This PDF file contains the front matter associated with SPIE Proceedings Volume 13097, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

The facility adaptive optics of the Subaru Telescope AO188 recently received some long-awaited upgrades: a new 3224-actuator deformable mirror (DM) from ALPAO (hence the name change to AO3000 or AO3k), an upgraded GPU-based real-time computer, a visible nonlinear curvature wavefront sensor and a near-infrared wavefront sensor (NIR WFS), closing the loop at up to 2kHz. The wavefront sensors were added in 2023, while the DM will be installed at the beginning of 2024. With these new features, AO3k will provide extreme-AO level of correction to all the instruments on the IR Nasmyth platform: The NIR-MIR camera and spectrograph IRCS, the high-resolution Doppler spectrograph IRD, and the high-contrast instrument SCExAO. AO3k will also support laser tomography (LTAO), delivering high Strehl ratio imaging with large sky coverage. The NIR WFS, using part of the light from y- to H-band, is dramatically increasing the number of reachable targets for high-contrast imaging (HCI), for exoplanets characterization, as well as AGNs or the galactic center. It has two modes that can be used to drive the new DM: A double roof-prism pyramid WFS, and a focal plane WFS for faint targets. The high Strehl will especially benefit SCExAO for high-contrast imaging, both in infrared and visible. The second stage extreme AO will no longer have to chase large residual atmospheric turbulence, and will focus on truly high-contrast techniques to create and stabilize dark holes, as well as coherent differential imaging techniques. We will finally be able to leverage the several high performance coronagraphs tested in SCExAO, even in the visible. AO3k will answer crucial questions as a precursor for future adaptive optics systems for ELTs, especially as a technology demonstrator for the HCI Planetary Systems Imager on the Thirty Meter Telescope. A lot of questions are still unanswered on the on-sky behavior of high actuator counts DMs, NIR wavefront sensing, the effect of rolling shutters or persistence. We present here the first on-sky results of AO3k, before the system gets fully offered to the observers in the second half of 2024. These results give us some insight on the great scientific results we hope to achieve in the future.

As a part of the adaptive optics (AO) upgrade at the Subaru Telescope, we started developing a non-linear curvature wavefront sensor (nlCWFS), which is a new visible WFS for the upgraded facility AO system of the Subaru Telescope. We have successfully installed the nlCWFS on the Subaru Telescope following our previous lab demonstrations. This talk presents the commissioning of the nlCWFS. We first present the installation process of the nlCWFS and closed-loop performance with an internal source. We also highlight the recent on-sky results with the nlCWFS. We conclude by comparing the AO performance before and after the AO upgrade and with future works for implementing the non-linear wavefront reconstruction algorithms.

The Research, Experiment and Validation of adaptive Optics on a Legacy Telescope (REVOLT) project is an on-sky AO technology research platform which was commissioned at the Dominion Astrophysical Observatory’s (DAO) 1.2m telescope in Victoria, Canada in June 2022. The goal of the project is to provide a flexible and expandable AO system to test a wide variety of technologies and control strategies with rapid deployment to sky. To date, REVOLT has enabled the first on-sky use of the Herzberg Extensible Adaptive Realtime Toolkit (HEART), a realtime controller software package developed at the National Research Council of Canada’s Herzberg Astronomy and Astrophysics (NRC-HAA) research centre, slated to be deployed on multiple future AO instruments. REVOLT has provided the first on-sky demonstration of First Light Imaging’s C-Blue-One CMOS camera as a Shack-Hartmann Wavefront Sensor (SH-WFS), and demonstrated injection of the science PSF into a single mode fiber to feed experimental Spectral Correlation Sensor technology being developed to detect gas signatures in planetary atmospheres. Since its initial commissioning as a Single Conjugate AO (SCAO) system, an open loop arm, the GIRMOS Open Loop Demonstration (GOLD) arm, has been added to test OL calibration and control, and a Pyramid WFS (PWFS) arm has been added with the goal first of testing the Gemini Planet Imager 2 (GPI-2) HEART pipeline, as well as provide an on going test platform for PWFS research. This paper provides a full description of the current REVOLT system, summarizes the performance of each experiment conducted to date, highlights future plans and openly invites proposals for collaboration from the AO community.

REVOLT (Research, Experiment and Validation of Adaptive Optics with a Legacy Telescope)—the local adaptive optics (AO) system at National Research Council’s Herzberg Astronomy and Astrophysics Research Centre (NRC-Herzberg)—is an on-sky testbed for a variety of new technologies and algorithms, including the Herzberg Extensible Adaptive optics Real-time Toolkit (HEART). In this paper, we show first light results from a recent expansion of REVOLT to include a second closed-loop wavefront sensing path using a pyramid wavefront sensor (PWFS), REVOLT-COPPER (Canadian On-sky Platform for PWFS Experimental Research). We show successful operation of a modulated PWFS using the Gemini Planet Imager 2 (GPI2) HEART pipeline where we use a PWFS pixels-to-modes reconstructor, bypassing the need to calculate PWFS slopes first. We also present analysis of REVOLT-COPPER’s performance and discuss the on-going research and development effort at NRC-Herzberg.

Extreme adaptive optics (ExAO) systems are optimized for high-contrast imaging and coronagraphy. ExAO systems are currently limited to wavefront sensing using a bright natural guide star (NGS) due to the need for high precision wavefront control. Recent advances in sodium laser guide star (LGS) technology such as high power, efficient laser sources and pre-compensation of the laser uplink overcome previous limitations in LGS technology, opening up the potential for LGS technology to improve ExAO system performance with dim targets. The LAser guide Star Sensor Integrated Extreme adaptive optics (LASSIE) project at the Starfire Optical Range will explore the trade space in beacon size, brightness, coherence, and wavefront sensor design to preform path-finding research on the potential performance of an uplink-corrected LGS-ExAO system. In this presentation we will discuss the current progress of the LASSIE project.

The imaging search for exoplanets is mainly limited by quasi-static speckle noise that have lifetimes between milliseconds and hours. Attempts to remove this noise using post-processing by building a point spread function (PSF) model from diversity in time, wavelength, and so-forth are limited to a small improvement due to the evolution of the noise along these same axes. The Calibration 2 (CAL2) system, being built by an international team, is a National Research Council of Canada (NRC) funded facility-class focal plane wavefront sensor for the Gemini Planet Imager 2 (GPI2) upgrade. The project consists of a complete rebuild of the GPI calibration (CAL) system. Based on the self-coherent camera concept and the FAST focal plane mask, a fraction of the near-infrared (NIR) science bandpass is extracted using a new dichroic wheel to perform focal plane wavefront sensing, with the goal to do science while also improving the contrast for the GPI2 IFS, up to a factor of 100x on bright stars. The project is at the final design review stage, and construction is expected to start summer/fall 2024, with assembly late fall 2024, and shipping to the Gemini North observatory middle of 2025.

MagAO-X is the coronagraphic extreme adaptive optics system for the 6.5m Magellan Clay Telescope. We report the results of commissioning the first phase of MagAO-X. Components now available for routine observations include: the >2kHz high-order control loop consisting of a 97 actuator woofer deformable mirror (DM), a 2040 actuator tweeter DM, and a modulated pyramid wavefront sensor (WFS); classical Lyot coronagraphs with integrated low-order (LO) WFS and control using a third 97-actuator non-common path correcting (NCPC) DM; broad band imaging in g, r, i, and z filters with two EMCCDs; simultaneous differential imaging in Hα; and integral field spectroscopy with the VIS-X module. Early science results include the discovery of an Hα jet, images of accreting protoplanets at Hα, images of young extrasolar giant planets in the optical, discovery of new white dwarf companions, resolved images of evolved stars, and high-contrast images of circumstellar disks in scattered light in g-band (500nm). We have commenced an upgrade program, called “Phase II”, to enable high-contrast observations at the smallest inner working angles possible. These upgrades include a new 952 actuator NCPC DM to enable coronagraphic wavefront control; phase induced amplitude apodization coronagraphs; new fast cameras for LOWFS and Lyot-LOWFS; and real-time computer upgrades. We will report the status of these upgrades and results of first on-sky testing in March-May 2024.

SHARK-VIS, the Large Binocular Telescope (LBT) optical high-contrast imager, had its first light in October 2023. Thanks to the high performance of the refurbished LBT adaptive optics system SOUL, SHARK-VIS extends the capabilities of one arm of the LBT telescope down to 400nm, delivering images with a spatial resolution in the order of 20 mas, which in the infrared bands will be achieved only by future Extremely Large Telescopes. This document reports the instrument’s preliminary performance on-sky, which confirms that SHARK-VIS is ready for its main science applications. Specifically, we will show that the instrument is able to provide views of minor bodies and satellites in the Solar System with an unprecedented level of detail and that it achieves contrasts of the order 1e-4 with its H-alpha filter (1nm FWHM) at 150 mas separation from a mag G14 star, even under non-optimal weather conditions.

CaNaPy is an experimental Laser Guide Star Adaptive Optics facility designed to demonstrate pre-compensation of a sodium LGS uplink beam, and to investigate wavefront sensing on the pre-compensated LGS using a Pyramid wavefront sensor. CaNaPy was installed at the 1m ESA OGS telescope at the Observatorio del Teide, Tenerife, in autumn 2023. Here we report on the commissioning phase activities followed by the first on-sky results on LGS uplink pre-compensation. CaNaPy is developed at ESO in collaboration with ESA, Durham University, IAC, INAF, and Microgate, with scientific collaborators from ANU and the RICAM institute.

We present first on-sky performance results of KalAO, the natural guide star adaptive optics imager on the 1.2m Swiss telescope in La Silla, Chile. It is designed to reach at least 30% Strehl in order to detect stellar companions as close as the 150mas in visible-light, at diffraction limit. KalAO was built to search for binarity in planet hosting stars by following-up planet candidates primarily from the TESS satellite survey. The optical design is optimised for the 450 to 900nm wavelength range and is fitted with SDSS griz filters. Wavefront control works down to I-magnitude 10 stars in order to probe the same parameter space as radial velocity instruments such as HARPS and NIRPS. The system first closed the loop on sky in November 2023 and reached diffraction limit imaging in February 2024. It can carry out AO corrected observation of up to 500 targets in one night, with a Strehl ratio of ≈30%.

The MMT AO exoPlanet characterization System is an upgrade for the 6.5-m MMT observatory to the 20-year-old MMTAO adaptive secondary mirror (ASM) with new electronics, a new AO system with two pyramid wavefront sensors spanning the visible through infrared, and a suite of upgraded science cameras optimized for studying the atmospheres of extrasolar planets. We began on-sky engineering and commissioning in October 2022, and have progressed through first light to calibrations at this time. The AO system is complex with its dual wavefront sensors, and the ASM can only be calibrated on-sky. We will present the current status and results of commissioning the MAPS AO system.

The Adaptive Optics (AO) of the Gran Telescopio Canarias (GTC) is a single conjugate postfocal system, integrated in one of the Nasmyth platforms of the telescope. GTC is located in the Observatory of Roque de Los Muchachos (ORM) in the island of La Palma, Spain. GTCAO is based on a single deformable mirror (DM) with 373 actuators, conjugated to the GTC pupil, and a Shack-Hartmann wavefront sensor (WFS) with 312 useful sub-apertures on an OCAM2 camera. The performance required for GTCAO is 65% Strehl Ratio in K-band under average atmospheric conditions and bright NGS. After finishing its laboratory testing and calibration in 2022, the laboratory acceptance and transport readiness review took place in April 2023. GTCAO integration in the telescope was carried out along June 2023. The GTCAO control software was integrated with the GTC observing software along July, to implement the optical derotation, the WFS positioning in the field and guiding, the WFS atmospheric dispersion compensation, and the tip-tilt correction loop implemented with the GTC secondary mirror. At the end of Summer 2023 started the on-sky commissioning. Since then, the AO loop has been closed on sky in different turbulence and guide star conditions. This paper presents the GTCAO integration results and first on sky commissioning results.

The wide field adaptive optics system for solar observations had been developed and put in routine operation at the 1-meter New Vacuum Solar Telescope (NVST) in Fuxian Lake, Yunnan Observatory. This system adopts the configuration based on the high order ground layer correction loop and the low order high altitude correction loop. Three correction modes, namely the conventional adaptive optics (CAO), ground layer adaptive optics (GLAO), and multi-conjugate adaptive optics (MCAO) with three layers correction, can be chosen with the science requirement. The DM for ground layer correction is inherited from the 151-element AO system, and two new DMs are added and conjugated to 2~5km and 7~10km, respectively. The opto-mechanical design allows for changing the conjugate height of the two DMs independently. Two multi-direction Shack-Hartmann wavefront sensors are employed for sensing the aberration from ground layer and high-altitudes turbulence. The control system is based on multi-core CPUs platform, which is flexible for testing various control approaches. We summarize the design and report the observational results of different correction modes.

We installed the next-generation automated laser adaptive optics system, Robo-AO-2, on the University of Hawaii 2.2-m telescope on Maunakea in 2023. We engineered Robo-AO-2 to deliver robotic, diffraction-limited observations at visible and near-infrared wavelengths in unprecedented numbers. This new instrument takes advantage of upgraded components, manufacturing techniques and control; and includes a parallel reconfigurable natural guide star wavefront sensor with which to explore hybrid wavefront sensing techniques. We present the results of commissioning in 2023 and 2024.

We present progress on a conceptual design for a new Keck multi-conjugate adaptive optics system capable of visible light correction with a near-diffraction-limited spatial resolution. The KOLA (Keck Optical LGS AO) system will utilize a planned adaptive secondary mirror (ASM), 2 additional high-altitude deformable mirrors (DMs), and ≳8 laser guide stars (LGS) to sense and correct atmospheric turbulence. The field of regard for selecting guide stars will be 2’ and the corrected science field of view will be 60”. We describe science cases, system requirements, and performance simulations for the system performed with error budget spreadsheet tools and MAOS physical optics simulations. We will also present results from trade studies for the actuator count on the ASM. KOLA will feed a new optical imager and IFU spectrograph in addition to the planned Liger optical + infrared (λ>850nm) imager and IFU spectrograph. Performance simulations show KOLA will deliver a Strehl of 12% at g’, 21% at r’, 53% at Y, and 87% at K bands on axis with nearly uniform image quality over a 40”×40” field of view in the optical and over 60”×60” beyond 1 μm. Ultimately, the system will deliver spatial resolutions superior to HST and JWST (∼17 mas at r’-band) and comparable to the planned first-generation infrared AO systems for the ELTs.

MAVIS passed the Preliminary Design Review in March 2023 and kick started its phase C early June. We are aiming at a Final Design Review in December 2024. I will report on the state of MAVIS design, as well as general project updates, schedule, procurement, risks. We are working on early procurement (Long Lead Item review held on October 2023) as well as on a number of prototype activities I will report on.

