NAOS, the first AO system of the VLT: on-sky performance

Rousset, G.; Lacombe, F.; Puget, P.; Hubin, N.; Gendron, É.; Fusco, Thierry; Arsenault, Robin; Charton, J.; Feautrier, Philippe; Gigan, P.; Kern, P.; Lagrange, Anne-Marie; Madec, Pierre-Yves; Mouillet, D.; Rabaud, Didier; Rabou, Patrick; Stadler, Eric; Zins, G.

doi:10.1117/12.459332

Cited by 301 publications

(90 citation statements)

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“…The observations were carried out in April 2002 during the commissioning of the NACO/VLT system (Lenzen et al 1998;Rousset et al 2003;Hartung et al 2000) in the Ks band. In order to simultaneously measure two orthogonal components of the polarized light, a Wollaston prism was introduced in the light path.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

NACO polarimetric differential imaging of TW Hya

Apai

Pascucci

Brandner

et al. 2004

A&A

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Abstract. We present high-contrast imaging data on the disk of the classical T Tauri star TW Hya. The images were obtained through the polarimetric differential imaging technique with the adaptive optics system NACO. Our commissioning data show the presence of polarized disk emission between 0.1 and 1.4 from the star. We derive the first Ks-band radial polarized intensity distribution. We show that the polarized intensity compares well to shorter wavelengths surface brightness observations and confirm the previously reported gradual slope change around 0.8 . These results show the potential of the new polarimetric differential imaging technique at 8 m-class telescopes to map the inner regions of protoplanetary disks.

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Section: Observations and Data Reductionmentioning

confidence: 99%

NACO polarimetric differential imaging of TW Hya

Apai

Pascucci

Brandner

et al. 2004

A&A

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“…7 This type of approach has been successfully applied on NAOS-CONICA 8 or Keck 9 and has led to a significant gain of global system performance. 10 Even if a real improvement can be seen on pre-compensated images, a significant amount of aberrations are still not corrected.…”

Section: Introductionmentioning

confidence: 99%

Calibration and precompensation of noncommon path aberrations for extreme adaptive optics

et al. 2007

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Non-Common Path Aberrations (NCPA) are one of the main limitations for extreme Adaptive Optics (AO) system. NCPA prevent extreme AO systems to achieve their ultimate performance. These static aberrations are unseen by the wave front sensor and therefore not corrected in closed loop. We present experimental results validating new procedures of measurement and pre-compensation of the NCPA on the AO bench at ONERA. The measurement procedure is based on new refined algorithms of phase diversity. The pre-compensation procedure makes use of a pseudo-closed loop scheme to overcome the AO wavefront sensor model uncertainties. Strehl Ratio obtained in the images reaches 98.7 % @ 632.8 nm. This result allows us to be confident of achieving the challenging performance required for extrasolar planet direct observation.

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“…Thus, the number of DM actuators, the number of sub-apertures on the WFS and on DAM are all equal. We consider the AO sampling of N × N = 15 × 15 and N × N = 40 × 40 , corresponding respectively to a sub-aperture diameter d = 50 cm and d = 20 cm over a telescope diameter D = 8 m. These cases mimic the AO sampling of NAOS 22 and SPHERE 23 at the VLT.…”

Section: Dam Wavefront (Amplitude and Phase)mentioning

confidence: 99%

Discretized aperture mapping with a micro-lenses array for interferometric direct imaging

Patru

Antichi

Mawet³

et al. 2014

SPIE Proceedings

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Discretized Aperture Mapping (DAM) appears as an original filtering technique easy to play with existing adaptive optics (AO) systems. In its essential DAM operates as an optical passive filter removing part of the phase residuals in the wavefront without introducing any difficult-to-align component in the Fourier conjugate of the entrance pupil plane. DAM reveals as a new interferometric technique combined with spatial filtering allowing direct imaging over a narrow field of view (FOV). In fact, the entrance pupil of a single telescope is divided into many sub-pupils so that the residual phase in each sub-pupil is filtered up to the DAM cut-off frequency. DAM enables to smooth the small scale wavefront defects which correspond to high spatial frequencies in the pupil plane and to low angular frequencies in the image plane. Close to the AO Nyquist frequency, such pupil plane spatial frequencies are not well measured by the wavefront sensor (WFS) due to aliasing. Once bigger than the AO Nyquist frequency, they are no more measured by the WFS due to the fitting limit responsible for the narrow AO FOV. The corresponding image plane angular frequencies are not transmitted by DAM and are useless to image small FOVs, as stated by interferometry. That is why AO and DAM are complementary assuming that the DAM cut-off frequency is equal to the AO Nyquist frequency. Here we describe the imaging capabilities when DAM is placed downstream an AO system, over a convenient pupil which precedes the scientific detector. We show firstly that the imaging properties are preserved on a narrow FOV allowing direct imaging throughout interferometry. Then we show how the residual pupil plane spatial frequencies bigger than the AO Nyquist one are filtered out, as well as the residual halo in the image is dimmed.

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NAOS, the first AO system of the VLT: on-sky performance

Cited by 301 publications

References 0 publications

NACO polarimetric differential imaging of TW Hya

NACO polarimetric differential imaging of TW Hya

Calibration and precompensation of noncommon path aberrations for extreme adaptive optics

Discretized aperture mapping with a micro-lenses array for interferometric direct imaging

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