Tilt anisoplanatism in laser-guide-star-based multiconjugate adaptive optics

Flicker, Ralf; Rigaut, François; Ellerbroek, Brent L.

doi:10.1051/0004-6361:20030022

Cited by 16 publications

(6 citation statements)

References 17 publications

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“…Throughout the following analysis, we consider the contribution of all the modes to the turbulence-induced wavefront distortions and a reconstruction of tip-tilt at the ground and focus-astigmatisms at the high layer, based on the tip-tilt measurements from three NGSs in equilateral asterism. Such NGS loop can be used for the control of the null modes (Flicker et al 2003) in MCAO systems using a split tomography approach (Gilles & Ellerbroek 2008). The compensation for focus-astigmatisms at the pupil plane is not included in our configuration and this would provide an out of focus and astigmatic PSF; however, this is not a limitation for our analysis as we are interested in investigating the variations of tip-tilt in the field of view.…”

Section: Tip-tilt Anisoplanatism In Mcao-assisted Astrometric Observa...mentioning

confidence: 99%

Temporal spectrum of multiconjugate adaptive optics residuals and impact of tip-tilt anisoplanatism on astrometric observations

Carlà

Plantet

Busoni

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Multi-conjugate adaptive optics (MCAO) will assist a new era of ground-based astronomical observations with the extremely large telescopes and the Very Large Telescope. High precision relative astrometry is among the main science drivers of these systems and challenging requirements have been set for the astrometric measurements. A clear understanding of the astrometric error budget is needed and the impact of the MCAO correction has to be taken into account. In this context, we propose an analytical formulation to estimate the residual phase produced by an MCAO correction in any direction of the scientific field of view. The residual phase, computed in the temporal frequency domain, allows to consider the temporal filtering of the turbulent phase from the MCAO loop and to extract the temporal spectrum of the residuals, as well as to include other temporal effects such as the scientific integration time. The formulation is kept general and allows to consider specific frameworks by setting the telescope diameter, the turbulence profile, the guide stars constellation, the deformable mirrors configuration, the modes sensed and corrected and the tomographic reconstruction algorithm. The formalism is presented for both a closed loop and a pseudo-open loop control. We use our results to investigate the effect of tip-tilt residuals on MCAO-assisted astrometric observations. We derive an expression for the differential tilt jitter power spectrum that also includes the dependence on the scientific exposure time. Finally, we investigate the contribution of the differential tilt jitter error on the future astrometric observations with MAVIS and MAORY.

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Section: Tip-tilt Anisoplanatism In Mcao-assisted Astrometric Observa...mentioning

confidence: 99%

Temporal spectrum of multiconjugate adaptive optics residuals and impact of tip-tilt anisoplanatism on astrometric observations

Carlà

Plantet

Busoni

et al. 2022

Monthly Notices of the Royal Astronomical Society

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“…Flicker presented a linear model for the change in tip-tilt across the field as a result of the three high-altitude focus and astigmatism (the so-called "plate-scale" modes). 21 By making three off-axis tip-tilt measurements, we can estimate five terms (on-axis tip-tilt and the plate scale modes).…”

Section: Tip-tilt Sensing With Multiple Starsmentioning

confidence: 99%

Infrared tip-tilt sensing: on-sky experience, lessons learned and unsolved problems

Dam¹,

Oberti²,

Kolb³

et al. 2022

Preprint

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Infrared tip-tilt sensors (IR TTSs) have been deployed on three different laser guide star adaptive optics (AO) systems on three different telescopes. These IR TTS benefit from the high-order loop PSF sharpening in the near infrared, hence they provide a low tip-tilt residual and a good sky coverage. Nevertheless, these IR TTS are challenging and their use in AO is limited. In this paper, we outline existing IR TTS, provide on-sky performance results and describe our experience using IR TTS and along with plans for the near future. The second part of the paper deals with unresolved challenges for IR TTS. These include algorithms and loop stability in the low Strehl regime, using IR TTSs to measure higher-order modes and guiding on multiple guide stars with different magnitudes.

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“…B ⊥ refers to uncompensated spatial frequencies while B include AO residual only and B∆ corresponds to the anisoplanatism effect. The calculation of this latter can be found in multiple references (Beltramo-Martin et al 2018;Britton 2006;Flicker et al 2003;Fusco et al 2000;Whiteley et al 1998). In the case of SPHERE/ZIMPOL, we must only account for angular anisoplanatism that is produced by the spatial decorrelation of the incoming wavefront.…”

Section: Reconstructing the Psfmentioning

confidence: 99%

“…The aliasing covariance function is derived from a model of the aliasing PSD WAL (Correia & Teixeira 2014;Jolissaint 2010;Flicker 2008) that accounts for the spatial filtering of the Shack-Hartmann WFS and the temporal propagation of the aliased measurement through the AO loop. Eventually we have…”

Section: Reconstruction Of the Aliasingmentioning

confidence: 99%

Pushing point-spread function reconstruction to the next level: application to SPHERE/ZIMPOL

Beltramo-Martin

Marasco

Fusco

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Point spread function (PSF) reconstruction (PSF-R) is a well established technique to determine reliably and accurately the PSF from Adaptive Optics (AO) control loop data. We have successfully applied this technique to improve the precision on photometry and astrometry to observation of NGC6121 obtained with SPHERE/ZIMPOL as it will be presented in a forthcoming letter. Firstly, we present the methodology we followed to reconstruct the PSF combining pupil-plane and focal-plane measurements using using our PSF-R method PRIME (Beltramo-Martin et al. 2019), with upgrade of both the model and best-fitting steps compared to previous papers. Secondly, we highlight that PRIME allows to maintain the PSF fitting residual below 0.2% over 2 hours of observation and using only 30 s of AO telemetry, which may have important consequences for telemetry storage for PSF-R purpose on future 30-40 m class telescopes. Finally, we deploy PRIME in a more realistic regime using faint stars so as to identify the precision needed on the initial guess parameters to ensure the convergence towards the optimal solution.

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Tilt anisoplanatism in laser-guide-star-based multiconjugate adaptive optics

Cited by 16 publications

References 17 publications

Temporal spectrum of multiconjugate adaptive optics residuals and impact of tip-tilt anisoplanatism on astrometric observations

Temporal spectrum of multiconjugate adaptive optics residuals and impact of tip-tilt anisoplanatism on astrometric observations

Infrared tip-tilt sensing: on-sky experience, lessons learned and unsolved problems

Pushing point-spread function reconstruction to the next level: application to SPHERE/ZIMPOL

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