The Gemini North Adaptive Optics (GNAO) facility is the upcoming Adaptive Optics (AO) facility for Gemini North providing a state-of-the-art AO system for surveys and time domain science in the era of James Webb Space Telescope (JWST) and Rubin operations. GNAO will be optimized to feed the Gemini Infrared Multi Object Spectrograph (GIRMOS). The GNAO project includes the development of a new laser guide star facility which will consist of four side launched laser beams supporting the two primary AO modes of GNAO: a wide-field mode providing an improved image quality over natural seeing for a 2-arcminute circular field-of-view using Ground Layer AO (GLAO) and a narrow-field mode providing near diffraction-limited performance over a 20 × 20 arcsecond square field-of-view using Laser Tomography AO (LTAO). After a competitive phase A study among three teams for the conceptual design of the AO bench, one team has been selected to complete the design, build and commissioning it at the telescope. We will be presenting the overall GNAO facility design, including specifics related to the AO bench and its architectural design. We will provide updates on all subsystems of the facility.

The first scientific observations with adaptive optics (AO) at W. M. Keck Observatory (WMKO) began in 1999. Through 2023, over 1200 refereed science papers have been published using data from the WMKO AO systems. The scientific competitiveness of AO at WMKO has been maintained through a continuous series of AO and instrument upgrades and additions. This tradition continues with AO being a centerpiece of WMKO’s scientific strategic plan for 2035. We will provide an overview of the current and planned AO projects from the context of this strategic plan. The current projects include implementation of new real-time controllers, the KAPA laser tomography system and the HAKA high-order deformable mirror system, the development of multiple advanced wavefront sensing and control techniques, the ORCAS space-based guide star project, and three new AO science instruments. We will also summarize steps toward the future strategic directions which are centered on ground-layer, visible and high-contrast AO.

The Large Binocular Telescope (LBT) Observatory pioneered Adaptive Optics (AO) technologies such as Adaptive Secondary Mirror (ASM), Pyramid wavefront sensor, and Ground-layer AO using Rayleigh lasers at 8 to 10m class telescopes. We have initiated an effort to turn LBT AO into a facility-class capability. The effort involves (1) building an AO team with AO development capability, (2) improving the robustness of the AO, (3) developing in-house AO expertise to maintain and troubleshoot the AO systems, (4) automating processes for efficient on-sky operation, (5) tracking performance metrics and cultivating accountability for on-sky AO performance, and (6) minimizing the operational risks for the ASMs. We present the status of these developments. LBTO continues its efforts to develop innovative technology. We explore the next phase of AO developments, including Agile Extreme Adaptive Optics (AgXAO) on the DX side of the LINC-NIRVANA optical bench to overcome the limitation imposed by varying and large atmospheric seeing at Mount Graham. AgXAO implementation includes the development of (1) a high-order, high-sensitivity wavefront sensor, (2) a high-density deformable mirror with 3000 actuators and next-generation ASM with about 950 actuators, (3) active optics integration, (4) vibration and wavefront piston control, (5) atmospheric turbulence measurements and weather forecast integration, and (6) a visible camera and an AO-corrected narrow-field fiber-coupled IFU spectrograph using one of the existing workhorse visible spectrographs. Developing AgXAO on the SX side, too, would enable Fizeau imaging in the visible wavelengths. AgXAO will also serve as a general-purpose high-contrast (and subsequently a Fizeau imaging) Testbed on LBT to test advanced wavefront control algorithms, including astrophotonics experiments, and machine learning algorithms with minimal impact on routine science operations. We propose developing AgXAO through student projects to train the next-generation scientists and engineers for the extremely large telescope (ELT) era. The ultimate goal is to push large aperture ground-based telescopes to their performance limits and make them competitive with space telescopes in terms of PSF stability and performance to enable breakthrough science.

Gemini Observatory operates twin 8m telescopes, one located in the Southern hemisphere, on Cerro Pachón in Chile, and one located in the Northern hemisphere, on Maunakea in Hawai’i. Currently, the Observatory operates 2 Adaptive Optics (AO) systems. Gemini South is equipped with the Gemini Multi-Conjugate Adaptive Optics System (GeMS), a wide field AO system, operating with 5 laser-guide stars and providing a uniform image quality (10% to 30% Strehl Ratio in the 1 to 2.5μm range) over an 85”x85” field-of-view. The ALTitude conjugate Adaptive optics for the InfraRed NGS/LGS Single-Conjugate Adaptive Optics system which operates in the 1 to 2.5μm range is located at Gemini North. A new AO workhorse facility is currently being developed for Gemini North, the Gemini North Adaptive Optics system (GNAO) which will feed the Gemini Infrared Multi-Object Spectrograph (GIRMOS). GNAO has a wide-field mode with improved image quality over a 2 arcminute field-of-view (FoV), and a laser tomography mode with diffraction-limited performance over a 20”x20” FoV. GIRMOS implements multi-object adaptive optics for each of its four integral field spectrographs; it also contains a near infrared imager, which can benefit from both wide and narrowfield AO capabilities. In addition, the Gemini Planetary Imager completed its science mission at Gemini South, is currently being upgraded (GPI2.0) and is planned to be installed at Gemini North in 2025. A wide-field Ground-Layer Adaptive Optics feasibility study using an Adaptive Secondary Mirror has been completed and preparations for a Conceptual Design Study are underway. This paper summarizes our operational adaptive optics (AO) facilities, the status of our ongoing AO development projects, and finally our longer-range observatory AO roadmap.

Optical Space Domain Awareness (SDA) aims to provide high-quality angular (and possibly spectral/polarimetric) information on LEO and GEO satellites for object characterization and identification. In terms of spatial resolution, the goal is to achieve decimetric resolution for low-Earth orbit and decametric resolution for geostationary orbit (in order to monitor the satellites' immediate environment). This ambitious objective can only be achieved by combining a large telescope, a dedicated AO system optimized for the specific characteristics of SDA, differential imaging capabilities and post-processing techniques ranging from Point Spread Function estimation to data fusion, including multi-frame deconvolution. We will present an overview of the key ingredients required to achieve an efficient and operational system and the status of ONERA's new project called PROVIDENCE. It is based on a 2.5m adaptive optics telescope optimized for SDA activities. It will be installed at Observatoire de Haute Provence (in south of France) and should see its first light at the end of 2028.

Chromatic effects can seriously limit Adaptive Optics performance when a telescope is used at large zenith angles, either because of the wavelength range being corrected or because the laser guide star (LGS) is at a different wavelength to the science observation. There are two types of Refractive effect - the first is due to the fact that the refractive index of air depends on wavelength, giving rise to different wavelengths having not having the same path length. The second, referred to here as chromatic anisoplanatism, is due to the fact that bending of light due to atmospheric refraction causes rays of different wavelengths to take different paths through the turbulence. In this article we consider chromatic anisoplanatism in more detail, and extend the analysis to consider a spherical rather than a planar atmosphere model. As a particular case we investigate the effect for the ESO Extremely Large Telescope, employing a layered model for the turbulence above the ELT site at Cerro Armazones.

The lifetime of current AO systems can span decades, from the first ideas to decommissioning. During this time, computer systems, from operating systems to programming languages to data analysis methods can change fundamentally. This can be a challenge for AO simulations, where very old results sometimes need to be "resurrected", re-analyzed, reproduced or changed. In this contribution, I will present a range of methods that have been used to shield simulation tools from unwanted changes, and how we manage to still exactly the same results as 15 years ago, if needed. We can still run exactly the same simulations as when they were first done, if needed, and can update only the desired parameters in a controlled fashion. I will also present a range of things that can go wrong if a simulation environment is left to drift uncontrollably.

In the design process of large adaptive mirrors numerical simulations represent the first step to evaluate the system design compliance in terms of performance, stability and robustness. To this end an efficient and accurate digital twin is required, which represents the deformable mirror and consists of complex physical models. For the next generation of Extremely Large Telescopes increased system dimensions and increased bandwidths lead to the need of modeling not only the deformable mirror alone, but also all the system supporting structure or even the full telescope. We present our high fidelity digital twin, which allows to perform the simulations within an acceptable amount of time and computational resources. The control strategy of the adaptive mirror is based on a mix between feedforward (FF) and feedback (FB) contributions. In this context optimized control parameters are important to improve both the system disturbance rejection and tracking performance. We analyze the feasibility of our digital twin via high fidelity simulations for the P72 prototype of the adaptive mirror of the Giant Magellan Telescope.

Great progress has been made applying deep learning methods to adaptive optics (AO) control, focus has largely been on reinforcement learning (RL) methods. While RL is a powerful tool and shows promising results, it requires continual learning while on sky to truly be effective. This makes it difficult to apply optimization techniques, such as kernel compilation, pruning, or – in the most extreme cases – hard coded networks in hardware, which may be necessary for high speed extreme AO control. We present a method and optical bench results for supervised training of AO predictive control networks trained using only simulated data. This can be accomplished by varying both the optical parameters of the AO system as well as the parameters of the simulated atmosphere; teaching the network to generalize for optical as well as atmospheric conditions. Our method also alleviates issues with both online and supervised learning methods trained on saved telemetry which may over-fit to local conditions that can vary from night to night. This training methodology is general enough to be widely applicable among most AO systems and has proven to be effective in our optical bench experiments.

The rise of extreme Large Telescopes (ELTs) poses challenges for high-resolution phase map reconstruction. Despite the pyramid wavefront sensor (PyWFS) promise, its inherent non-linearity is limiting. This study proposes techniques to enhance the non-modulated PyWFS linearity through deep learning, comparing convolutional Neural Networks (CNNs) models (Xception, WFNet, ConvNext) with the transformer model Global Context Vision Transformers (GCViT). Results favor transformers, highlighting CNN limitations near pupil borders. Experimental validation on the PULPOS optical bench underscores the GCViT robustness. Trained solely on simulated data under varied SNR and D/r₀ conditions, our approach enables to accurately close the AO loop in a real system and leave behind the reconstruction paradigm based on the interaction matrix. We demonstrate the high performance of the GCViT in closed loop obtaining a Strehl ratio over 0.6 for strong turbulence and nearly 0.95 for weak turbulence on the PULPOS optical bench.

Performances of an adaptive optics (AO) system are directly linked with the quality of its alignment. During the instrument calibration, having open loop fast tools with a large capture range are necessary to quickly assess the system misalignment and to drive it towards a state allowing to close the AO loop. During operation, complex systems are prone to misalignments (mechanical flexions, rotation of optical elements, etc.) that potentially degrade the AO performances, creating a need for a monitoring tool to tackle their driftage. In this work, we first present an improved perturbative method to quickly assess large lateral errors in open loop. It uses the spatial correlation of the measured interaction matrix of a limited number of 2D spatial modes with a synthetic model. Then, we introduce a novel solution to finely measure and correct these lateral errors via the closed loop telemetry. Non-perturbative, this method consequently does not impact the science output of the instrument. It is based on the temporal correlation of 2D spatial frequencies in the deformable mirror commands. It is model-free (no need of an interaction matrix model) and sparse in the Fourier space, making it fast and easily scalable to complex systems such as future extremely large telescopes. Finally, we present some results obtained on the development bench of the GRAVITY+ extreme AO system (Cartesian grid, 1432 actuators). In addition, we show with on-sky results gathered with CHARA and GRAVITY/CIAO that the method is adaptable to non-conventional AO geometries (hexagonal grids, 60 actuators).

The next generation of extreme adaptive optics (AO) must be calibrated exceptionally well to achieve the desired contrast for ground-based direct imaging exoplanet targets. Current wavefront sensing and control system responses deviate from lab calibration throughout the night due to non linearities in the wavefront sensor (WFS) and signal loss. One cause of these changes is the optical gain (OG) effect, which shows that the difference between actual and reconstructed wavefronts is sensitive to residual wavefront errors from partially corrected turbulence. This work details on-sky measurement of optical gain on MagAO-X, an extreme AO system on the Magellan Clay 6.5m. We ultimately plan on using a method of high-temporal frequency probes on our deformable mirror to track optical gain on the Pyramid WFS. The high-temporal frequency probes, used to create PSF copies at 10-22 λ/D, are already routinely used by our system for coronagraph centering and post-observation calibration. This method is supported by the OG measurements from the modal response, measured simultaneously by sequenced pokes of each mode. When tracked with DIMM measurements, optical gain calibrations show a clear dependence on Strehl Ratio, and this relationship is discussed. This more accurate method of calibration is a crucial next step in enabling higher fidelity correction and post processing techniques for direct imaging ground based systems.

With the commissioning of the refurbished adaptive secondary mirror (ASM) for the 6.5-meter MMT Observatory under way, special consideration had to be made to properly calibrate the mirror response functions to generate an interaction matrix (IM). The commissioning of the ASM is part of the MMT Adaptive optics exo- Planet characterization System (MAPS) upgrade the observatory’s legacy adaptive optics (AO) system. Unlike most AO systems, MAPS employs a convex ASM which prevents the introduction of a calibration source capable of simultaneously illuminating its ASM and wavefront sensor (WFS). This makes calibration of the AO system a significant hurdle in commissioning. To address this, we have employed a hybrid calibration strategy we call the Efficient Synthesis of Calibrations for Adaptive Optics through Pseudo-synthetic and Empirical methods (ESCAPE). ESCAPE combines the DO-CRIME on-sky calibration method with the SPRINT method for computing pseudo-synthetic calibration matrices. To monitor quasi-static system change, the ESCAPE methodology rapidly and continuously generates pseudo-synthetic calibration matrices using continual empirical feedback in either open or closed-loop. In addition, by measuring the current IM in the background while in close-loop, we are also able to measure the optical gains for pyramid wavefront sensor (PyWFS) systems. In this paper, we will provide the mathematical foundation of the ESCAPE calibration strategy and on-sky results from its application in calibrating the MMT Observatory’s ASM. Additionally, we will showcase the validation of our approach from our AO testbed and share preliminary on-sky results from MMT.

Fourier Filtering WaveFront Sensors (FFWFS) are extremely sensitive wavefront sensors that will improve the wavefront estimation of large ground-based facilities such as European Extremely Large Telescope (ELT) or Giant Magellan Telescope (GMT). Yet they suffer from inherent non-linear behaviour that prevents their optimised use. We propose a modification of the calibration process of these sensors to implement their non linearities in the matrix formalism (linear formalism). The new approach called the specific matrix tackles the loss of sensitivity and the modal confusion of the FFWFS. It allows the measurement of the absolute phase and to close the loop using a non-modulated pyramid. We demonstrate this method by use of numerical simulations.

High-contrast imaging instruments face performance limitations due to non-common path aberrations, which hinder the detection of exoplanets. We have successfully applied convolutional neural networks to estimate these aberrations using simulations. However, training a model on simulated data before inferring the phase aberrations on real data leads to inaccuracies. In this study, we propose a domain adaptation method, based on a variational autoencoder architecture, to swiftly adapt models from simulations to real data. We employ the Subaru/SCExAO instrument and showcase how our approach significantly enhances phase retrieval.

