif. Le but de ce travail était de générer une matrice d’interaction pseudo synthétique qui puisse fonctionner au télescope et d’identifier les éléments clés pour effectuer une modélisation précise du PWFS. Ce modèle a été validé expérimentalement au LBT, obtenant le même niveau de performance qu’une matrice d’interaction mesurée au télescope ce qui a démontré la haute précision du modèle. Dans le cadre de cette expérience, nous avions accès à une matrice d’interaction mesurée au télescope pour paramétrer le modèle, ce qui ne sera pas le cas des futures ELT.La seconde partie de ma thèse était donc orientée pour optimiser les stratégies d’identifications de ces paramètres et ainsi permettre un suivi durant les observations. Une première stratégie, dite invasive, consiste à appliquer des perturbations à faible amplitude sur le DM pendant les opérations. Cette méthode apparait comme robuste aux différentes conditions d’observations et nous avons démontré que la perturbation appliquée sur le miroir pouvait être réduite à quelques signaux bien choisis pour maximiser la sensibilité aux mis-registrations. L’application de cette méthode est cependant soumise à la contrainte de minimiser l’impact sur les observations scientifiques. Une autre stratégie consiste à accumuler suffisamment de données de la boucle pour retrouver une estimation bruitée de la matrice d’interaction qui est utilisée pour estimer les paramètres du modèle. Cette méthode, non invasive, apparaît comme séduisante car elle n’a aucun impact sur la voie scientifique. Le but de notre recherche était de comprendre la physique derrière l’estimation de cette matrice d’interaction bruitée pour identifier le domaine de validité de la méthode en fonction des conditions d’observations, en particulier en considérant son application avec le PWFS

Including the pyramid optical gains into analytical models

International audienceFourier-filtering wavefront sensors (WFS), such as the pyramid of Zernike WFS, are shown to be highly sensitive.They are becoming the baseline for future adaptive optics (AO) systems for astronomy. The next generationExtremely Large Telescopes (ELTs) will be equipped with such sensitive WFS. However the main drawback ofthese sensors is a quick loss of linearity when subject to strong turbulence residuals.Two major methods can be identified to simulate the AO point-spread-function (PSF): the end-to-endsimulation and the analytical model. The first one propagates random samples of phase screens through a fullysimulated AO loop, it can thus reproduce fine spatial and temporal effects, inlcuding the WFS non linearities.The second method is based on analytical formulas that provide a quick simulation with a good understanding ofthe AO system (separation of the AO error terms) but require a linear response of the system.We develop here a method to include the non linearities of the WFS into analytical formulas. It consequentlyimproves the accuracy of the simulation and enables to describe with good accuracy Fourier-filtering WFS. We testour method against end-to-end simulations, and derive possible applications for AO system design or performanceestimation

OOPAO: Object Oriented Python Adaptive Optics

International audienceOOPAO: Object Oriented Python Adaptive Optic

PAPYRUS at OHP: Predictive control with reinforcement learning for improved performance

International audiencePAPYRUS at OHP: Predictive control with reinforcement learning for improved performanc

Study of the LIFT focal-plane wavefront sensor for GALACSI NFM

International audienc

Toward the full control of NCPA with the pyramid wavefront sensor: mastering the optical gains

International audienceThe pyramid wavefront sensor is an asset for an AO system thanks to its sensitivity. However, because itsa nonlinear sensor it comes with operational challenges. A convolutional method and a gain sensing cameraallow to track the optical gains, which encode the sensitivity variations due to the nonlinearities. Tracking andcompensating the optical gains is necessary to perform extreme adaptive optics and to operate the pyramidoff-zero to compensate for the NCPA.This study focuses on the reliability of this method. A numerical twinof the bench PAPYRUS, developed for this study, shows a improvement of the performance by a factor 2.7 onthe Strehl Ratio when compensating for the optical gains. The convolutional method is implemented for thePAPYRUS bench, allowing the first on-sky tracking of optical gains. The next main steps are to compensate forthe optical gains in real-time, then to offset the pyramid in order to optimise fiber-injection, to compensate forNCPA and to provide AO generated dark hole for high-contrast imaging

Toward the full control of NCPA with the pyramid wavefront sensor: mastering the optical gains

International audienceThe pyramid wavefront sensor is an asset for an AO system thanks to its sensitivity. However, because itsa nonlinear sensor it comes with operational challenges. A convolutional method and a gain sensing cameraallow to track the optical gains, which encode the sensitivity variations due to the nonlinearities. Tracking andcompensating the optical gains is necessary to perform extreme adaptive optics and to operate the pyramidoff-zero to compensate for the NCPA.This study focuses on the reliability of this method. A numerical twinof the bench PAPYRUS, developed for this study, shows a improvement of the performance by a factor 2.7 onthe Strehl Ratio when compensating for the optical gains. The convolutional method is implemented for thePAPYRUS bench, allowing the first on-sky tracking of optical gains. The next main steps are to compensate forthe optical gains in real-time, then to offset the pyramid in order to optimise fiber-injection, to compensate forNCPA and to provide AO generated dark hole for high-contrast imaging