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 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 Supernovae and cosmology with future European facilities

2013 ◽  
Vol 371 (1992) ◽  
pp. 20120282 ◽  
Author(s):  
I. M. Hook
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
General Purpose ◽  
Type Ia Supernovae ◽  
Large Telescope ◽  
Infrared Telescope ◽  
Type Ia ◽  
Infrared Wavelengths ◽  
Ia Supernovae ◽  
Multi Band

Prospects for future supernova surveys are discussed, focusing on the European Space Agency’s Euclid mission and the European Extremely Large Telescope (E-ELT), both expected to be in operation around the turn of the decade. Euclid is a 1.2 m space survey telescope that will operate at visible and near-infrared wavelengths, and has the potential to find and obtain multi-band lightcurves for thousands of distant supernovae. The E-ELT is a planned, general-purpose ground-based, 40-m-class optical–infrared telescope with adaptive optics built in, which will be capable of obtaining spectra of type Ia supernovae to redshifts of at least four. The contribution to supernova cosmology with these facilities will be discussed in the context of other future supernova programmes such as those proposed for DES, JWST, LSST and WFIRST.

scholarly journals Detection and characterization of two VLM binaries: LP 1033-31 and LP 877-72

2020 ◽  
Vol 498 (1) ◽  
pp. 737-749
Author(s):  
Subhajeet Karmakar ◽  
A S Rajpurohit ◽  
F Allard ◽  
D Homeier
Keyword(s):  
Adaptive Optics ◽  
Spectral Type ◽  
Near Infrared ◽  
Binding Energies ◽  
Secondary Component ◽  
Large Telescope ◽  
Very Large Telescope ◽  
Adaptive Optics Imaging ◽  
M Dwarf

ABSTRACT Using the high-resolution near-infrared adaptive optics imaging from the NaCo instrument at the Very Large Telescope, we report the discovery of a new binary companion to the M-dwarf LP 1033-31 and also confirm the binarity of LP 877-72. We have characterized both the stellar systems and estimated the properties of their individual components. We have found that LP 1033-31 AB with the spectral type of M4.5+M4.5 has a projected separation of 6.7 ± 1.3 AU. Whereas with the spectral type of M1+M4, the projected separation of LP 877-72 AB is estimated to be 45.8 ± 0.3 AU. The binary companions of LP 1033-31 AB are found to have similar masses, radii, effective temperatures, and log g with the estimated values of 0.20 ± 0.04 $\rm {M}_{\odot }$, 0.22 ± 0.03 $\rm {R}_{\odot }$, and 3200 K, 5.06 ± 0.04. However, the primary of LP 877-72 AB is found to be twice as massive as the secondary with the derived mass of 0.520 ± 0.006 $\rm {M}_{\odot }$. The radius and log g for the primary of LP 877-72 AB are found to be 1.8 and 0.95 times that of the secondary component with the estimated values of 0.492 ± 0.011 $\rm {R}_{\odot }$ and 4.768 ± 0.005, respectively. With an effective temperature of 3750 ± 15 K, the primary of LP 877-72 AB is also estimated to be ∼400 K hotter than the secondary component. We have also estimated the orbital period of LP 1033-31 and LP 877-72 to be ∼28 and ∼349 yr, respectively. The binding energies for both systems are found to be >1043 erg, which signifies that both systems are stable.

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 The VLT Interferometer

1994 ◽  
Vol 158 ◽  
pp. 143-150
Author(s):  
T. R. Bedding ◽  
J. M. Beckers ◽  
M. Faucherre ◽  
N. Hubin ◽  
B. Koehler ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
High Sensitivity ◽  
Large Telescope ◽  
Wavefront Correction ◽  
Wavefront Aberrations ◽  
Very Large Telescope ◽  
Infrared Wavelengths ◽  
Very High

One of the observing modes available with the ESO Very Large Telescope will be coherent combination of the light received by up to four 8 m unit telescopes and several 1.8 m auxiliary telescopes. The location of the main telescopes is fixed, while auxiliary telescopes can be moved among some 30 observing stations. The locations of these stations were chosen to augment the (u, v) coverage of the unit telescopes as well as to function as an independent interferometric array.The 8 m telescopes will be equipped with adaptive optics to correct for seeing-induced wavefront aberrations. This wavefront correction will be complete at near-infrared wavelengths, giving the interferometer very high sensitivity in this spectral regime. This paper gives a brief description of the VLT Interferometer and an update on its status.

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.

scholarly journals Science with EPICS, the E-ELT planet finder

2010 ◽  
Vol 6 (S276) ◽  
pp. 343-348
Author(s):  
Raffaele Gratton ◽  
Markus Kasper ◽  
Christophe Vérinaud ◽  
Mariangela Bonavita ◽  
Hans M. Schmid
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Large Telescope ◽  
High Performing ◽  
System A ◽  
Reflected Light ◽  
Integral Field Spectrograph ◽  
Adaptive Optics System ◽  
Integral Field

AbstractEPICS is the proposed planet finder for the European Extremely Large Telescope. EPICS is a high contrast imager based on a high performing extreme adaptive optics system, a diffraction suppression module, and two scientific instruments: an Integral Field Spectrograph (IFS) for the near infrared (0.95-1.65 μm), and a differential polarization imager (E-POL). Both these instruments should allow imaging and characterization of planets shining in reflected light, possibly down to Earth-size. A few high interesting science cases are presented.

scholarly journals Infrared Wavefront Sensing for Adaptive Optics Assisted Galactic Center Observations with the VLT Interferometer and GRAVITY: Operation and Results

Instruments ◽  
2020 ◽  
Vol 4 (3) ◽  
pp. 20
Author(s):  
Stefan Hippler ◽  
Wolfgang Brandner ◽  
Silvia Scheithauer ◽  
Martin Kulas ◽  
Johana Panduro ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Galactic Center ◽  
Weather Conditions ◽  
Wavefront Sensing ◽  
Large Telescope ◽  
Auxiliary Component ◽  
Very Large Telescope ◽  
Beam Combiner ◽  
First Time

This article describes the operation of the near-infrared wavefront sensing based Adaptive Optics (AO) system CIAO. The Coudé Infrared Adaptive Optics (CIAO) system is a central auxiliary component of the Very Large Telescope (VLT) interferometer (VLTI). It enables in particular the observations of the Galactic Center (GC) using the GRAVITY instrument. GRAVITY is a highly specialized beam combiner, a device that coherently combines the light of the four 8-m telescopes and finally records interferometric measurements in the K-band on 6 baselines simultaneously. CIAO compensates for phase disturbances caused by atmospheric turbulence, which all four 8 m Unit Telescopes (UT) experience during observation. Each of the four CIAO units generates an almost diffraction-limited image quality at its UT, which ensures that maximum flux of the observed stellar object enters the fibers of the GRAVITY beam combiner. We present CIAO performance data obtained in the first 3 years of operation as a function of weather conditions. We describe how CIAO is configured and used for observations with GRAVITY. In addition, we focus on the outstanding features of the near-infrared sensitive Saphira detector, which is used for the first time on Paranal, and show how it works as a wavefront sensor detector.

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