The rise of exoplanet research and the growing need for high-capacity free-space optical communication links have placed high demands on the performance of adaptive optics (AO) systems. A key challenge lies in mitigating temporal error, this imposes severe time constraints on the response of deformable mirrors (DM). Recent advancements at ALPAO in the realm of input shaping techniques have yielded promising results, effectively eliminating oscillations and reducing overshoot from 60 to less than 5%. Both, rise time and settling time have been diminished to below 50μs, representing an improvement of one order of magnitude compared to the unshaped case. The solution found is compatible with real-time computing constraints and can be integrated in the DM drive electronics or in separate processing unit.

Recent work by Oberti+22 argued and showed that classical astronomical adaptive-optics tomography performance can be further improved by carefully designing and configuring the system to encompass and exploit any built-in super-resolution (SR) capabilities. Our goal now is to further materialise the concept by outlining the key models to compute SR-enabling tomographic reconstructors for AO. For that we assume the form of a review paper where we (i) clarify how model-and-deploy static reconstructors arise naturally from the solution of the inverse problem and how to make them cope with closed-loop systems, (ii) how this solution is obtained as a limiting-case of a properly-conceived optimal stochastic control problem, (iii) review the two forms of the minimum-mean-squared-error (MMSE) tomographic reconstructors, highlighting the necessary adaptations to accommodate super-resolution, (iii) review the implementation in either dense-format vector-matrix-multiplication or sparse iterative forms and (iv) discuss the implications for runtime and off-line real-time implementations. We illustrate our examples with simulations/on-sky results when possible for 10m and 40m-scale systems.

Predictive control laws for Adaptive Optics (AO) using Artificial Intelligence has been recently explored as an alternative to the classic methods, such as the integrator law. Reinforcement Learning excels in predictive control tasks by enabling systems to learn optimal control strategies through continuous interaction with their environment, adapting to dynamic conditions and achieving effective decision-making in real-time. In our previous work, a Model-based Reinforcement Learning (MBRL) method called Policy Optimization for Adaptive Optics (PO4AO) was used in conjunction with the Object-Oriented Python Adaptive Optics (OOPAO) to simulate the Provence Adaptive Optics Pyramid Run System (PAPYRUS) optical bench. PO4AO demonstrated high adaptability to turbulence and rapid convergence, achieving optimal corrections after just 500 frames of interaction, outperforming a simulated integrator in different atmospheric conditions. Building upon this, our current study explored PO4AO’s capability to adapt to sudden atmospheric changes by worsening turbulence conditions during evaluation, notably the wind speed and the seeing. In the result’s section, we compare PO4AO’s performance in terms of Strehl Ratio (SR) to the integrator. Further description of the experiments are present in the paper.

In order to address new science objectives in exoplanet imaging, the SAXO+ technical development project has been undertaken for the SPHERE instrument at ESO’s VLT. As a part of this, the AO system will be completed by adding a second, faster stage of correction. We present simulation results obtained by implementing an optimal predictive linear quadratic Gaussian controller for the 2nd stage. The prediction relies on a stochastic state-space disturbance model fully identified from closed-loop measurements. In addition, we also investigate a disentangled cascade AO (dCAO) mode whIn order to address new science objectives in exoplanet imaging, the SAXO+ technical development project has been undertaken for the SPHERE instrument at ESO’s VLT. As a part of this, the AO system will be completed by adding a second, faster stage of correction. We present simulation results obtained by implementing an optimal predictive linear quadratic Gaussian controller for the 2nd stage. The prediction relies on a stochastic state-space disturbance model fully identified from closed-loop measurements. In addition, we also investigate a disentangled cascade AO (dCAO) mode where the model represents the full incoming disturbance and is identified using in addition the 1st stage commands.ere the model represents the full incoming disturbance and is identified using in addition the 1st stage commands.

Almost all current and future high-contrast imaging instruments will use a Pyramid wavefront sensor (PWFS) as primary or secondary wavefront sensor. The main issue with the PWFS is its nonlinear response to large phase aberrations, especially under strong atmospheric turbulence. In this talk, we will present closed-loop lab results of a nonlinear reconstructor for the unmodulated PWFS of MagAO-X based on Convolutional Neural Networks. We show that our nonlinear reconstructor has a dynamic range of >600 nm rms, significantly outperforming the linear reconstructor that only has a 50 nm rms dynamic range. The reconstructor behaves well in closed-loop and can obtain >80% Strehl under a large variety of conditions and reaches higher Strehl ratios than the linear reconstructor under all simulated conditions. The CNN reconstructor implementation also achieves the theoretical sensitivity limit of a pyramid wavefront sensor showing that it does not lose its sensitivity in exchange for dynamic range. The current CNN’s computational time is 690 us which enables systems to run at >1 kHz. We will also discuss the real-time implementation on MagAO-X and show preliminary on-sky tests.

In this communication, we report on the results of the second phase of the Exoplanet Imaging Data Challenge started in 2019. This second phase focuses on the characterization of point sources (exoplanet signals) within multispectral high-contrast images from ground-based telescopes. We collected eight data sets from two high-contrast integral field spectrographs (namely Gemini-S/GPI and VLT/SPHERE-IFS) that we calibrated homogeneously and in which we injected a handful of synthetic planetary signals (ground truth) to be characterized by the data challenge participants. The tasks of the participants consist of (1) extracting the precise astrometry of each injected planetary signals, and (2) extracting the precise spectro-photometry of each injected planetary signal. Additionally, the participants may provide the 1-sigma uncertainties on their estimation for further analyses. When available, the participants can also provide the posterior distribution used to estimate the position/spectrum and uncertainties. The data are permanently available on a Zenodo repository and the participants can submit their results through the EvalAI platform. The EvalAI submission platform opened on April 2022 and closed on the 31st of May 2024. In total, we received 4 valid submissions for the astrometry estimation and 4 valid submissions for the spectrophotometry (each submission, corresponding to one pipeline, has been submitted by a unique participant). In this communication, we present an analysis and interpretation of the results.

The high contrast and spatial resolution requirements for directly imaging exoplanets requires effective coordination of wavefront control, coronagraphy, observation techniques, and post-processing algorithms. However, even with this suite of tools, identifying and retrieving exoplanet signals embedded in resolved scattered light regions can be extremely challenging due to the increased noise from scattered light off the circumstellar disk and the potential misinterpretation of the true nature of the detected signal. This issue pertains not only to imaging terrestrial planets in habitable zones within zodiacal and exozodiacal emission but also to young planets embedded in circumstellar, transitional, and debris disks. This is particularly true for Hα detection of exoplanets in transitional disks. This work delves into recent Hα observations of three transitional disks systems with MagAO-X, an extreme adaptive optics system for the 6.5-meter Magellan Clay telescope. We employed angular differential imaging (ADI) and simultaneous spectral differential imaging (SSDI) in combination with KLIP, a PCA algorithm in post-processing, for optimal starlight suppression and quasi-static noise removal. We discuss the challenges in protoplanet identification with MagAO-X in environments rich with scattered and reflected light from disk structures and explore a potential solution for removing noise contributions from real astronomical objects with current observation and post-processing techniques.

The Enhanced Resolution Imager and Spectrograph (ERIS) is the new near-infrared instrument at the VLT-UT4. ERIS replaces and extends the observational capabilities formerly provided by SINFONI and NACO: integral field spectroscopy at 1 to 2.5μm, imaging at 1 to 5μm with several options for high-contrast imaging, and long-slit spectroscopy. In particular, a vortex coronagraph is now available for high contrast observations at L and M band. It is implemented using annular groove (or vortex) phase masks (one for each of the L and M bands) in a focal plane, and a Lyot stop in a downstream pupil plane. The vortex coronagraph has a discovery space starting already at ∼1λ/D, and works well in broadbands. However, to reach its optimal performance, it is critical to correct for slow pointing errors onto the vortex phase mask, which mandates a dedicated pointing control strategy. To do so, a control loop based on the QACITS algorithm has been developed and commissioned for ERIS. Good pointing stability is now regularly achieved with errors between 0.01 and 0.02 λ/D and a correction rate of 0.2Hz. In this contribution, we first review the design of the ERIS vortex coronagraph. We then detail the implementation of the QACITS algorithm describing the entire observing sequence, including the calibration steps, the initial centering, and the stabilization during the observing template. We then discuss performance based on commissioning data in terms of pointing accuracy and stability. Finally, we present post-processed contrast curves obtained during commissioning and compare them with NACO vortex data, showing a significant improvement of about 1 mag at all separations.

PAPYRUS is an adaptive optics bench setup on the telescope T152, 1.52m diameter, of Observatoire de Haute Provence (OHP, France) since June 2022. This bench has been designed for research and development in adaptive optics and educational purposes. However it gained in maturity since its first light and is now evolving towards an instrumental platform, including infrared capacities (imager, fiber injection module). So equipped, the bench will mature concepts and techniques coupling adaptive optics and their associated instruments, for future systems such as the 2.5m PROVIDENCE system that will also be located at OHP or for the HARMONI instrument to be installed at ELT. PAPYRUS features a four-sided pyramid in front of an EMCCD camera working in broadband visible and a deformable mirror made of 241 actuators. We review here the current status of the bench, its performances and its on-going developments.

Japanese astronomical adaptive optics development began in the 1990s for the system to be installed on the 8.2-m Subaru Telescope of the National Astronomical Observatory of Japan. Currently, development is underway, including 188-element laser guide star AO, SCExAO for exoplanet observations, and GLAO using an adaptive secondary mirror in collaboration with Tohoku University for the telescope. Kyoto University is now developing AO for its 3.8-m Seimei telescope. Kyoto Sangyo University, Okayama University of Science, and other universities have established development groups. In addition, research on AO for microscopy and space optical communications is being conducted in collaboration with astronomical groups.

Solar prominences are dim protruding features outside the solar limb that are not routinely observed using adaptive optics yet. Conventional wavefront sensors at solar telescopes cannot use them as a target because they are designed to operate on very bright, weak contrast photospheric features. It was first demonstrated in 2013 at NSO's 0.7-meter Dunn Solar Telescope that it is possible to use prominences as a wavefront sensing reference in a correlating Shack-Hartmann sensor optimized for this purpose. The development of a wavefront sensor for prominences has since been continued at the 1.6-meter Goode Solar Telescope in collaboration with NJIT's Big Bear Solar Observatory. With the latest revision of a wavefront sensor prototype in the summer of 2023, we were able to observe prominences in H-alpha as well as other features such as coronal rain and emerging loops with high-order adaptive optics correction. We will present stunning movies of highly dynamic and small scale events outside the solar limb, present the design of the wavefront sensor and estimate the performance of the adaptive optics correction.

Combining extreme-AO correction with single-mode fiber (SMF) spectroscopy is a promising approach for Extreme Precision Radial Velocity, possibly reaching the cm/s level required for identification of Earth analogs. SMF spectrographs however exhibit a RV bias error due to coupling between stellar rotation and spatially-variant coupling efficiency, with amplitudes reaching ~m/s level on large telescopes. We explore using a spectrally dispersed photonic lantern (PL) for simultaneous RV and WFS measurements, and calibrate the RV bias error using WFS telemetry. On-sky observations of the star Humu (Altair) at the Subaru Telescope with SCExAO have confirmed the RV bias effect at the expected 5 km/s amplitude. Using a 19-port PL and a R=4000 spectrograph, we have demonstrated PL-based calibration of the RV-bias to <200 m/s, approaching the photon noise limit. The ExAO+PL+spectrograph is a precursor to a RV instrument at higher spectral resolution.

The development of Adaptive Optics (AO) has made ground based telescopes increasingly competitive with those in space. However, AO cannot correct for atmospheric scintillation noise, which severely limits the precision of time resolved photometry for ground-based observations of bright stars, such as exoplanet transits. A scintillation correction technique has been proposed and tested on-sky that uses tomographic wavefront sensing and turbulence profile measurements to produce an estimate of the intensity fluctuation due to scintillation that can be used to correct the photometric data. We will present a demonstration of this scintillation correction technique using data from the Adaptive Optics Facility (AOF) at the Very Large Telescope (VLT). Simulations of this facility suggest reductions of up to a factor of four in the scintillation noise RMS could be achieved. This could enable far greater precision in exoplanet transit analysis, and hence detections of much smaller planets, from the ground.

Laser guide stars (LGSs) are used as an artificial star to detect wavefront aberrations in adaptive optics (AO) systems, however the tip tilt (TT) motion is not visible due to the reciprocal propagation of the light. This significantly limits the sky coverage of AO systems, requiring the presence of a natural guide star (NGS) for TT correction. We describe a novel approach for detecting TT from a LGS, by observing the LGS produced by an amplitude modulated laser from multiple (>3) auxiliary telescopes, and measuring the relative time taken for the wavefront to arrive at each telescope. This can be used to calculate TT motion without the necessity of a NGS. By implementing this technique, AO systems could achieve full sky coverage, significantly enhancing their utility in astronomical observations and potential in free space optical communications. We describe the technique and discuss the advantages and many challenges with this system.

As of today, Laser Guide Star adaptive optics can not measure the image motion induced by atmospheric turbulence. In this paper we review one of the proposed methods, never tested: the time-delay method. We will look at its application for the 1m class CaNaPy system, for the 8m class systems and potentially for extremely large telescopes. ESO and ESA are collaborating in this R&D, creating the CaNaPy-LASCA LGS-AO facility for both, Astrophysics and Optical Communications field experiments. We present the concept, its optimal setup, the potential difficulties of the time-delay method as well as the numerical simulations results when retrieving the atmospheric tip-tilt, for different telescope diameters, including the 8m+ class telescopes.

Current pupil-plane adaptive optics (AO) systems face two challenges: non-common-path aberrations (NCPAs), caused by path differences between the sensing and science arms of an instrument; and petaling, discontinuous aberrations which arise for systems with large, fragmented pupils. One solution is to add a dedicated wavefront sensor (WFS) which senses aberrations in the final focal plane. Previous work has demonstrated real-time wavefront control from the final focal plane using the intensity pattern of a photonic lantern (PL): a waveguide that can couple an aberrated telescope beam into multiple single-mode fibers. Here, we consider the next logical extension, where PL outputs are additionally spectrally dispersed. The additional phase information provided by spectral dispersion can potentially expand both the number of corrected modes and the dynamic range of the PL WFS. Simultaneously, a dispersed PL can enable powerful techniques such as high-resolution spectroscopy and spectroastrometry. To this end, we present an analysis of the dispersed PLWFS, in the process developing implementation strategies and culminating in an experimental demonstration on the SCExAO testbed.

