Wavefront outer scale deduced from interferometric dispersed fringes

Maire, Jérôme; Ziad, Aziz; Borgnino, J.; Mourard, D.; Martin, F.; Jankov, S.; Bonneau, Dominique; Patru, Fabien

doi:10.1051/0004-6361:20052806

Cited by 14 publications

(12 citation statements)

References 30 publications

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“…As shown in Fig. 10, the standard deviation of the optical path difference σ OPD (Maire et al 2006) for an interferometer at Dome C has a log-normal distribution with a median value of 1.84 μm for a 1 m telescope diameter and 100 m baseline. For the same interferometer at Paranal the σ OPD is ∼3 μm for median values of seeing and outer scale measured with the GSM .…”

Section: Discussionmentioning

confidence: 97%

“…In interferometry the fringe excursion is strongly dependent on the outer scale according to the telescope diameter and the baseline (Mariotti 1994;Conan et al 2000;Ziad et al 2004;Maire et al 2006). As the measured outer scale at Dome C is smaller than at mid-latitude observatories, it is, then, expected that the fringe excursion should be smaller.…”

Section: Discussionmentioning

confidence: 99%

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First statistics of the turbulence outer scale at Dome C

Ziad¹,

Aristidi²,

Agabi³

et al. 2008

A&A

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Context. The outer scale of wavefronts is of interest for the dimensioning and the optimisation of the High Angular Resolution techniques such as Interferometry and Adaptive Optics, particularly for the new generation of telescopes such as the Extremely Large Telescopes (ELT). Aims. We aim to provide the first statistics of the outer scale at Dome C site in Antarctica to finalize the characterization of this site. Methods. A new version of the Generalized Seeing Monitor has been developed for extremely cold conditions. Two DIMMs (Differential Image Motion Monitor) were coupled to extract Angle-of-Arrival (AA) fluctuations using CCD detectors. Correlations of these AA fluctuations for different baselines lead to outer scale estimations. Results. For the first time, statistics of the outer scale at Dome C are provided leading to small values in the surface layer at Dome C. These small outer scale values compared to temperate sites considerably reduce the fringe excursion of interferometers and the low orders of the normalized amplitude of atmospheric Zernike coefficients, particularly the tip-tilt. Conclusions. The Dome C small outer scale combined with the large coherence time and large isoplanatic angle are very useful for the development of Adaptive Optics systems and long-baseline interferometers.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

First statistics of the turbulence outer scale at Dome C

Ziad¹,

Aristidi²,

Agabi³

et al. 2008

A&A

Self Cite

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show abstract

“…The Generalized Seeing Monitor (GSM) instrument is dedicated to measurements of this outer scale (Martin et al 1994), and several site‐testing campaigns have been carried out worldwide (Ziad et al 2000). Measurements of the outer scale have been confirmed by processing data obtained with existing high angular resolution instruments such as optical interferometers (Ziad et al 2004; Maire et al 2006) and adaptive optics systems (Rigaut et al 1991; Schöck et al 2003; Fusco et al 2004). However, there is limited knowledge about the properties and statistics of a large‐scale wavefront.…”

Section: Introductionmentioning

confidence: 84%

Measurements of profiles of the wavefront outer scale using observations of the limb of the Moon

Maire¹,

Ziad²,

Borgnino³

et al. 2007

Monthly Notices of the Royal Astronomical Society

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The wavefront outer scale is an important parameter to use when evaluating the experimental performance of large aperture telescopes. Knowledge of three‐dimensional atmospheric wavefront distortions is required for specifications of multiconjugate adaptive optics systems, which are essential for observations using Extremely Large Telescopes with a wider field of view. We aim to estimate the vertical distribution of the wavefront outer scale. We analyse the angular correlation of the fluctuations of the wavefront angle of arrival, deduced from image motion of the limb of the Moon. We use a simulated annealing algorithm to deduce the height dependence of the wavefront outer scale with given C2N profiles simultaneously measured with the scintillation detection and ranging (SCIDAR) instrument. We present results obtained during two campaigns of observation at the Mauna Kea Observatory (Hawaii) and the Observatoire de Haute Provence (France). Estimated profiles of the outer scale exhibit smaller values in the boundary layer than in the free atmosphere. Comparisons with measurements of the outer scale using the Generalized Seeing Monitor (GSM) are possible and give good agreement. We consider some implications for adaptive optics systems.

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“…In astronomical applications, the outer scale of the OT was studied for a long time in connection with long‐baseline interferometry (Davis et al ; Avila et al ; Maire et al ). The development of adaptive optics on large telescopes also requires the correct description of the spectrum of phase perturbations in the low‐frequency region (Conan et al ; Tokovinin, Sarazin & Smette ; Martinez et al ).…”

Section: The Impact Of the Outer Scale Of Turbulencementioning

confidence: 99%

Stellar scintillation on large and extremely large telescopes

Kornilov

2012

Monthly Notices of the Royal Astronomical Society

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The accuracy of ground-based astronomical photometry is limited by two factors: photon statistics and stellar scintillation arising when starlight passes through the Earth's atmosphere. This paper examines the theoretical role of the outer scale L O of the optical turbulence (OT), which suppresses the low-frequency component of the scintillation. It is shown that for typical values of L O ∼ 25-50 m, this effect becomes noticeable for telescopes of diameter about 4 m. On extremely large, 30-40 m, telescopes with exposures longer than a few seconds, the inclusion of the outer scale in the calculation reduces the scintillation power by more than a factor of 10 relative to conventional estimates. The details of this phenomenon are discussed for various models of non-Kolmogorov turbulence. In addition, a quantitative description of the influence of the telescope central obscuration on the measured scintillation noise is introduced and combined with the effect of the outer scale. Evaluation of the scintillation noise on future TMT and E-ELT telescopes predicts an amplitude of approximately 10 μmag for a 60-s exposure.

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Wavefront outer scale deduced from interferometric dispersed fringes

Cited by 14 publications

References 30 publications

First statistics of the turbulence outer scale at Dome C

First statistics of the turbulence outer scale at Dome C

Measurements of profiles of the wavefront outer scale using observations of the limb of the Moon

Stellar scintillation on large and extremely large telescopes

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