scholarly journals Performance limits of adaptive-optics/high-contrast imagers with pyramid wavefront sensors

2020 ◽  
Vol 495 (4) ◽  
pp. 4380-4391
Author(s):  
Carlos M Correia ◽  
Olivier Fauvarque ◽  
Charlotte Z Bond ◽  
Vincent Chambouleyron ◽  
Jean-François Sauvage ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Large Scale ◽  
Near Infrared ◽  
Dynamic Control ◽  
Diffraction Theory ◽  
Peak Performance ◽  
High Contrast ◽  
Reconstruction Algorithms ◽  
Performance Limits ◽  
Wavefront Sensors

ABSTRACT Advanced adaptive-optics (AO) systems will likely utilize pyramid wavefront sensors (PWFSs) over the traditional Shack–Hartmann sensor in the quest for increased sensitivity, peak performance and ultimate contrast. Here, we explain and quantify the PWFS theoretical limits as a means to highlight its properties and applications. We explore forward models for the PWFS in the spatial-frequency domain: these prove useful because (i) they emanate directly from physical-optics (Fourier) diffraction theory; (ii) they provide a straightforward path to meaningful error breakdowns; (iii) they allow for reconstruction algorithms with $O (n\, \log(n))$ complexity for large-scale systems; and (iv) they tie in seamlessly with decoupled (distributed) optimal predictive dynamic control for performance and contrast optimization. All these aspects are dealt with here. We focus on recent analytical PWFS developments and demonstrate the performance using both analytic and end-to-end simulations. We anchor our estimates on observed on-sky contrast on existing systems, and then show very good agreement between analytical and Monte Carlo performance estimates on AO systems featuring the PWFS. For a potential upgrade of existing high-contrast imagers on 10-m-class telescopes with visible or near-infrared PWFSs, we show, under median conditions at Paranal, a contrast improvement (limited by chromatic and scintillation effects) of 2×–5× when just replacing the wavefront sensor at large separations close to the AO control radius where aliasing dominates, and of factors in excess of 10× by coupling distributed control with the PWFS over most of the AO control region, from small separations starting with an inner working angle of typically 1–2 λ/D to the AO correction edge (here 20 λ/D).

scholarly journals Multiconjugate Adaptive Optics for Astronomy

2018 ◽  
Vol 56 (1) ◽  
pp. 277-314 ◽  
Author(s):  
François Rigaut ◽  
Benoit Neichel
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Phase Reconstruction ◽  
Large Telescope ◽  
Wavefront Sensors ◽  
Error Sources ◽  
New Concepts ◽  
Year 2000 ◽  
Current Systems ◽  
Solar Astronomy

Since the year 2000, adaptive optics (AO) has seen the emergence of a variety of new concepts addressing particular science needs; multiconjugate adaptive optics (MCAO) is one of them. By correcting the atmospheric turbulence in 3D using several wavefront sensors and a tomographic phase reconstruction approach, MCAO aims to provide uniform diffraction limited images in the near-infrared over fields of view larger than 1 arcmin2, i.e., 10 to 20 times larger in area than classical single conjugated AO. In this review, we give a brief reminder of the AO principles and limitations, and then focus on aspects particular to MCAO, such as tomography and specific MCAO error sources. We present examples and results from past or current systems: MAD (Multiconjugate Adaptive Optics Demonstrator) and GeMS (Gemini MCAO System) for nighttime astronomy and the AO system, at Big Bear for solar astronomy. We examine MCAO performance (Strehl ratio up to 40% in H band and full width at half maximum down to 52 mas in the case of MCAO), with a particular focus on photometric and astrometric accuracy, and conclude with considerations on the future of MCAO in the Extremely Large Telescope and post–HST era.

scholarly journals A triple star in disarray

2020 ◽  
Vol 644 ◽  
pp. A114
Author(s):  
M. Kasper ◽  
K. K. R. Santhakumari ◽  
T. M. Herbst ◽  
R. van Boekel ◽  
F. Menard ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
State Of The Art ◽  
High Contrast ◽  
Compelling Evidence ◽  
T Tauri ◽  
Reflected Light ◽  
First Time ◽  
Triple Star ◽  
Outflow System

Aims. T Tauri remains an enigmatic triple star for which neither the evolutionary state of the stars themselves, nor the geometry of the complex outflow system is completely understood. Eight-meter class telescopes equipped with state-of-the-art adaptive optics provide the spatial resolution necessary to trace tangential motion of features over a timescale of a few years, and they help to associate them with the different outflows. Methods. We used J-, H-, and K-band high-contrast coronagraphic imaging with VLT-SPHERE recorded between 2016 and 2018 to map reflection nebulosities and obtain high precision near-infrared (NIR) photometry of the triple star. We also present H2 emission maps of the ν = 1-0 S(1) line at 2.122 μm obtained with LBT-LUCI during its commissioning period at the end of 2016. Results. The data reveal a number of new features in the system, some of which are seen in reflected light and some are seen in H2 emission; furthermore, they can all be associated with the main outflows. The tangential motion of the features provides compelling evidence that T Tauri Sb drives the southeast–northwest outflow. T Tauri Sb has recently faded probably because of increased extinction as it passes through the southern circumbinary disk. While Sb is approaching periastron, T Tauri Sa instead has brightened and is detected in all our J-band imagery for the first time.