This paper provides an overview of the various ways in which the Gender Equity in Astronomy invited presentation at the 2014 SPIE Adaptive Optics conference has contributed to shift the discourse around gender equity and gender equality in our field over the past 10 years. In Part I of this paper, the preliminary results of the 2024 survey of the international adaptive optics community are presented to quantify how the representation of women in adaptive optics has evolved since the initial survey was conducted in 2014. The 2024 survey also investigates how diverse the international AO community is across other diversity characteristics such as sexual orientation, disability, language, and geography. In Part II, small, medium and large-scale practical initiatives to achieve greater inclusion, diversity, equity and access in adaptive optics and astronomy are showcased to demonstrate how bold leadership and ambitious objectives and strategies can lead to effective and positive change in that space.

In the recent Astro2020 Decadal Report, “Pathways to Discovery in Astronomy and Astrophysics for the 2020s” Adaptive Optics (AO) was identified as a crucial technology for a variety of reasons. These included an emphasis on high-contrast imaging and AO systems as being part of future technology development especially with application to the two US ELT projects. Instrument upgrades were also identified for existing 4-10m class telescopes which would incorporate upgrades to existing AO systems. A workshop was held in May, 2023 to develop a Community Response document to provide feedback and suggested priorities to various funding agencies, such as NSF, NASA, and DoE, as to the AO R&D priorities to meet the technical and science objectives outlined in Astro2020 for ground-based AO, both stand-alone and in support of space missions. We report on the outcome of this workshop outlining the recommendations included in the Adaptive Optics Community Report for future AO systems to support the Astro2020 Science Goals.

The Cassiopée project aims to develop the key technologies that will be used to deploy very high-performance Adaptive Optics for future ELTs. The ultimate challenge is to detect earth-like planets and characterize the composition of their atmosphere. For this, imaging contrasts of the order of 10^9 are required, implying a leap forward in adaptive optics performance, with high density deformable mirrors (>100x100 actuators), low-noise cameras and the control of the loop at few kHz. The project brings together 2 industrial partners: First Light Imaging and ALPAO, and 2 academic partners: ONERA and LAM, who will work together to develop a new camera for WFSensing, a new deformable mirror and their implementation in an AO loop.

The use of a photonic lantern as focal plane wavefront sensor has seen recent widespread interest – it can remove non-common-path aberrations, accurately sense low-wind-effect and petal modes, and provide wavelength resolution. It encodes both the PSFs phase and amplitude into the intensities of its single-mode-fibre outputs, from which the wavefront is reconstructed (by neural network or other algorithm). It also offers exciting potential as an imager to resolve structure at and beyond the telescope diffraction limit, filling in a coronagraphs IWA blind spot. This can utilise interferometric techniques, or an oversampled photonic lantern, having sufficient measurement dimensions that the amplitude, phase and spatial coherence of the science field can be entirely constrained by the output fluxes, and so the wavefront-error-induced components can be disambiguated from the source spatial structure. Other applications such as fibre nulling, optimal single-mode fibre injection, spectroastrometry, and others are also in development. Here, a brief overview of the photonic lantern sensor and these various applications will be given, along with key references.

Exoplanet direct imaging using adaptive optics (AO) is often limited by non-common path aberrations (NCPAs) and aberrations that are invisible to traditional pupil-plane wavefront sensors (WFSs). This can be remedied by focal-plane (FP) WFSs that characterize aberrations directly from a final science image. Photonic lanterns (PLs) can act as low-order FPWFSs with the ability to direct some light to downstream science instruments. Using a PL on the SEAL (Santa Cruz Extreme AO Laboratory) high-contrast imaging testbed, we demonstrate (1) linear ranges and (2) closed-loop control. Additionally, we simulate the use of the PL in a multi-wavefront sensor AO system, in which multiple WFSs feed back to the same common-path deformable mirror. Building on previous multi-WFS AO demonstrations on SEAL, we simulate a modulated pyramid WFS to sense aberrations of high spatial order and large amplitude, and the PL to sense low order aberrations including NCPAs. We assess adaptive optics performance in this setting using three different PL wavefront reconstruction algorithms. We also provide a new method to experimentally identify the propagation matrix of a PL, making advanced model-based algorithms practical. This work demonstrates the role of photonic technologies and multi-stage wavefront sensing in the context of extreme AO and high contrast imaging.

All high-contrast imaging instruments are plagued by non-common path aberrations (NCPA). MagAO-X has a unique second-stage Adaptive Optics (AO) system that contains a dedicated deformable mirror (DM) that is not seen by the main AO wavefront sensor for NCPA compensation. Our second stage AO system decouples the focal plane wavefront control from the main AO loop that is driven by a pyramid wavefront sensor. This Non-Common Path Aberration Correction DM (ncpcDM) has been recently upgraded from an ALPAO-97 to a Boston Micromachine Kilo-DM. The large increase in the number of actuators on the ncpcDM enables high-order focal plane wavefront control algorithms such as implicit Electric Field Conjugation (iEFC). We developed iEFC on MagAO-X to create a data-driven approach to coronagraphic dark hole digging. Our preliminary results indicate that iEFC together with the second-stage AO system can improve the raw contrast of MagAO-X by one to two orders of magnitude with an even larger gain expected after post-processing. We will review the focal-plane wavefront sensing and control strategies of MagAO-X and present the first on-sky results of iEFC with the second-stage AO system.

The adaptive optics community is turning its attention to super-resolution-enabling designs (SR). These allow wavefront reconstruction at a higher-resolution from multiple lower-resolution samples. Such are the cases of tomographic sytems using multiple laser guide star Shack-Hartmann (SH) measurements.The extension of this concept to the pyramid wavefront sensors (PyWFS) has already been advocated, but the concept is not as straightforward as initially thought. Our goal is to provide a general proof of how SR can be exploited with PyWFSs, where we can draw from the analogy with SH-WFSs and where it they fundamentally different. Furthermore we show how phase and amplitude aberrations can be measured concomitantly and the new applications this opens. We provide analytic (diffraction theory), numerical (Monte Carlo physical optics simulations) and tentatively experimental (on-sky @ REVOLT) demonstrations. We illustrate results with several achievable performance metrics (Strehl-ratio, WFE, etc), aliasing rejection and noise propagation as well as design guidelines for how to increase SR capabilities across different PyWFS configurations.

The pyramid wavefront sensor has become an essential asset for extreme adaptive optics systems, as it offers a high sensitivity. Its main drawback remains its nonlinear behaviour. Using a gain sensing camera and a convolutional model enables the tracking of the first order nonlinearities, called the optical gains. They can be used in the reconstructor as an optimal modal gain integrator as they express the loss of sensitivity of the system in presence of residuals. Knowing them also makes it possible to offset the pyramid and maintain this offset during a closed loop. This operation allows to compensate for non-common path aberration, to maintain an absolute tip-tilt for fiber injection and to introduce dark-hole maps for high contrast imaging. This study explore the behaviour of the offsetted pyramid wavefront sensor assisted by a gain sensing camera, in simulation and experimentally with the AO-bench PAPYRUS.

The Zernike wavefront sensor (ZWFS) stands out as one of the most sensitive optical systems for measuring the phase of an incoming wavefront, reaching photon efficiencies close to the fundamental limit. This quality, combined with the fact that it can easily measure phase discontinuities, has led to its widespread adoption in various wavefront control applications, both on the ground but also for future space-based instruments. Despite its advantages, the ZWFS faces a significant challenge due to its extremely limited dynamic range, making it particularly challenging for ground-based operations. To address this limitation, one approach is to use the ZWFS after a general adaptive optics (AO) system; however, even in this scenario, the dynamic range remains a concern. This paper investigates two optical configurations of the ZWFS: the conventional setup and its phase-shifted counterpart, which generates two distinct images of the telescope pupil. We assess the performance of various reconstruction techniques for both configurations, spanning from traditional linear reconstructors to gradient-descent-based methods. The evaluation encompasses simulations and experimental tests conducted on the Santa cruz Extreme Adaptive optics Lab (SEAL) bench at UCSC. Our findings demonstrate that certain innovative reconstruction techniques introduced in this study significantly enhance the dynamic range of the ZWFS, particularly when utilizing the phase-shifted version.

The simultaneous push to unprecedented contrast, spectral and spatial resolution at the Very Large Telescope Interferometer (VLTI), as promised by the Asgard instrument suite, requires unprecedented high Strehl ratios and phase-front stability. This will be the job of Baldr: a new J or H band Zernike wavefront sensor (ZWFS) used as a second stage adaptive optics (AO) system for the VLTI/Asgard instrument suite. ZWFS was selected for Baldr due to its optimal photon sensitivity and the need for Baldr to be extremely low latency to reduce the residuals from the first stage AO systems. Here we briefly present the design of Baldr which uses a novel architecture where all four Baldr beams for adaptive optics from each telescope are sensed with a low-latency C-RED One detector, permitting AO frame rates up to 3.5kHz. With this architecture simulations show that the Baldr design can deliver J-band Strehl ratios for the 1.8m Auxiliary Telescopes (AT’s) of over 80%, which is a significant improvement on the Strehl ratios otherwise delivered to Asgard, which would limit the scientific objectives of the instrument. Finally we present preliminary test-bed results and give an overview of progress and future work.

We extend our previous demonstration of the first on-sky primary mirror segment closed-loop control on Keck using a vector-Zernike wavefront sensor (vZWFS), which improved the Strehl ratio on the NIRC2 science camera by up to 10 percentage points. Segment co-phasing errors contribute to Keck contrast limits and will be necessary to correct for the segmented Extremely Large Telescopes and future space missions. The goal of the post-AO vZWFS on Keck is to monitor and correct segment co-phasing errors in parallel with science observations. The ZWFS is ideal for measuring phase discontinuities and is one of the most sensitive WFSs, but has limited dynamic range. The Keck vZWFS consists of a metasurface mask imposing two different phase shifts to orthogonal polarizations, split into two pupil images, extending its dynamic range. We report on the vZWFS closed-loop co-phasing performance and early work towards understanding the interactions between the AO system and segment phasing. We discuss a comparison of the AO performance when co-phasing by aligning segment edges, as is currently done at Keck, compared with aligning to the average phase over the segments, as is done by the vZWFS.

Detecting dim exoplanets close to bright stars requires highly sensitive wavefront sensors that utilize the full spatial coherence of the pupil. This allows better measurement and correction of low-order modes, which diffract starlight close to the star. We present a closed-loop demonstration with three different wavefront sensors: the Shack Hartmann (SHWFS), the three-sided Pyramid (3PWFS), and the non-linear curvature Wavefront Sensor (nlCWFS), using a new wavefront sensor testbed. All three wavefront sensors simultaneously have light on them, however they are sequentially used to close the loop, using the single deformable mirror. We want to compare the performance of the three wavefront sensors for different traget brightness and atmospheric conditions.

The next generation of extremely large telescopes (ELTs) will require sensitive low order wavefront sensor (WFS), such as the pyramid wavefront sensor (PWFS), for first stage adaptive optics (AO) correction. Traditional PWFS utilize glass prisms to produce four pupils for wavefront measurement. Alternative optical designs have been realized to achromatize these sensors and increase their effective spectral range. Current WFSs optical designs are optimized for a specific bandpass, such as the visible and near-infrared. This may require deploying more than one WFS that is optically designed for its respective wavelength regime. To mitigate this challenge with transmissive WFSs, a three-sided reflective pyramid wavefront sensor (3-RPWFS) has recently been demonstrated on-sky using Shane Telescope at Lick Observatory. Because of its reflective design and wavelength independence, this WFS can operate at much larger spectral range, encompassing both the visible and near-infrared. In this paper, we present a new compact 3-RPWFS design optimizes space and characterize closed-loop adaptive optics performance.

The Gemini Planet Imager (GPI) is a high-contrast imaging instrument designed to directly detect and characterise young, Jupiter-mass exoplanets. After six years of operation at the Gemini South Telescope in Chile, the instrument is being upgraded and moved to the Gemini North Telescope in Hawaii as GPI 2.0. Several improvements have been made to the adaptive optics (AO) system as part of this upgrade. This includes replacing the current Shack-Hartmann wavefront sensor with a pyramid wavefront sensor (PWFS) and a custom EMCCD. These changes will increase GPI’s sky coverage by accessing fainter targets, improving corrections on fainter stars and allowing faster and ultra-low latency operations on brighter targets. The PWFS subsystem was independently built and tested to verify its performance before being integrated into the GPI 2.0 instrument. This paper will present the pre-integration performance test results, including pupil image quality, throughput and linearity without modulation.

We report on results from the laboratory wide-field phasing testbed that has been constructed to validate the active optics and piston sensing hardware and algorithms to be used on the Giant Magellan Telescope. The GMT is comprised of seven primary (M1) mirror segments, and seven secondary (M2) segments. To maintain a high quality wavefront across the full LTAO field-of-view, telescope aberrations must be controlled at M1 and M2 independently. This will be done on GMT using the 4 off-axis wavefront sensors of the Acquisition, Guiding and Wavefront-sensing System (AGWS). With the double segmented nature of the GMT, the most challenging aberration to control is field-dependent piston, which results from tilts of M1 segments that are compensated by tilts of the corresponding M2 segment. We report here on wavefront sensing experiments conducted with a full-scale prototype AGWS wavefront sensor fed by a GMT optical simulator called the Wide-Field Phasing Testbed (WFPT). With the WFPT we introduce aberrations on M1 and M2, including simulated atmospheric turbulence and a variety of guide-star magnitudes. The AGWS measures the resulting off-axis aberrations, and then corrects the M1 and M2 aberrations. We describe the wavefront reconstructors used to generate the corrections and the performance over a range of conditions.

The next generation of adaptive optics (AO) systems have chosen the pyramid wavefront sensor (PWFS) that is renowned for its performance in closed-loop AO. With the advent of the extremely large telescope era, it is essential to investigate methods to enhance PWFS performance further. Microwave Kinetic Inductance Detectors (MKID) are photon-counting devices that record the arrival time and energy of each incident photon. They offer new capabilities beyond those of existing detectors and can significantly improve AO performance. This project aims to demonstrate how the use of an MKID can improve PWFS performance to meet the demanding requirements of an ELT instrument through simulation, laboratory tests and finally an on-sky demonstration. Here we introduce the project, presenting preliminary simulation results and detailing the optical bench.

