Wave-front temporal spectra in high-resolution imaging through turbulence

Conan, Jean-Marc; Rousset, G.; Madec, Pierre-Yves

doi:10.1364/josaa.12.001559

Cited by 236 publications

(183 citation statements)

References 25 publications

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“…For stars oriented exactly along the wind, the PSD increases proportionally to f 2−p , which is in agreement with theoretical results by Martin (1987) and Conan et al (1995) drawn at p = 2/3. At orthogonal position of stars, the PSD is slowly decreasing with f , and up to f 1.0b −1 is approximately a white noise spectrum.…”

Section: A Model Of the Temporal Power Spectrum Of Differential Imagesupporting

confidence: 91%

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Non-Kolmogorov features of differential image motion restored from the Multichannel Astrometric Photometer data

Lazorenko

2002

A&A

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Abstract. In this paper we present a new restoration of atmospheric turbulent parameters using published data on image motion observations with the Multichannel Astrometric Photometer. These data have been previously analyzed by Han (1989) whose estimate of the power of the phase structure function α = 1.64 was close to the 5/3 value expected for the Kolmogorov atmospheric turbulence. Investigating the temporal image motion spectrum, we show, however, that the experimental data do not follow predictions of the Kolmogorov model. The best fitting of the observed spectrum is achieved with α = 1.9−2.0, which is typical of non-classic phase distortions. The outer scale of turbulence was found to be 1800 m or longer. Expressions for the non-Kolmogorov temporal spectrum of differential image motion allowing for a finite outer scale length are given.

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Section: A Model Of the Temporal Power Spectrum Of Differential Imagesupporting

confidence: 91%

“…Transformation of spatial PSD F(u, v) into temporal spectrum g( f ) is performed (Martin 1987;Conan et al 1995) by integration of F(u, v) over spatial frequency v (across a wind), with a subsequent application of the Taylor transformation u = f /V:…”

Section: A Model Of the Temporal Power Spectrum Of Differential Imagementioning

confidence: 99%

Non-Kolmogorov features of differential image motion restored from the Multichannel Astrometric Photometer data

Lazorenko

2002

A&A

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“…Considering the turbulence contribution, Conan et al (1995) derive the asymptotic laws for single turbulence-layer OPD spectra…”

Section: Disturbance Simulationmentioning

confidence: 99%

Kalman-filter control schemes for fringe tracking

Perrin

Choquet

et al. 2012

A&A

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Context. The implementation of fringe tracking for optical interferometers is inevitable when optimal exploitation of the instrumental capacities is desired. Fringe tracking allows continuous fringe observation, considerably increasing the sensitivity of the interferometric system. In addition to the correction of atmospheric path-length differences, a decent control algorithm should correct for disturbances introduced by instrumental vibrations, and deal with other errors propagating in the optical trains. Aims. In an effort to improve upon existing fringe-tracking control, especially with respect to vibrations, we attempt to construct control schemes based on Kalman filters. Kalman filtering is an optimal data processing algorithm for tracking and correcting a system on which observations are performed. As a direct application, control schemes are designed for GRAVITY, a future four-telescope near-infrared beam combiner for the Very Large Telescope Interferometer (VLTI). Methods. We base our study on recent work in adaptive-optics control. The technique is to describe perturbations of fringe phases in terms of an a priori model. The model allows us to optimize the tracking of fringes, in that it is adapted to the prevailing perturbations. Since the model is of a parametric nature, a parameter identification needs to be included. Different possibilities exist to generalize to the four-telescope fringe tracking that is useful for GRAVITY. Results. On the basis of a two-telescope Kalman-filtering control algorithm, a set of two properly working control algorithms for four-telescope fringe tracking is constructed. The control schemes are designed to take into account flux problems and low-signal baselines. First simulations of the fringe-tracking process indicate that the defined schemes meet the requirements for GRAVITY and allow us to distinguish in performance. In a future paper, we will compare the performances of classical fringe tracking to our Kalman-filter control. Conclusions. Kalman-filter based control schemes will likely become the next standard for fringe tracking, providing the possibility to maximize the tracking performance. The results of the present study are currently being incorporated into the final design of GRAVITY.

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“…In optical interferometry, the piston effect between the two arms of an interferometer induces an erratic movement of the fringes. The power spectrum for the fringe motion follows the classical Kolmogorov spectrum for atmospheric turbulence (Conan et al 1995), with a typical standard deviation of 20 µm rms. In the case of GENIE, this would completely ruin the nulling process because the rms fringe excursion is larger than the fringe spacing itself: the optical axis would therefore see both dark and bright fringes as atmospheric turbulence changes the phase difference between the apertures.…”

Section: Effects Of Phase Errorsmentioning

confidence: 92%

Effects of atmospheric turbulence on the GENIE nulling interferometer

Absil

2004

EAS Publications Series

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Abstract. Two competitive design studies for the Ground-based European Nulling Interferometer Experiment (GENIE) have recently been initiated by the European Space Agency and the European Southern Observatory. A major issue in these studies is the influence of atmospheric turbulence on the performance of the instrument, and how atmospheric effects can be compensated in order to reach the goal performance (detection of faint exozodiacal clouds). In this paper, we review the main atmospheric processes affecting a nulling interferometer and discuss possible ways to reduce them by means of real-time control systems. Preliminary performance estimates of GENIE are then presented. The effects of the thermal background and its fluctuations are not considered here.

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Wave-front temporal spectra in high-resolution imaging through turbulence

Cited by 236 publications

References 25 publications

Non-Kolmogorov features of differential image motion restored from the Multichannel Astrometric Photometer data

Non-Kolmogorov features of differential image motion restored from the Multichannel Astrometric Photometer data

Kalman-filter control schemes for fringe tracking

Effects of atmospheric turbulence on the GENIE nulling interferometer

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