scholarly journals GRAVITY: microarcsecond astrometry and deep interferometric imaging with the VLTI

2007 ◽  
Vol 3 (S248) ◽  
pp. 100-101 ◽  
Author(s):  
F. Eisenhauer ◽  
G. Perrin ◽  
C. Straubmeier ◽  
W. Brandner ◽  
A. Boehm ◽  
...  
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Adaptive Optics ◽  
Near Infrared ◽  
Galactic Center ◽  
Interferometric Imaging ◽  
Wavefront Sensors ◽  
Narrow Angle ◽  
Interferometric Phase ◽  
Wide Range

AbstractWe present the adaptive optics assisted, near-infrared VLTI instrument GRAVITY for precision narrow-angle astrometry and interferometric phase referenced imaging of faint objects. With its two fibers per telescope beam, its internal wavefront sensors and fringe tracker, and a novel metrology concept, GRAVITY will not only push the sensitivity far beyond what is offered today, but will also advance the astrometric accuracy for UTs to 10 μas. GRAVITY is designed to work with four telescopes, thus providing phase referenced imaging and astrometry for 6 baselines simultaneously. Its unique capabilities and sensitivity will open a new window for the observation of a wide range of objects, and — amongst others — will allow the study of motion within a few times the event horizon size of the Galactic Center black hole.

scholarly journals Origin of the asymmetry of the wind driven halo observed in high-contrast images

2018 ◽  
Vol 620 ◽  
pp. L10 ◽  
Author(s):  
F. Cantalloube ◽  
E. H. Por ◽  
K. Dohlen ◽  
J.-F. Sauvage ◽  
A. Vigan ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Predictive Control ◽  
Near Infrared ◽  
Control Algorithms ◽  
Circumstellar Disk ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
The Asymmetry ◽  
Processing Techniques

The latest generation of high-contrast instruments dedicated to exoplanets and circumstellar disk imaging are equipped with extreme adaptive optics and coronagraphs to reach contrasts of up to 10−4 at a few tenths of arcseconds in the near-infrared. The resulting image shows faint features, only revealed with this combination, such as the wind driven halo. The wind driven halo is due to the lag between the adaptive optics correction and the turbulence speed over the telescope pupil. However, we observe an asymmetry of this wind driven halo that was not expected when the instrument was designed. In this letter, we describe and demonstrate the physical origin of this asymmetry and support our explanation by simulating the asymmetry with an end-to-end approach. From this work, we find that the observed asymmetry is explained by the interference between the AO-lag error and scintillation effects, mainly originating from the fast jet stream layer located at about 12 km in altitude. Now identified and interpreted, this effect can be taken into account for further design of high-contrast imaging simulators, next generation or upgrade of high-contrast instruments, predictive control algorithms for adaptive optics, or image post-processing techniques.

scholarly journals Fully Convolutional Approaches for Numerical Approximation of Turbulent Phases in Solar Adaptive Optics

Mathematics ◽  
2021 ◽  
Vol 9 (14) ◽  
pp. 1630
Author(s):  
Francisco García Riesgo ◽  
Sergio Luis Suárez Gómez ◽  
Enrique Díez Alonso ◽  
Carlos González-Gutiérrez ◽  
Jesús Daniel Santos
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
High Altitude ◽  
Adaptive Optics ◽  
Numerical Approximation ◽  
Reconstruction Algorithms ◽  
Wavefront Sensors ◽  
Night Time ◽  
Phase Recovery ◽  
Fully Convolutional Neural Networks

Information on the correlations from solar Shack–Hartmann wavefront sensors is usually used for reconstruction algorithms. However, modern applications of artificial neural networks as adaptive optics reconstruction algorithms allow the use of the full image as an input to the system intended for estimating a correction, avoiding approximations and a loss of information, and obtaining numerical values of those correlations. Although studied for night-time adaptive optics, the solar scenario implies more complexity due to the resolution of the solar images potentially taken. Fully convolutional neural networks were the technique chosen in this research to address this problem. In this work, wavefront phase recovery for adaptive optics correction is addressed, comparing networks that use images from the sensor or images from the correlations as inputs. As a result, this research shows improvements in performance for phase recovery with the image-to-phase approach. For recovering the turbulence of high-altitude layers, up to 93% similarity is reached.

scholarly journals The NIR arm of SHARK: System for coronagraphy with High-order Adaptive optics from R to K bands

2014 ◽  
Vol 14 (3) ◽  
pp. 365-373 ◽  
Author(s):  
Jacopo Farinato ◽  
Carlo Baffa ◽  
Andrea Baruffolo ◽  
Maria Bergomi ◽  
Luca Carbonaro ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
High Order ◽  
High Contrast ◽  
Technical Feasibility ◽  
Conceptual Study