Resolution and sensitivity of the wavefront sensor (WFS) are key requirements for eXtreme Adaptive Optics (XAO) applications. We present a new class of WFSs, the Bi-Orthogonal Foucault-knife-edge (Bi-O edge), that is directly inspired by the Foucault knife-edge test. The idea consists of using a beam-splitter producing two foci, each of which is sensed by an edge with an orthogonal direction to the other. We describe two implementation concepts. The first one, the tip-tilt modulated sharp Bi-O-edge, can be seen as a mild evolution of the Pyramid. The second one uses a smooth, gradual amplitude mask over a ’grey’ zone on the edge (grey Bi-O edge). We analyze the increased gain in sensitivity and the super-resolution capability, we compare these properties to the Pyramid sensor and produce end-to-end simulations. An important advantage of the grey Bi-O edge is the static modulation which is well adapted for fast XAO systems. The grey edge consists of a rectangular zone on the edge of the same size as the modulation circle. We will discuss the manufacturability of loss-less grey Foucault-knife edges, and we develop a polarization-based technique for the Bi-O edge prototype for the ESO GHOST test bench.

We propose a new wavefront sensor with a birefringent point-diffraction interferometer (b-PDI) for extreme adaptive optics and report the experimental results. It has a phase mask made with birefringent crystal TiO₂ and simultaneously generates interferograms with three different phase-shifts. The statistical error of the b-PDI was consistent with a simple error propagation model. The error due to photon noise was 1.4 times larger than that of the Zernike wavefront sensor (ZWFS). The b-PDI could determine the wavefront phase up to ∼1 wavelength without ambiguity. The range is two times larger than that of the ZWFS, which is affected by the ambiguity of the sine of the phase.

The Ingot WFS belongs to a class of pupil-plane WFSs designed to address the challenges posed by Sodium Laser Guide Stars, and consists of a combination of refractive and reflective surfaces, arranged into a complex prismatic shape that extends in three dimensions. Specifically, it leverages the Scheimpflug principle to sense the full 3D volume of such elongated, time-varying sources, thus optimizing the performance of the next-generation AO-assisted giant telescopes. In this work we discuss the geometrical and optical motivations endorsing the development of this class of WFSs, showing the different configurations we propose to the AO community. We also provide a first order comparative analysis with other approaches and review the state-of-the-art of the Ingot project, including improvements made in the laboratory and future milestones.

WIVERN is a testbed for experiments in non-LGS laser-based wavefront sensing, because it is difficult to conceive of wide-field MCAO and MOAO over arcminute scales with good sky-coverage with a practical number of LGS. This presentation focuses on one of two non-LGS concepts we are studying: correlating Shack Hartmann WFS on laser generated speckle. The concept involves projecting random laser speckle into the atmosphere and using Rayleigh back-scattering to re-image the high-contrast pattern in the WFS. WIVERN is designed to emulate laser uplink through the atmosphere, back-scattering from up-to 20km distance, assuming a 8m telescope aperture, and finally reception back at the pupil, via one or two phase screens resulting in 0.8 to 1.6 arcsec seeing. The WFS measurements use both on- and off-axis point sources (emulated NGS) and the re-imaged laser speckle. These are then compared to show the consistency in measured slopes, demonstrating the potential of tomographic sensing with speckle. For context, simulation results that confirm the bench measurements are shown. Finally, the necessary calibration procedure for the DM interaction matrix is described together with initial results.

This paper provides an update on the progress in designing, prototyping, modeling, and manufacturing the TMT first light AO systems and their AO components. Key highlights encompass the completion of the preliminary design of the Laser Guide Star Facility, the fabrication of the NFIRAOS deformable mirrors, the study of the petalling modes impact and associated mitigations for TMT, and the development of the first light verification plan, and assessment of the expected performance.

NFIRAOS (Narrow-Field InfraRed Adaptive Optics System) will be the first-light multi-conjugate adaptive optics system for the Thirty Meter Telescope (TMT). NFIRAOS supports three Near Infrared (NIR) client instruments, and provides exceptional image quality across the 2 arcminute field of view. In 2018, NFIRAOS passed the Final Design Review (FDR), but there have been several substantial changes more recently. The optical enclosure (ENCL) refrigeration design was updated for CO2 refrigerant, and an enclosure wall panel was prototyped. The polar-coordinate CCD for the laser guide star (LGS) wavefront sensor camera was replaced with a commercial C-Blue camera from First Light Imaging. More recently, the NFIRAOS Science Calibration Unit (NSCU), which was previously a separate Canadian contribution, was incorporated into the scope of NFIRAOS, and has progressed to the Conceptual Design level. In addition to these changes, the team has been working to bring the last of the low-risk subsystems to final design level in preparation for the beginning of construction.

HARMONI is the first light visible and near-IR integral field spectrograph for the ESO-ELT. It will consist of a versatile instrument with two adaptive optics (AO) modes: a classical Single Conjugate AO and a Laser Tomography AO. The instrument will cover a large range of science cases from exoplanet imaging to distant galaxies. In this paper, we present the current design of the LTAO mode and its performance analysis to optimize the optical performance of the instrument and maximize the sky-coverage.

MORFEO is a post-focal adaptive optics module that forms part of the first light instrument suite for the Extreme Large Telescope (ELT). The project is now in the Final Design Phase. In this paper, we report the status of the project.

In the past two years significant forward progress has been achieved in development of Adaptive Optics sensing and control technology needed for the observation modes of the Giant Magellan Telescope1. Most notable is the recent progress in demonstrating the accurate and stable control of segment piston in the diffraction-limited Natural Guide Star AO observation mode. Two NSF-funded testbeds have been successfully operated to validate the control algorithms for active optics, adaptive optics and segment piston in diffraction-limited observation. GMTO also built and operated wavefront sensor prototypes and integrated them with the testbeds. The testing has largely validated the wavefront sensor designs and has retired much of the fabrication and assembly risks. In parallel with the hardware demonstrations, significant progress has been achieved in both NGAO and LTAO control simulations verifying compliance with the required performance in each of these observation modes and thereby supporting the image quality budgets. In the area of design the GMTO Telescope Metrology Subsytem has passed its Preliminary Design Review and the conceptual design of the Adaptive Optics Test Camera has been completed. Finally, a Delta Preliminary Design phase for the LTAO hardware has begun.

The Laser Tomography Adaptive Optics (LTAO) system for the Giant Magellan Telescope (GMT) will be the first laser guide star adaptive optics (LGS AO) wavefront control for the GMT, aimed at pushing the boundaries of astronomical observations beyond the limits of natural guide star (NGS) operations. The Australian National University is leading the design of some of the largest work packages in the GMT LTAO project, including the GMTIFS on-instrument wavefront sensor, LTAO LGS wavefront sensors, and the Laser Guide Star System (LGSS). Central to the LTAO system is the Laser Guide Star Subsystem (LGSS), responsible for creating a Laser Guide Star (LGS) asterism adjustable between 25 to 60 arcsec and centred on the science target. The LGSS comprises six Laser Guide Star Units (LGSU), each emitting a laser beam with precise spectro-temporal and spatial characteristics. The LGSU includes a Laser System, a Beam Conditioning and Diagnostic System (BCDS), a Laser Launch Telescope (LLT), and a LGS Unit Control System (LGSU CS). These components collectively ensure accurate pointing and focusing of the laser beam on the sky. This paper provides a comprehensive update on the re-assessment and redesign of the LGSS for the GMT, a collaborative effort reignited at the Australian National University after a ten-year hiatus in design work. The LGSS design is ready to re-attain the Preliminary Design level, after integrating interface changes that have evolved at the telescope since the Preliminary Design Review took place in 2013. In order to take advantage of advances made in the field over the past 10 years, the study investigates the feasibility of a shared launch for the GMT LTAO system and also re-evaluates the number of lasers required to generate the 6 LGS asterism.

The Natural Guide-star Adaptive Optics (NGAO) mode of the Giant Magellan Telescope (GMT) is one of the two diffraction-limited AO modes under development by GMTO and its partner institutions. It will use the Adaptive Secondary Mirror (ASM) for wavefront correction, and a Natural Guide star Wavefront Sensor (NGWS) unit featuring two visible-light sensing channels to measure wavefront aberrations, including phasing errors between the seven segments of the GMT. The first NGWS channel features a modulated pyramid wavefront sensor (PWFS) and the second NGWS channel features a Holographic Dispersed Fringe Sensor (HDFS), which unambiguously detects segment piston errors as large as ~10 microns in wavefront. To test the performance of this novel wavefront sensing architecture, a prototype of the NGWS was built and integrated with the High Contrast AO Testbed (HCAT) and the MagAO-X system in the laboratories of the Center of Astronomical Adaptive Optics (CAAO) of the University of Arizona. The INAF Arcetri AO group designed and built the first NGWS channel, while GMTO designed and built the second NGWS channel in collaboration with CAAO. We report in this contribution the results of the laboratory experiments conducted over two two-week runs held in 2023 that demonstrate the capability of the NGWS to sense and correct for wavefront and phasing errors under the presence of mild atmospheric disturbances using the GMT NGAO control algorithms adapted to the testbed.

ELTs have the potential for imaging reflected light from habitable rocky planets around M-stars. To address that exciting science we present the PDR level optical-mechanical design for a high-contrast coronagraphic instrument for the 25.4m Giant Magellan Telescope (GMT) called GMagAO-X. It is a first light extreme adaptive optics (ExAO) coronagraphic instrument which mounts to the sector D folded port of the GMT. To meet the strict ExAO fitting and servo error requirement (<90nm rms WFE), GMagAO-X must have 21,000 actuator DM capable of >2KHz update speeds. To minimize wavefront/segment piston error GMagAO-X has an interferometric beam combiner on a vibration isolated table, as part of this 21,000 actuator “parallel DM”. Segment/petal piston errors are continuously sensed by a novel Holographic Dispersed Fringe Sensor (HDFS). In addition to a coronagraph, it has a post-coronagraphic Lyot Low Order WFS (LLOWFS) to sense non-common path (NCP) errors. The LLOWFS drives a non-common path DM (NCP DM) to correct those NCP errors. GMagAO-X obtains high-contrast science and wavefront sensing in the visible or the NIR. Here we present our successful, externally reviewed (Feb. 2024), PDR optical-mechanical design that satisfies GMagAO-X’s top-level science requirements and is compliant with the GMT instrument requirements/ICDs and only requires COTS parts and readily available 2-5 inch sized optics. We have also prototyped the parallel DM and the HDFS phasing sensor on the HCAT testbed. We show initial phased HCAT testbed results for the parallel DM and initial on-sky phasing results for HDFS.

METIS, the Mid-infrared ELT Imager and Spectrograph, will be one of the first instruments to be used at ESO’s 39m Extremely Large Telescope (ELT), that is currently under construction. With that, a number of firsts are to be addressed in the development of METIS’ single-conjugate Adaptive Optics (SCAO) system:

• the size of the telescope and the associated complexity of the wavefront control tasks

• the unique scientific capabilities of METIS, including high contrast imaging

• the interaction with the newly established, integrated wavefront control infrastructure of the ELT

• the integration of the near-infrared Pyramid Wavefront Sensor and other key Adaptive Optics (AO) hardware embedded within a large, fully cryogenic instrument.

METIS and it’s AO system have passed the final design review and are now in the manufacturing, assembly, integration and testing phase. The firsts are approached through a compact hard- and software design and an extensive test program to mature METIS SCAO before it is deployed at the telescope. This program includes significant investments in test setups that allow to mimic conditions at the ELT. A dedicated cryo-test facility allows for subsystem testing independent of the METIS infrastructure. A telescope simulator is being set up for end-to-end laboratory tests of the AO control system together with the final SCAO hardware. Specific control algorithm prototypes will be tested on sky. In this contribution, we present the progress of METIS SCAO with an emphasis on the preparation for the test activities foreseen to enable a successful future deployment of METIS SCAO at the ELT.

MICADO is the ELT first light instrument, an imager working at the diffraction limit of the telescope thanks to two adaptive optics (AO) modes: a single conjugate one (SCAO), available at the instrument first light and developed by the MICADO consortium, and a multi conjugate one (MCAO), developed by the MORFEO consortium. Although the project final design review process is about to be completed, the review board and ESO acknowledged that "the review of the final design can be considered complete for the majority of the MICADO sub-systems" and agreed that MICADO can start manufacturing. For the MICADO SCAO module, we have started the manufacturing of several parts: the majority of the SCAO optics and of the SCAO mechanics, the real-time computer software and the instrument control software. This manufacturing is ordered in several steps to allow the progressive integration of a first full AO close loop with the final SCAO parts. In this contribution, we will focus on the first two steps: on our AO Sésame bench and the so-called "β flat configuration". We will present the status of this manufacturing and the first results obtained.

MICADO SCAO RTC hard real-time capabilities are provided by COSMIC, while the soft real-time features rely on the ESO RTC Toolkit. The RTC has actively begun the MAIT phase. For this purpose, a full-scale setup has been assembled to start the integration of the S-RTC and H-RTC. The setup is used with an additional simulation node running either COMPASS or ESO WFS simulator, allowing to validate the various implementations of the RTC in terms of AO performance and latency requirements. On top of that, an instance of the RTC has been deployed on the SESAME bench at LESIA. This paper will present the MICADO SCAO RTC architecture after final design review, the design choices and the current status of the MAIT activities related to the RTC. It will provide an overview of the H-RTC pipeline design, including performance benchmark and validation through simulation mode and on-bench results. It will also picture the current status of the RTC Toolkit integration activities for the S-RTC on multi-nodes cluster including the first implementation of telemetry consumption, data tasks, data storage, data visualization, H-RTC optimization and automation mechanisms.

The Herzberg Extensible Adaptive Real-time Toolkit (HEART) is a collection of libraries and other software components developed at the Herzberg Astronomy and Astrophysics Research Centre (HAA) to control multiple types of Adaptive Optics (AO) systems. The HEART RTC design has two main components: the Hard Real-Time RTC (HRT), which includes all the time-critical high-speed processing tasks; and the Soft Real-Time RTC (SRT), which includes the nontime critical tasks such as optimizations, AO parameter updates, and diagnostics. HEART was used to create the REVOLT RTC (Research, Experiment, and Validation of Adaptive Optics with a Legacy Telescope), a single conjugate AO (SCAO) system, for the HAA’s 1.2-m telescope. This paper presents significant aspects of HEART that were successfully tested with REVOLT, either in the daytime testing or on-sky. Highlights include specialized functionality of the HRT such as uncontrolled mode cleanup, power spectra of the high-order vector, and pseudo-open loop feedback. Also highlighted are the recent design of the ELT Andes (ArmazoNes high Dispersion Echelle Spectrograph) SCAO RTC, which is a pixel based reconstructor. Core SRT operations such as reconstructor generation and optimization were also demonstrated. Presentation of results from these test runs make use of our HEART Analysis (HEART-ANA) package.

