Temporal characterization of Zernike decomposition of atmospheric turbulence

Snyder, A.; Srinath, Srikar; Macintosh, Bruce

doi:10.1117/12.2234362

Cited by 6 publications

(6 citation statements)

References 4 publications

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“…The Zernike coefficients are created from expanding the Shack-Hartmann slopes into Zernike polynomials. The temporal power spectral density of the Zernike coefficients, as well as the applied DM voltages (commands), were then used to calculate the atmospheric seeing and the pseudo-Strehl numbers (see e.g., Fusco et al, 2004 [37], Snyder et al, 2016 [38]). Figure 5a compares the CIAO calculated seeing with the seeing recorded by the Paranal Astronomical Site Monitor (ASM) at the time of the CIAO observation.…”

Section: Statistical Review Of Three Years Of Ciao Operationmentioning

confidence: 99%

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

et al. 2020

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This article describes the operation of the near-infrared wavefront sensing based AdaptiveOptics (AO) system CIAO. The Coudé Infrared Adaptive Optics (CIAO) system is a central auxiliarycomponent of the Very Large Telescope (VLT) interferometer (VLTI). It enables in particular theobservations of the Galactic Center (GC) using the GRAVITY instrument. GRAVITY is a highlyspecialized beam combiner, a device that coherently combines the light of the four 8-m telescopesand finally records interferometric measurements in the K-band on 6 baselines simultaneously.CIAO compensates for phase disturbances caused by atmospheric turbulence, which all four 8mUnit Telescopes (UT) experience during observation. Each of the four CIAO units generates analmost diffraction-limited image quality at its UT, which ensures that maximum flux of the observedstellar object enters the fibers of the GRAVITY beam combiner. We present CIAO performance dataobtained in the first 3 years of operation as a function of weather conditions. We describe how CIAOis configured and used for observations with GRAVITY. In addition, we focus on the outstandingfeatures 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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Section: Statistical Review Of Three Years Of Ciao Operationmentioning

confidence: 99%

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

et al. 2020

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“…The altitude and Fried parameter r 0 for each layer are taken from median seeing atmospheric measurements at Cerro Pachón. 3 The wind speed for each layer is drawn randomly from a uniform distribution between 0 and the maximum wind speed, which increases with altitude as shown in the table.…”

Section: Simulationsmentioning

confidence: 99%

“…The amount of power at each temporal frequency -called the power spectral density (PSD) -is another way of characterizing turbulence. 3 In particular, we can compare the slopes of the PSDs for data and simulations with the power law slope expected for a Kolmogorov turbulence model. As outlined in Ref 3, we decompose the wavefronts from reconstruction of GPI telemetry and from simulations into Zernike functions, a complete basis set of orthogonal functions describing optical aberrations.…”

Section: Characterizing Turbulence Using Wavefrontsmentioning

confidence: 99%

“…2 By saving the commands sent to these mirrors, one can later reconstruct the phase of the wavefront at the pupil. 3 The reconstructed wavefront telemetry from GPI can provide information about the atmospheric conditions and parameters at Cerro Pachón. In particular, by comparing simulated wavefronts to these data, we can validate certain aspects of atmospheric simulations (e.g., in Galsim).…”

Section: Ao Telemetry From Gpimentioning

confidence: 99%

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Characterization of atmospheric turbulence for the Large Synoptic Survey Telescope

Hébert¹,

Macintosh²,

Burchat³

2018

Ground-Based and Airborne Telescopes VII

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One of the scientific goals of the Large Synoptic Survey Telescope (LSST) is to measure the evolution of dark energy by measuring subtle distortions of galaxy shapes due to weak gravitational lensing caused by the evolving dark matter distribution. Understanding the point spread function (PSF) for LSST is a crucial step to accurate measurements of weak gravitational lensing. Atmospheric contributions dominate the LSST PSF. Simulations of Kolmogorov turbulence models are commonly used to characterize and correct for these atmospheric effects. In order to validate these simulations, we compare the predicted atmospheric behavior to empirical data. The simulations are carried out in GalSim, an open-source software package for simulating images of astronomical objects and PSFs. Atmospheric simulations are run by generating large phase screens at varying altitude and evolving them over long time scales. We compare the turbulence strength and temporal behavior of atmospheres generated from simulations to those from reconstructed telemetry data from the Gemini Planet Imager (GPI). GPI captures a range of spatial frequencies by sampling the atmosphere with 18-cm subapertures. The LSST weak lensing analysis will measure correlations of galaxy ellipticity, requiring very accurate knowledge of the magnitude and correlations of PSF shape parameters. Following from the first analysis, we use simulations and sequential short exposure observations from the Differential Speckle Survey Instrument (DSSI) to study the behavior of PSF parameters -e.g., ellipticity and size -as a function of exposure time. These studies could help inform discussions of possible variable exposure times for LSST visits for example, to provide more uniform depth of visits.

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“…Together with the temporal power spectral density of the Zernike coefficients and the DM commands, the atmospheric seeing, atmospheric AO coherence time, and pseudo-Strehl numbers were determined (see e.g Fusco et al 2004,36. Snyder et al 201637 ).CIAO performance over 3 years (2017-2019) Galactic center observations with GRAVITY 0estimated Seeing / arcsec (a) CIAO estimated seeing vs recorded Paranal Astronomical Site Monitor (ASM) seeing. CIAO performance over 3 years (2017-2019) Galactic center observations with GRAVITY 0CIAO estimated K-band Strehl number vs CIAO estimated seeing.…”

mentioning

confidence: 99%

Infrared wavefront sensing for adaptive optics assisted Galactic Center observations with the VLT interferometer and GRAVITY: operation and results

Hippler¹,

Brandner²,

Scheithauer³

et al. 2020

Preprint

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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, calibrated, and finally 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.

show abstract

Temporal characterization of Zernike decomposition of atmospheric turbulence

Cited by 6 publications

References 4 publications

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

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

Characterization of atmospheric turbulence for the Large Synoptic Survey Telescope

Infrared wavefront sensing for adaptive optics assisted Galactic Center observations with the VLT interferometer and GRAVITY: operation and results

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