AbstractSHARK is a proposal aimed at investigating the technical feasibility and the scientific capabilities of high-contrast cameras to be implemented at the Large Binocular Telescope (LBT). SHARK foresees two separated channels: near-infrared (NIR) channel and visible, both providing imaging and coronagraphic modes. We describe here the SHARK instrument concept, with particular emphasis on the NIR channel at the level of a conceptual study, performed in the framework of the call for proposals for new LBT instruments. The search for giant extra-Solar planets is the main science case, as we will outline in the paper.

scholarly journals Adaptive Optics Imaging of Circumstellar Environments

2004 ◽  
Vol 221 ◽  
pp. 307-312
Author(s):  
Dániel Apai ◽  
Ilaria Pascucci ◽  
Hongchi Wang ◽  
Wolfgang Brandner ◽  
Thomas Henning ◽  
...  
Keyword(s):  
High Resolution ◽  
Adaptive Optics ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Circumstellar Disks ◽  
Circumstellar Envelope ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Circumstellar Environments

We present results from our high-resolution, high-contrast imaging campaign targeting the circumstellar environments of young, nearby stars of different masses. The observations have been conducted using the ALFA/CA 3.5m and NACO UT4/VLT adaptive optics systems. In order to enhance the contrast we applied the methods PSF-subtraction and polarimetric differential imaging (PDI). The observations of young stars yielded the identification of numerous new companion candidates, the most interesting one being ∼ 0.5″ from FU Ori. We also obtained high-resolution near-infrared imaging of the circumstellar envelope of SU Aur and AB Aur. Our PDI of the TW Hya circumstellar disk traced back the disk emission as close as 0.1″ ≃ 6 AU from the star, the closest yet. Our results demonstrate the potential of the adaptive optics systems in achieving high-resolution and high-contrast imaging and thus in the study of circumstellar disks, envelopes and companions.

scholarly journals Obscuring and Feeding Supermassive Black Holes with Evolving Nuclear Star Clusters

2009 ◽  
Vol 5 (S267) ◽  
pp. 307-312
Author(s):  
M. Schartmann ◽  
A. Burkert ◽  
M. Krause ◽  
M. Camenzind ◽  
K. Meisenheimer ◽  
...  
Keyword(s):  
High Resolution ◽  
Adaptive Optics ◽  
Large Scale ◽  
Near Infrared ◽  
Star Clusters ◽  
Seyfert Galaxies ◽  
Disk Model ◽  
Ngc 1068 ◽  
Hydrodynamical Simulations ◽  
Integral Field Spectrograph

AbstractRecently, high-resolution observations made with the help of the near-infrared adaptive optics integral field spectrograph SINFONI at the VLT proved the existence of massive and young nuclear star clusters in the centers of a sample of Seyfert galaxies. With the help of high-resolution hydrodynamical simulations with the pluto code, we follow the evolution of such clusters, especially focusing on mass and energy feedback from young stars. This leads to a filamentary inflow of gas on large scales (tens of parsecs), whereas a turbulent and very dense disk builds up on the parsec scale. Here we concentrate on the long-term evolution of the nuclear disk in NGC 1068 with the help of an effective viscous disk model, using the mass input from the large-scale simulations and accounting for star formation in the disk. This two-stage modeling enables us to connect the tens-of-parsecs scale region (observable with SINFONI) with the parsec-scale environment (MIDI observations). At the current age of the nuclear star cluster, our simulations predict disk sizes of the order 0.8 to 0.9 pc, gas masses of order 106M⊙, and mass transfer rates through the inner boundary of order 0.025 M⊙yr−1, in good agreement with values derived from observations.

scholarly journals SPHERE: the exoplanet imager for the Very Large Telescope

2019 ◽  
Vol 631 ◽  
pp. A155 ◽  
Author(s):  
J.-L. Beuzit ◽  
A. Vigan ◽  
D. Mouillet ◽  
K. Dohlen ◽  
R. Gratton ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
System Analysis ◽  
Scattered Light ◽  
Dual Band ◽  
High Contrast ◽  
Large Telescope ◽  
Single Observation ◽  
Very Large Telescope ◽  
Circumstellar Environments

Observations of circumstellar environments that look for the direct signal of exoplanets and the scattered light from disks have significant instrumental implications. In the past 15 years, major developments in adaptive optics, coronagraphy, optical manufacturing, wavefront sensing, and data processing, together with a consistent global system analysis have brought about a new generation of high-contrast imagers and spectrographs on large ground-based telescopes with much better performance. One of the most productive imagers is the Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE), which was designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE includes an extreme adaptive optics system, a highly stable common path interface, several types of coronagraphs, and three science instruments. Two of them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager and Spectrograph (IRDIS), were designed to efficiently cover the near-infrared range in a single observation for an efficient search of young planets. The third instrument, ZIMPOL, was designed for visible polarimetric observation to look for the reflected light of exoplanets and the light scattered by debris disks. These three scientific instruments enable the study of circumstellar environments at unprecedented angular resolution, both in the visible and the near-infrared. In this work, we thoroughly present SPHERE and its on-sky performance after four years of operations at the VLT.

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