The COSMIC platform endeavors to establish a potent, versatile, and accessible AO RTC platform for the AO community. This joint project allies the Observatoire de Paris with the Australian National University (ANU), and relies on the CACAO software, a creation of the Subaru Telescope. Although the primary intended use was for the ELT AO instrument, the platform now accommodates several systems on different scales. The effectiveness of COSMIC in current and future AO systems has already been proven. The current progress on the COSMIC platform extends beyond, with technical solutions offered for various applications other than AO such as embedded systems, radio astronomy, and radar. This interest exhibited by other communities has initiated new collaborations and additions to the platform, which might appeal to the AO community. This paper presents the current state of the COSMIC platform, including ongoing developments and future perspectives. One recent development is heterogeneous computation which allows for a hardware-agnostic real-time pipeline, thereby enabling the deployment of an AO pipeline on both CPU and GPU, irrespective of the vendor (NVIDIA or AMD). Another contribution involves the porting of COSMIC onto an NVIDIA Jetson Xavier, effectively paving the way for embedded system applications. As artificial intelligence is rapidly gaining importance in the AO community, efforts have been made to incorporate machine learning inference into the real-time critical path. Additionally, a collaboration with the radio astronomy community has led to a significant contribution towards efficient real-time data ingestion at a high volume. This paper aims to illustrate these achievements and demonstrate their potential applications within the AO community.

Adaptive optics systems are usually prototyped in a convenient but slow language like MATLAB or Python, and then re-written from scratch using high-performance C/C++ to perform real-time control. This duplication of effort adds costs and slows the experimentation process. We present instead a technical demonstration of performing real time, sub-millisecond latency control with an adaptive optics system using the high-level Julia programming language. This open-source software demonstrates support for multiple cameras, pixel streaming, and network-transparency distributed computing. Furthermore, it is easy to interface it with other programming languages as desired.

Robo-AO was the first fully automated astronomical adaptive optics (AO) system, and was able to complete surveys of stellar objects in a fraction of the time of other AO systems. Two new robotic AO systems build on the heritage of Robo-AO. Robo-AO 2 is a site optimized system for the U. Hawai'i 2.2-m telescope on Maunakea, with an improved design and better sensitivity it will be able to continue the high cadence, high resolution observations that Robo-AO pioneered. SIGHT will be installed on the Palomar 200-inch telescope, and is designed to improve the delivered image quality to instruments at the Cassegrain focus (initially it will feed the Next Generation Palomar Spectrograph); the goal is to decrease the seeing by half. The two instruments have different science goals and performance requirements, but they share a common software architecture that allows the flexibility to do fully autonomous observations in these far different regimes. This presentation will discuss the development of the Robo-AO architecture and the evolution of that software into a more flexible system that can underpin the operation of different AO systems while still delivering fully autonomous capability.

The next generation of Extremely Large Telescope (ELT, 24 to 39m diameter) will suffer from the so-called ”pupil fragmentation” problem. Due to their large spiders, differential pistons will appear in the wavefront between the part of the pupil separated by the spiders during observations. The Adaptive Optics (AO) system necessary to compensate atmospheric turbulence appears unable to sense this differential piston leading to bad control by the loop. Hence, such differential pistons, a.k.a petal modes, will prevent the AO system from reaching the diffraction limit of the telescope and ultimately will represent the main limitation of AO-assisted observation with an ELT and will be particularly detrimental to High Contrast observation modes. All the future single conjugated AO systems for the ELT have a Pyramid Wavefront Sensor (PyWFS) which can be sensitive to the petal mode if unmodulated. But the current control methods available forces the modulation of the PyWFS to ensure the AO loop stability. In this presentation we study the origin and properties of the petal mode through a simplified pupil. There are two identified sources: the atmospheric turbulence and the Low Wind Effect (LWE). We show how the atmospheric turbulence can be mitigated though minioning and the limit of this mitigation with the origin of the petal flares. Furthermore, the minioning is inefficient at reducing LWE petal. This has led to the necessity of a second sensor dedicated to the petal mode measurement: a petalometer. We finally propose a PyWFS type of petalometer and study its properties and limits for the control of the petal mode.

Petalling modes characterize the differential piston between the petals of the telescope’s aperture, typically separated by the secondary mirror support spiders. Since the discovery of petalling modes by the VLT in low wind conditions, addressing these modes has become a focal point, pertinent to nearly all telescopes equipped with high-performance adaptive optics systems. These modes are poorly sensed by mainstream wavefront sensors (WFS). There are three primary factors contributing to petalling modes in general. Firstly, turbulence discontinuity occurs across the spiders due to temperature non-uniformity, particularly in low wind conditions. This issue is partly mitigated by applying low emissivity coating, pioneered by the VLT. Computational fluid dynamics models used to assess the dome seeing aid in quantifying the residual effect. Secondly, phasing and stacking errors may arise in segmented mirrors. For TMT, the impact is negligible owing to the small width of the support spiders (22.5 cm) and highly redundant phasing sensors in the Alignment and Phasing System. Lastly, measurement noise may propagate to these modes, which we have observed when controlling two deformable mirrors in classic adaptive optics (AO) mode with a single pyramid WFS. Employing modal control with truncated modes is a simple and effective mitigation strategy without a notable performance penalty. Nevertheless, having a mechanism that can measure and control the petalling modes will provide reassurance of the AO system’s performance. In this paper, we present a novel hybrid iterative petalling sensor (HIPS) that utilizes modal based phase retrieval on time averaged PSFs from diffraction-limited tip/tilt/focus and full aperture low-order wavefront sensors, which breaks the even mode ambiguity. We successfully demonstrated this algorithm in both static and end-to-end closed-loop AO simulations.

The petaling effect, induced by pupil fragmentation from the telescope spider, drastically affects the performance of high contrast instruments by inducing core splitting on the PSF. Differential piston/tip/tilt aberrations within each optically separated fragment of the pupil are poorly measured by commonly used Adaptive Optics (AO) systems. We here pursue a design of dedicated low-order wavefront sensor – or petalometers – to complement the main AO. Interferometric devices sense differential aberrations between fragments with optimal sensitivity; their weakness though is their limitation to wrapped phase measurements. We show that by combining multiple spectral channels, we increase the capture range for petaling aberrations beyond several microns, enough to disambiguate one-wave wrapping errors made by the main AO system. We propose here to implement a petalometer from the multi-wavelength imaging mode of the VAMPIRES visible-light instrument, deployed on SCExAO at the Subaru Telescope. The interferometric measurements obtained in four spectral channels through a 7 hole non-redundant mask allow us to efficiently reconstruct differential piston between pupil petals.

Scientists at the Starfire Optical Range (SOR) have been researching Rayleigh beacons and mesospheric sodium beacons for adaptive optics (AO) for nearly three decades. We developed four different sodium-wavelength lasers, all of which were based on diode-pumped, sum-frequency Nd:YAG oscillators. In 2016, we combined light from two commercial 22-watt, sodium-wavelength lasers to form a single beacon. These commercial lasers, which use resonant-frequency doubling of light from a Raman fiber-amplifier, were built by MPB Communications and Toptica Projects. In 2019, we started to develop and procure a 75-watt sodium-wavelength laser to enable better correction of turbulence in poor seeing. In conjunction with Toptica Projects and European astronomers, we have increased the return flux from sodium beacons by shifting or chirping the laser wavelength to compensate for recoil of optically pumped sodium atoms. In addition, we have demonstrated a single-sideband D2b re-pumper. In this talk, we review the development our new sodium beacon laser and discuss results from an on-sky test in 2023 that demonstrates the improvement in beacon brightness by using these techniques.

Remotely pumped by a single-mode, polarization-maintaining (PM) 1120-nm fiber laser, a single-frequency linearly-polarized 1178-nm Raman fiber amplifier (RFA) has been developed with a maximum continuous-wave (CW) output power of 130-W. This remotely-pumped high-power RFA system features the same modular, compact and ruggedized design as the proven SodiumStar 20/2 and provides the potential for a guide star laser with a 589-nm output power approaching 100-W, assuming a 10 to15% D2b sideband content and a typical overall conversion efficiency of a resonant second harmonic generator of ~ 70%. Utilizing innovative patented remote pump delivery technology, the 589-nm laser head (LH), which includes the RFA itself, can now be separated physically from the electronics cabinet (EC), which hosts the bulky and heat-generating control electronics, the 1178-nm seed laser, the fiber laser power supply and the fiber laser pump module. The physical separation distance from the LH to the EC can now be as long as 30-m for a 130-W RFA and up to 50-m for a 100-W RFA. The remote pumping capability of this high-power RFA offers important system configuration flexibility and is well-suited for laser guide star assisted adaptive optics systems in ground-based large-aperture astronomical telescopes, optical ground stations and space debris tracking systems, particularly when the available laser launching platform space is strictly limited.

In ground-based astronomy, the ability to couple the light into single-mode fibers (SMFs) is limited by atmospheric turbulence, which prohibits the use of many astrophotonic instruments. We propose a silicon-on-insulator photonic chip capable of coherently coupling the out-of-phase beamlets from the subapertures of a telescope pupil into an SMF. The PIC consists of an array of grating couplers used to inject the light from free space into single-mode waveguides on a chip. Metalic heaters modulate the refractive index of a coiled section of the waveguides, facilitating the co-phasing of the propagating modes. The beamlets can then be coherently combined to efficiently deliver the light to an output SMF. In an adaptive optics system, the phase corrector would act as a deformable mirror commanded by a controller that takes phase measurements from a wavefront sensor. We present experimental results for the PIC tested on an AO testbed and compare the performance to simulations.

Since the early 1980s, the Institute of Optics & Electronics (IOE) at Chinese Academy of Sciences (CAS) has accumulated over 40 years of expertise in the research and development of piezoelectric deformable mirror (DM) technologies. This institution has successfully implemented several piezoelectric DMs in diverse application systems. The following paper will outline the historical background of piezoelectric DM technologies at IOE, highlight some recent achievements, and elaborate on the key features, performances, and testing results of these DMs. Specifically, it will cover:1). A high-order DM equipped with 913 actuators; 2).The 2nd generation piezoelectric deformable secondary mirror (PDSM) featuring 241 actuators; 3).A high-density DM boasting over 1000 actuators. Moreover, the paper will discuss the advancements made in the development of higher-order DMs and PDSMs at IOE, CAS.

The two Large Binocular Telescope (LBT) Adaptive Secondary Mirror (ASM) units have been operating successfully since their installation in 2010/2011. Since that time, the two units have accumulated >25 years of combined operation on the telescope, which is remarkable given that these mirrors employ a relatively new technology. In this paper we will report statistics related to the operation of the LBT ASMs, including the operation time and down time, number and frequency of failing actuators and periodic maintenance campaigns. We will discuss the two main operational modes of these mirrors (seeing limited and AO operation) and the achieved performances, such as mirror optical flat and optical calibration quality, as well as the effect of telescope operational conditions such as: environmental conditions, telescope pointing and wind conditions; in particular, the wind effects and their implications, which drive some of the design requirements, will be reviewed and extensively discussed for the first time. Finally, we will report on the recent recoating of one of the three thin shells, which was done with a new and improved method. In comparison this new method is more safe, more reliable and less time consuming. We will describe the new hardware used for the thin shell coating and its interfacing to the ASM units as well as the procedural changes implemented.

The 25.4m diameter Giant Magellan Telescope utilizes a segmented adaptive secondary mirror subsystem (ASMS) for correction of atmospheric wavefront error (r0=7cm), wind-induced telescope vibrations up to 17m/s wind speed, and M1 and M2 segment alignment errors. The ASMS is composed of seven ASM segments. Each is a 1.05m diameter concave circular segment with a 2mm thick face sheet that is driven by 675 voice coil motor motors to provide wave front and phasing control. The face sheet surface figure can be updated at up to 2kHz with a -3dB bandwidth greater than 800Hz. The ASMS is integrated to the top end of the telescope by actively controlled 6 DOF hexapods. Each hexapod provides 7Hz position control to maintain the alignment within the capture range of the wave front control system. The first off-axis ASM segment is currently being manufactured by the AdOptica Consortium and their subcontractors. The Zerodur Reference Body, Zerodur face sheet, and major structural components have been manufactured and integrated. Structural and dynamic testing of the ASM primary load path has been completed. A phasing testbed is in the build stage that utilizes the single ASM segment, edge sensors, and a reference frame to simulate the phasing of an array of 4 ASM segments. This document presents an overview of the ASMS design and the results of the manufacturing, assembly and testing of the first ASM segment.

The Keck Adaptive Secondary Mirror (KASM) project is planned as a core component of adaptive optics (AO) improvements for the Keck 1 telescope. KASM will provide image quality enhancements to all instrument locations, while also enabling correction of the ground layer turbulence for wide field instruments, and the foundation for a visible light diffraction-limited AO system. KASM is intended to replace the original telescope secondary mirror (M2) and will support both adaptive optics correction and purely passive (seeing-limited) observing modes of operation. The concept for KASM has been developed considering both voice coil and hybrid variable reluctance actuator technology. A metrology and calibration setup for off-sky use has been developed to verify KASM performance both prior to installation and once at the telescope.

We are developing an adaptive secondary mirror (ASM) that uses a new actuator technology created by the Netherlands Organization for Applied Scientific Research (TNO). The TNO hybrid variable reluctance actuators have more than an order of magnitude better efficiency over the traditional voice coil actuators that have been used on existing ASMs and show potential for improving the long-term robustness and reliability of ASMs. To demonstrate the performance, operations, and serviceability of TNO’s actuators in an observatory, we have developed a 36-actuator prototype ASM for the NASA Infrared Telescope Facility (IRTF) called IRTF-ASM-1. IRTF-ASM-1 provides the first on-sky demonstration of this approach and will help us evaluate the long-term performance and use of this technology in an astronomical facility environment. We present calibration and performance results with the ASM in a Meniscus Hindle Sphere lens setup as well as preliminary on-sky results on IRTF. IRTF-ASM-1 achieved stable closed-loop performance on-sky with H-band Strehl ratios of 35-40% in long-exposure images under a variety of seeing conditions.

The well consolidated technology developed by AdOptica for large, contactless deformable mirrors is now being evolved to higher actuator density and low power consumption. In this paper we present the simulation of the performances of an 800mm deformable mirror with 2172 actuators and the 246mm diameter prototype with 169 actuators, currently in construction. The proposed design features low power dissipation and all the major characteristics our baseline technology, including the large stroke also in tip-tilt and piston, the high static accuracy and the capability to operate with several failed actuators. Typical applications include daytime turbulence compensation with field stabilization and large post focal deformable mirrors for high order correction.

Tomographic reconstruction at ELT scales requires knowledge of the high resolution optical turbulence profile Cn2(h). While in most cases this will be obtained through analysis of the AO telemetry, it is also important to have an independent site monitor that is capable of verifying these profiles, or providing profiles to "cold start" the system at the beginning of an observation. Here, we present the initial results of the pt5m-SCIDAR, a generalised-SCIDAR instrument operating on the robotic point-5 metre (pt5m, D=0.5m) telescope in La Palma. We show that despite the small aperture we are able to extract around 15-layer Cn2(h) profiles and explore the results of measurement campaigns with comparison to other site monitors around the observatory. We believe SCIDAR on smaller telescopes such as the pt5m presents a cost-effective solution as a site monitor for the Cn2(h) profile with sufficient resolution to support ELT tomography.

In this contribution we report the on-going progresses of the project FATE, an operational automatic forecast system conceived to deliver forecasts of a set of astroclimatic and atmospheric parameters having the aim to support the science operations (i.e. the Service Mode) at the Very Large Telescope. The project has been selected at conclusion of an international open call for tender opened by ESO and it fits with precise technical specifications. In this contribution we will present the ultimate goals of this service once it will be integrated in the VLT operations, the forecasts performances at present time and the state of the art of the project. FATE is supposed to draw the roadmap towards the optical turbulence forecast for the ELT.

A six-night optical turbulence monitoring campaign has been carried at Cerro Paranal observatory in February and March, 2023 to facilitate the development and characterisation of two novel atmospheric site monitoring instruments - the ring-image next generation scintillation sensor (RINGSS) and 24-hour Shack Hartmann image motion monitor (24hSHIMM) in the context of providing optical turbulence monitoring support for upcoming 20-40m class telescopes. Both instruments offer the potential to replace the outdated MASS-DIMM, utilising new technologies to produce detailed, real-time characterisation of optical turbulence conditions at a site. In addition, the well-characterised Stereo-SCIDAR and 2016-MASS-DIMM were both active throughout the campaign providing further data for comparison. Contemporaneous measurements of both the integrated turbulence parameters - including seeing, free atmosphere seeing, coherence time and angle – and the vertical optical turbulence profile are examined along with the first 24-hour, day and night turbulence measurements at the site.

Estimating turbulence parameters is essential during commissioning and optimising adaptive optics or fringe tracking systems. It also gained new relevance with free-space optical communication applications. The estimation of such parameters is done under the assumption of stationarity. Yet, the stationarity time scale of the atmospheric turbulence is unknown. The breakdown of this assumption leads to incorrect estimates and added error terms. In this paper, we illustrate stationarity detection with unit root testing and the pitfalls of its application to turbulence parameter time series.

In the upcoming generation of Extremely Large Telescopes the impact of the turbulent atmosphere is corrected by Adaptive Optics (AO) system. However, the quality of astronomical images is still degraded due to the time delay stemming from the wavefront sensor integration time and adjustment of the deformable mirror (DM). This results in a blur which can be mathematically described by a convolution of the original image with the PSF of the instrument, telescope and residual atmospheric perturbations. The PSF of an astronomical image varies with the position in the observed field, which is a crucial aspect in observations on ELTs. We adapted existing techniques to reconstruct the PSF from telemetry data to make them feasible for the needs of MICADO and MORFEO. In particular, we use an approach for atmospheric tomography with a time series of AO telemetry data in SCAO mode. In MCAO mode, we use a tomographic reconstruction as performed within the RTC. Our results are obtained for a simulated ELT setting in Octopus and Compass, as well as for on-sky data from ERIS@VLT. We further discuss the implementation strategy in order to have a computational and memory efficient software.

High-contrast imaging data analysis depends on removing residual starlight from the host star to reveal planets and disks. Most observers do this with principal components analysis (i.e. KLIP) using modes computed from the science images themselves. These modes may not be orthogonal to planet and disk signals, leading to over-subtraction. The wavefront sensor data recorded during the observation provide an independent signal with which to predict the instrument point-spread function (PSF). MagAO-X is an extreme adaptive optics (ExAO) system for the 6.5-meter Magellan Clay telescope and a technology pathfinder for ExAO with GMagAO-X on the upcoming Giant Magellan Telescope. MagAO-X is designed to save all sensor information, including kHz-speed wavefront measurements. Our software and compressed data formats were designed to record the millions of training samples required for machine learning with high throughput. The large volume of image and sensor data lets us learn a PSF model incorporating all the information available. This allows us to probe smaller star-planet separations at greater sensitivities, which will be needed for rocky planet imaging.

To facilitate easy prediction and estimation of adaptive optics performance, we have created a fast algorithm named TipTop. This algorithm generates the expected AO point spread function (PSF) for any existing AO observing mode (SCAO, LTAO, MCAO, GLAO) and any set of atmospheric conditions. Developed in Python, TipTop is based on an analytical approach, with simulations performed in the Fourier domain, enabling very fast computation times (less than a second per PSF) and efficient exploration of the extensive parameter space. TipTop can be used for several applications, from assisting in the observation preparation with the exposure time calculator (ETC), to providing PSF models for post-processing. TipTop can also be used to help users in selecting the best NGSs asterism and optimizing their observation. Over the past years, the code has been intensively tested against other simulation tools, showing very good agreements. TipTop is also currently deployed for VLT instruments, as proof of concepts in preparation of the ELT. The code is available here: https://tiptop.readthedocs.io/en/main/, and we encourage all future observers of the ELT to test it and provide feedback.

AOC (Adaptive Optics system at Calern) is an adaptive optics bench being developed on the Epsilon (East) telescope of the two 1m telescopes of C2PU (Centre Pédagogique Planète Univers), Calern observatory, Observatoire de la Côte d'Azur (OCA), near Nice (France). It is installed at the F/35 Coudé focus, and aims at correcting the wavefront in the visible and in the near-infrared, using an ALPAO 11x11 actuator-across deformable mirror feeding a 10x10 Shack-Hartmann wavefront sensor. It is currently being upgraded with a First Light Imaging OCAM2 EMCCD detector, which will allow us to increase the number of available pixels per sub-aperture and the loop frequency, as well as to take advantage from a negligible read-out. The system is designed to work both in a standard stellar mode and in a more innovative planetary mode, capable of operating on planets such as Mars, Saturn and Jupiter, with a field up to 60arcsec. Such a wide field is much larger than the isoplanatic angle, therefore only the turbulent ground layer can be corrected, up to an altitude of a few thousand meters. Extensive simulations have been carried out of these two different modes. The system is now undergoing implementation and validation using a low order modal control (10 to 16 modes), but a zonal control will be implemented next to ensure performance improvement down to λ∼500nm. The loop frequency was limited to 500Hz by the speed of the Andor iXon camera, but its replacement by an OCAM2 camera will allow to reach between 1.5 and 2.2kHz (depending on binning). Theoretical performance of the system has been studied through simulations for the planetary mode and presented previously at SPIE. Here we present the implementation of the system and its preliminary performance on the sky and comparison with the simulations. In the future, we plan to better characterize the temporal transfer function as a function of the gain and the number of corrected modes, in order to implement an automatic gain control, both zonally in the visible and modally for near infrared applications. We are also implementing a control of the non-common path aberrations (NCPA). This is done by analysing the aberrations on a defocused stellar image, using the DONUT algorithm. We intend to characterize these NCPA in real-time directly from the observations. We also consider parameterizing the resulting point-spread function from the real-time statistics of the adaptive optics system to be used for further data analysis.

The MAVIS instrument (MCAO-Assisted Visible Imager and Spectrograph), designed for visible light observations, is a significant advancement in adaptive optics technology. To rigorously test MAVIS and ensure its smooth on-sky performance, we have developed a dedicated Verification Test Bench (VTB). The VTB serves as an internal tool during the Assembly, Integration, and Testing (AIT) phase, and is crucial in conducting essential tests related to wavefront error correction via a ground-conjugated deformable mirror. In this work, we provide brief descriptions of the foreseen tests for MAVIS that require the use of the VTB. A particular focus of the study is dedicated to the preliminary design of the VTB. We present the optomechanical implementation envisaged for it, emphasising system requirements and optical design constraints.

Quantum Key Distribution (QKD) is a cryptography technique that allows two parties to share a secret common key that can be used for a secure exchange of information. To meet the requirements and interests of different final users, the technological development of this technique has rapidly led toward commercial systems for a global quantum infrastructure, namely a quantum network. Communication among parties requires an optical channel, which for short distances is typically provided by optical fiber. However, the limitation of optical losses on longer fiber links, or the unavailability of an exploitable deployed fiber, requires the use of a different QKD medium, i.e. free-space. At the University of Padova we are investigating, both theoretically and experimentally, how Adaptive Optics (AO) can be used to improve the performance of free-space quantum communication, with a particular focus on QKD. Following our theoretical studies on the optimal design for an intermodal free-space/ fiber link, we were able to realize different QKD field trials along a 600m-long free-space link exploiting polarization encoding. Besides the metropolitan area of Padova, we are now working on the development of an extra-urban free-space link, which is more prone to atmospheric turbulence effects. For this link, we equipped a radar tower located on a hill in Teolo with a remotised optical transmitter, and we are now developing the AO system for the receiving telescope, located at the Department of Information Engineering in Padova, with which we plan to realize QKD during day and night time.

In the upcoming future the Adaptive Optics group of the Arcetri Observatory aims to integrate and operate two laboratory R&D facilities dedicated to explore new technologies for the operation of the next generation of 40m-class telescopes. In a nutshell they are aimed to: 1) to investigate the benefits of a dual-stage AO system for planet finding instruments (like ELT/PCS) and 2) the identification of a suitable sensor for the control of the piston error on the ELT and GMT. The participation of the Arcetri AO group to the STILES project granted the necessary funding and the perfect time frame to procure the key components required to implement these two facilities. In this paper we will introduce the two R&D facilities, detailing their layout in the laboratory and addressing the specific test cases they will be able to mimic for (e.g. sources, atmospheric conditions, telescope degrees-of-freedom, . . . ). We will then focus on the design of 2 key components of the benches: the custom-made segmented mirror for the AoPetalometer bench and the pyramid wavefront sensors for the AoCascading bench.

ULTIMATE-START, designed for the Subaru Telescope, is a laser tomographic adaptive optics (LTAO) system that uses four Laser Guide Stars (LGSs) and four Shack-Hartmann wavefront sensors (SH-WFSs) to perform tomographic wavefront reconstruction towards the astronomical target of interest. The laser launching system splits a single 22W laser beam into four using beam splitters and controls the LGS asterism diameter with a pair of tip/tilt mirrors for each. A Python-based ray-tracing program has been developed to simulate flexible manipulation of the LGS asterism configuration and to predict optical vignetting in the laser beam at the exit of the Laser Launching Telescope (LLT). The output of the ray-tracing program is used to simulate the uplink propagation of the laser beam to predict the spot size in the sodium layer. The downward propagation toward the SH-WFS of ULTIMATE-START is then calculated using the simulated laser spot irradiance in the sodium layer. In this paper, we describe the model of the optical system to generate the 4 LGSs and present results of the simulations to predict the properties of the LGS as seen by the wavefront sensor. We also compared the simulation results with the on-sky data obtained with a Shack-Hartmann wavefront sensor attached to the Subaru telescope to validate our method.

Detecting and characterizing Earth-size exoplanets by imaging around Sun-like stars to search for life signatures is a monumental challenge, requiring advanced coronagraph designs and picometer-level wavefront control to achieve 10¹⁰ contrast at separations of only a few lambda/D. While a dedicated space observatory may be required to achieve such extreme observations, a new concept is presented to achieve an intermediate sky-limited 10⁸ visible-band contrast using ground-based 8 to 30m class telescopes. STARLITE (Superluminous Tomographic Atmospheric Reconstruction with Laser-beacons for Imaging Terrestrial Exoplanets) consists of a satellite constellation located on a highly-elliptical, 350, 000km apogee orbit that will allow ∼hours-long observations of astronomical targets. When the constellation surrounds a target, the onboard laser on each satellite will generate extremely bright unresolved off-axis guide stars for adaptive optics, with an exoplanet imaging goal to reach closed-loop Angstrom-level residuals on a science target. In this paper I will present preliminary end-to-end simulations of a five laser-beacon optical system through the atmosphere to estimate the wavefront reconstruction accuracy towards a science target.

The Subaru laser guide star system has been upgraded by implementing the TOPTICA/MPBC guide-star laser and a new mirror-based laser relay system. The upgrade is to replace the aged laser and its transfer system and provide the improved performance for stable science operation. The increased laser return photon can also bring a new capability of generating multiple laser guide stars (LGSs) by splitting the laser beam. The new laser guide star system was installed on the Subaru telescope in December 2021 and commissioning observations were conducted in 2022. The LGSAO mode with the new laser guide star system has been offered for science open use program since 2023. The new laser guide star system provides more stable LGS than the previous system with respect to the laser power and pointing. The LGS spot size is ∼1.0 arcsec in FWHM under median seeing condition. The LGS photon return is more than 10 times brighter than the previous system. By utilizing the increased brightness, further upgrade of the Laser Launching Telescope (LLT) is being implemented to generate the asterism of four LGSs with the diameter variable between 10 and 40 arcsec for the new Laser Tomography Adaptive Optics (LTAO) system.

The Ground Layer Adaptive Optics (GLAO) system is a pivotal component of ULTIMATE, the next-generation instrumentation program for the Subaru Telescope. This collaborative effort led by the Subaru Telescope and the National Astronomical Observatory of Japan, involves Tohoku University, Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), and the Australian National University (ANU). ANU is spearheading the design of the Laser Guide Star Facility (LGSF) and Wavefront Sensor work packages. The GLAO LGSF comprises two Sodium guidestar lasers, each of them splits into two beams, creating an asterism of four artificial stars in the Hawaiian skies. Organized into beam transfer optics, beam diagnostics, and beam projection subsystems, the GLAO LGSF is responsible for conditioning, splitting, and steering laser beams, optimizing their launch configuration over a 20 arcmin on-sky patrol field. We have investigated the expected photon return availability from the GLAO Laser Guide Star Facility (LGSF) on Maunakea, building upon previous studies conducted by our ESO colleagues in Paranal. This analysis incorporates statistics on sodium content and atmospheric parameters, including sodium abundance derived from LIDAR measurements near Sao Paulo, Brazil, semi-empirical models of sodium monthly variation tailored to Maunakea, and measurements of sodium column abundance from our ESO colleagues. In challenging scenarios, including large zenith angles, low sodium abundance, northern telescope pointing, and poor seeing conditions, the return flux may significantly decrease, potentially rendering it insufficient for certain observing cases. We present the impact of sodium photon return availability on ULTIMATE-Subaru science cases, along with variables to consider when designing the next-generation Laser Guide Star Facilities.

We will present the concept of Ground Layer Adaptive Optics the Ritchie-Chrétien telescope Zeiss-2000 (F/8), operated at the Institute of Astronomy of the Russian Academy of Sciences. To correct the tip-tilt of the wavefront, we will use NGS. To do this, it is planned to place a separate tracking camera in the wide field of view of the telescope. To correct the slopes, we will use a deflector equipped with an electronic damping system, which allows us to stabilize the responses of the mirror surface. Rayleigh LGS will be used to correct atmospheric aberrations of higher orders. In order to expand the field of anisoplanatism, we plan to perform spatial modulation of the LGS signal in accordance with scientific goals. Synchronization of the spatial modulator and the Shaсk-Hartmann wavefront sensor with an electro-optical shutter will allow this to be done. The article presents options for the layout of the system, taking into account the preservation of the optical axis of the telescope for attachments.

ULTIMATE-Subaru is the next-generation facility instrument project at the Subaru Telescope, Hawaii. One of its key development components is Ground Layer Adaptive Optics (GLAO), which improves image performance at the K-band by a factor of ∼ 2 compared to seeing conditions over a wide field of view of 20 arcmin in diameter. In the GLAO system, the Wavefront Adaptor Flange including four laser guide star wavefront sensors (LWFS) and four natural guide star wavefront sensors (NWFS) is mounted at the Cassegrain focus of the Subaru Telescope to measure the wavefront by ground layer turbulence. The LWFS and NWFS can move to select stars in 2 to 10 arcmin and 7 to 10 arcmin from the centre of the field of view, respectively, while accommodating effects from the field curvature and non-telecentricity of the telescope. Prototyping activities of the wavefront sensor system are ongoing at the Australian National University (ANU). Single LWFS and single NWFS are assembled and optically aligned in the laboratory to test optical and mechanical performances. To make the simulated source representative of the telescope’s off-axis beams both in terms of the incoming angle and the position of the focus, we also manufacture a prototype of the star simulator, which introduces a set of artificial sources to calibrate encoders of the wavefront sensor mechanisms. In this presentation, we provide an overview of the GLAO wavefront sensor system, the prototyping activities carried out in the ANU laboratory with their purposes and procedures.

The GNAO facility is an upcoming adaptive optics (AO) system for the Gemini North Telescope. It will deliver both wide and narrow field AO capabilities to its first light instrument GIRMOS. GIRMOS is a multi-object AO (MOAO) instrument that houses four near infrared (NIR) IFU spectrographs and a NIR imager similar to GSAOI at Gemini South. The required sensitivity of the combined system is largely driven by rapid transient follow-up AO-corrected Imaging and the required sensitivity is in part driven by the performance of the AO system. Up until recently, the estimated AO performance feeding the combined GNAO+GIRMOS imaging system was derived from models using limited information on what the actual parameters will eventually be. However, the AO system (currently called the AO Bench, or AOB) recently underwent a competitive bidding process to derive an AO design that met or exceeded our AO requirements. This work summarizes the update to the combined GNAO+GIRMOS imaging system performance based on the newly designed AOB parameters. We discuss the impact due to the changes in performance, specifically with respect to key science cases of the GNAO+GIRMOS imaging system compared to the previous models of the AO system. We also discuss the largest hurdles in terms of parameters that affect performance, such as telescope vibrations and detector quantum efficiency and our plans for mitigation.

The Evanescent Wave Coronagraph (EvWaCo) exploits the frustration of the total internal reflection (FTIR) between a prism and a lens put in contact. The starlight is transmitted through the contact area while the light from the companion is reflected. An EvWaCo prototype, equipped with an adaptive optics (AO) system, will be installed at the 2.4m Thai National Telescope as an on-sky demonstrator of the EvWaCo mask’s achromatic capabilities while testing new AO control techniques. To characterize the Extreme Adaptive Optics System (XAO) for this prototype, we developed a bench equipped with a DM192 ALPAO deformable mirror, a 15×15 sub-apertures Shack-Hartmann wavefront sensor (SH-WFS), and a two-track phase plate simulating an average seeing of 1.4" at the Thai National Telescope, and the best seeing at 1.00". Following our previous communications on the characterization of the DM and the phase plate, we present how we calibrate the sensor for the WFS and the interaction matrix. This paper presents preliminary results obtained from experiments after closing the loop using a leaky integrator.

The Multi-conjugate Adaptive Techniques Test Optics (MATTO) is a comprehensive adaptive optics (AO) test bench in development at the INAF-Astronomical Observatory of Padova. Actining as a wide field AO facility, MATTO aims to host future proof-of-concept tests of new methods and serves as a versatile platform for researching and refining Multi-Conjugate Adaptive Optics (MCAO) techniques across diverse conditions. MATTO features independently configurable modules: the reference source module generates atmosphere-perturbed beams, simulating both natural and artificial references with various spectra and asterisms. A telescope simulator module replicates the lower atmosphere's beam geometry by combining light from these references. The MCAO correction module, equipped with three large deformable mirrors, enables the implementation of various compensation schemes with variable conjugation altitudes. Additionally, a sensing module equipped with spatial light modulators (SLM), allows to replicate a range of wavefront sensors, offering flexibility in the positioning of the sensing elements. MATTO emerges as a flexible and essential tool for advancing MCAO research and development.

Low-wind effect is a strong limitation to direct imaging of exoplanets from ground-based telescopes, such as the Subaru telescope, the Very Large Telescope and probably the future extremely large telescopes. To mitigate it, we propose to design coronagraphs passively robust to low-wind effect. The Redundant Apodized Pupils (RAPs) are built so each pupil petal independently contributes to the contrast and therefore petal-level errors do not impact the final coronagraphic image, up to the loss of coherence in the star image. In this paper, we present the first experimental validation of the RAP concept, which is now applied on the Subaru/SCExAO instrument. We have designed three RAPs: two for the infrared channel (CHARIS) and one for the visible instrument (VAMPIRES). After these designs having been set up on the instrument in September 2023, we conducted internal source tests and obtained a contrast robustness up to a few radians. After this first experimental application, the RAP technology will be adapted, at higher contrasts (10⁻⁸-10⁻⁹), to segment-level errors, one of the main limitations for space segmented telescopes like the Habitable Worlds Observatory.

Event-based sensors detect only changes in the brightness across a field of view, with each pixel producing an asynchronous stream of spatial-temporal events data, rather than recording frames of overall illumination of a scene like a traditional frame-based sensor. The location, timestamp, and polarity (positive or negative change) of the recorded events provides low bandwidth data that is useful in real-time sensing of changes in the field of view. These features result in advantages such as high temporal resolution, low latency, high dynamic range, and low power consumption. The use of these sensors has been explored in areas such as object tracking, robotics, and space situational awareness. We are proposing a new application of the event-based sensor in wavefront sensing for adaptive optics. At the Advanced Instrumentation and Technology Centre (AITC) in the Australian National University (ANU), a test bench has been built to test this type of sensor. This study will present the results of this laboratory testing to characterise an event-based sensor’s capabilities to detect tip-tilt aberrations in different conditions, such as background illumination levels. In particular, the event-based sensor’s immunity to a constant background illumination was investigated by introducing an external light source into the scene and recording its performance for different signal strengths. We will present the results of the bench testing, the error budget for tip-tilt sensing using these event-based detectors, and a characterisation of the response of event-based sensors to different illumination conditions.

Most of the current wavefront sensors used in adaptive optics systems estimate the phase of the wavefront indirectly by measuring the local gradients. In strong turbulence the AO correction decreases dramatically, meaning poor wavefront reconstruction. This is due to insufficient wavefront spatial sampling and large signal amplitude variations induced by scintillation, which reduce the accuracy of centroiding algorithms. Direct wavefront measurements, instead of its derivatives, with adequate spatial sampling are ideally suited. Interferometric techniques may be used in alternative to slope-based, or curvature-based wavefront sensors. In this work, a novel design of a point diffraction interferometer (PDI) wavefront sensor is presented which aims to optimise the light throughput and dynamic range while keeping its high sensitivity. This design is an optimised PDI wavefront sensor with a central pinhole. The modelling of this sensor using numerical propagation with Fourier optics is presented. A framework has been established to retrieve the phase reversing the interferometric process, which differs from traditional methods which typically use an off-axis pinhole or phase-stepping. These results look promising showing accurate phase retrieval in a variety of conditions. Ultimately, to overcome the non-linearity of the PDI, machine learning will be used to retrieve the phase and perform prediction. Our preliminary results on the use of machine learning for phase retrieval are also presented.

The Ingot WFS was designed to overcome some of the challenges present in classical wavefront sensors when they deal with sodium LGSs. This innovative sensor works by sensing the full 3D volume of the elongated LGS and is suitable for use in very large telescopes. A test bench has been assembled at the INAF, Osservatorio Astronomico di Padova laboratories to test and characterize the functioning of the Ingot WFS. In this work, we summarize the main results of the tests performed on a new search algorithm. Then, we move towards a more accurate simulation of the sodium LGS by replicating real time-varying sodium layer profiles. The study of their impact on the ingot pupil signals is described in this work.

The new generation of extremely large telescope (ELT) introduces many challenges in optics and engineering. A key challenge is the development of an adaptive optics system able to handle elongated laser guide star (ELGS). Classic wavefront sensor (WFS), such as the shack-hartmann wavefront sensor (SHWFS) or pyramidal wavefront sensor (PyWFS), are not able to readily handle elongated stars, which gets worse when the atmospheric turbulence becomes stronger. In this work, we present a novel complex field wavefront sensor (CFWFS) that can reconstruct the phase and amplitude of the extended bodies at the image plane, and then it is able to recover the turbulent phase at the pupil plane. The proposed WFS scheme uses a four times faster parallel phase retrieval algorithm with only eight designed coded aperture (DCA) that is designed using sphere packing coded apertures (SPCA). We present a collection of encouraging preliminary simulation results.

Adaptive optics (AO) is crucial for extreme Large Telescopes (ELTs), and its core of operation lies in the use of wavefront sensors. Although the Shack Hartmann and Pyramid Wavefront Sensors are more common, the axicon wavefront sensor (AxWFS) is a less-explored alternative, where the light is projected onto the detector over a doughnut-shape area. This study introduces a groundbreaking enhancement, employing a state-of-the-art deep neural network to perform wavefront estimation from the intensity changes within the ring produced by the axicon under different turbulence conditions, without requiring any optical modulation.

Local amplitude aberrations caused by scintillation can impact the reconstruction process of a wavefront sensor (WFS) by inducing a spatially non-uniform intensity at the pupil plane. This effect is especially relevant for the commonly-used Shack-Hartmann WFS (SHWFS), which can lose slope information for portions of the beam where the signal is faint, leading to reduced reconstruction performance and eventually total failure as the level of scintillation increases. An alternative WFS is needed for such conditions. The nonlinear curvature wavefront sensor (nlCWFS) has been shown to achieve better sensitivity compared to the SHWFS under low light levels. Additionally, the nlCWFS has demonstrated the ability to maintain its sensitivity in the presence of scintillation, using amplitude aberrations to help inform the reconstruction process, rather than hinder. Experiments to date have thus far only shown reconstruction results for a single scintillation value. Building upon previous simulations and laboratory experiments, we have built a testbed to quantify the effects of varying scintillation strength on the wavefront reconstruction performance of the nlCWFS compared to an equivalent SHWFS. In this paper, we present results showing the difference in performance between the nlCWFS and SHWFS as a function of relative flux and scintillation strength.

Laser guide star (LGS) wavefront sensing (WFS) is insensitive to tip/tilt, and the variability of the sodium layer altitude in the atmosphere compromises focus measurements. Consequently, sensing of tip/tilt and focus needs to be done separately by means of faint natural guide stars (NGS). In this article, we study and compare three different single-image-phase-diversity (SIPD) algorithms for this specific application, namely Gerchberg-Saxton (GS), Linearized Focal Plane Technique (LiFT), and Fast&Furious (F&F) using high-fidelity Monte Carlo simulations. We present a complete study regarding the performance of GS, LiFT, and F&F under realistic conditions of flux, SNR, and sampling. In addition, we also used these algorithms to measure non-common path aberrations (NCPA), pupil fragmentation modes, and primary mirror phasing errors.

We examine several focal plane wavefront sensing (FPWFS) approaches from a theoretical perspective, specifically comparing their fundamental origins and similarities. We consider various techniques, including the differential optical transfer function wavefront sensor, the self-coherent camera wavefront sensor, the fast-modulated self-coherent camera wavefront sensor, and other variants, as well as pair-wise probing. They are evaluated within a unified framework based on precise optical transfer function analysis and their implementation on the high-contrast imaging SPEED test bed. These concepts are highly similar in essence, even serving as mere extensions of one another. Indeed, we emphasise that these FPWFS can be seen as different expressions or embodiment of the same underlying principles.

Differential optical transfer function (dOTF) is a model-independent image-based wavefront sensor for measuring the complex field. This sensor-less wavefront sensing technique is efficient for precise non-common path aberrations (NCPA) measurement and the phasing of segmented telescopes. In this communication, we report on a thorough exploration of the dOTF method with the SPEED facility for NCPA and cophasing optics application.

The Pyramid Wavefront Sensor (PWFS) is one of the preferred choices for measuring wavefront aberrations for adaptive optics in highly sensitive astronomical applications. Despite its inherent high sensitivity, it has a low linearity that degrades the operational range of the phase estimation. This problem has been solved by optically modulating the PSF across the pyramid. However, modulation requires movable physical parts, requiring additional calibration while degrading the sensitivity in exchange for linearity. We created an End-To-End (E2E) trainable scheme that includes the PWFS model of propagation, an optical diffractive layer at the Fourier plane, and a state-of-the-art deep neural network that performs wavefront reconstruction. The joint training routine for the physical and digital trainable elements is conducted under a variety of atmospheric conditions simulated at different strengths along with its nth-Zernike decomposition for further comparison with the ones estimated by our model. We develop a variety of training schemes, varying turbulence ranges and balance between optical and digital layers. In this way, simulation results show an overall improvement in wavefront estimation even beyond the trained turbulence ranges, improving linearity while trying to maintain the sensitivity at weak turbulence, surpassing previous results that considered only one diffractive element and linear wavefront estimation. We are currently performing experimental closed-loop adaptive optics tests, while simulations are displaying encouraging results.

This work presents the conceptual design of a wavefront sensor utilizing the double-roof pyramid prism proposed for the On-Instrument Wavefront Sensor (OIWFS) within the Giant Magellan Telescope Multi-Object Astronomical and Cosmological Spectrograph (GMACS). It details the design process, presents simulation methods and results to verify the sensor’s performance, and investigates the sensor’s precision and limits by the telescope primary segments tilt to be estimated. The results of the simulations show that the pyramidal sensor has sufficient sensitivity to measure misalignment between the primary segments of up to 3μrad with an error of less than 5% and proved to be effective in estimating the wavefront slope for these limits. The optical model generated images of the exit pupil on the detector in compliance with the precautions demonstrated regarding field rotation, lateral color distortions, differential distortions, and pupil misalignments. The mechanical model resulted in an instrument that allows a complete scan over the external field intended for the search for a guide star and a detailed mechanical design for the manufacture of the pyramidal prisms. Opto-mechanical COTS elements were presented to exemplify the system. This contribution adds to the ongoing development of adaptive optics technology for GMACS on the Giant Magellan Telescope (GMT).