Adaptive optics or numerical restoration algorithms that restore high resolution imaging through atmospheric turbulence are subject to isoplanatic wave-front errors. Mitigating those errors requires that the wave-front aberrations be estimated within the 3D volume of the atmosphere. Present techniques rely on multiple beacons, either natural stars or laser guide stars, to probe the atmospheric aberration along different lines of sight, followed by tomographic projection of the measurements onto layers at defined ranges. In this paper we show that a three-dimensional estimate of the wave-front aberration can be recovered from measurements by a single guide star in the case where the aberration is stratified, provided that the telescope tracks across the sky with non-uniform angular velocity. This is generally the case for observations of artificial earth-orbiting satellites, and the new method is likely to find application in ground based telescopes used for space situational awareness.

We report contrast measurements of a sodium resonance guide star against the daylight sky when observed through a tuned magneto-optical filter (MOF). The guide star was created by projection of a laser beam at 589.16 nm into the mesospheric sodium layer and the observations were made with a collocated 1.5-m telescope. While MOFs are used with sodium light detecting and ranging systems during the day to improve the signalto- noise ratio of the measurements, they have not so far been employed with laser guide stars to drive adaptive optics (AO) systems to correct atmospherically induced image blur. We interpret our results in terms of the performance of AO systems for astronomy, with particular emphasis on thermal infrared observations at the next generation of extremely large telescopes now being built. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

We report photometric measurements of a sodium resonance guide star against the daylight sky when observed through a tuned magneto-optical filter (MOF). The MOF comprises a sodium vapor cell in a kilogauss-level magnetic field between crossed polarizers and has a very narrow transmission profile at the sodium D-2 resonance of approximately 0.008 nm. Our observations were made with the 1.5 m Kuiper telescope on Mt. Bigelow, AZ, which has a separately mounted guide star laser projecting a circularly polarized single-frequency beam of approximately 6.5 W at 589.16 nm. Both the beam projector and the 1.5 m telescope were pointed close to zenith; the baseline between them is approximately 5 m. Measurements of the guide star were made on the morning of 2016 March 24 using an imaging camera focused on the beacon and looking through the full aperture of the telescope. The guide star flux was estimated at 1.20x10(6) photon/m(2)/s while at approximately 45 minutes after sunrise, the sky background through the MOF was 1100 photon/m(2)/s/arcsec(2). We interpret our results in terms of thermal infrared observations with adaptive optics on the next generation of extremely large telescopes now being built.

Fluctuations in accommodation have been shown to be correlated in the two eyes of the same subject. However, the dynamic correlation of higher-order aberrations in the frequency domain has not been studied previously. A binocular Shack-Hartmann wavefront sensor is used to measure the ocular wavefront aberrations concurrently in both eyes of six subjects at a sampling rate of 20.5 Hz. Coherence function analysis shows that the inter-ocular correlation between aberrations depends on subject, Zernike mode and frequency. For each subject, the coherence values are generally low across the resolvable frequency range (mean 0.11), indicating poor dynamic correlation between the aberrations of the two eyes. Further analysis showed that phase consistency dominates the coherence values. Monocular and binocular viewing conditions showed similar power spectral density functions.

L'observation directe des exoplanètes est rendue difficile par l'énorme contraste entre la planète et l'étoile autour de laquelle elle gravite, ainsi que la faible séparation angulaire entre ces deux corps. Un tel niveau de contraste aussi proche de l'étoile être atteint en couplant l'imagerie à haute résolution angulaire et la coronographie, qui atténue le flux en provenance de l'étoile ; les performances ultimes d'un instrument d'imagerie à haut contraste sont alors limitées par ses aberrations quasi-statique. Au cours de cette thèse a été conçu un ASO plan focal dédié à la calibration des aberrations quasi-statiques dans les systèmes d'imagerie à haut contraste. Cet ASO, baptisé COFFEE, permet d'estimer les aberrations en amont et en aval du coronographe à partir d'images coronographiques acquises en plan focal différant d'une phase de diversité connue introduite en amont du coronographe. Au cours de cette thèse, COFFEE a été conçu et validé par simulations numérique et démontré expérimentalement sur banc. L'identification de plusieurs facteurs limitant la précision de l'estimation des aberrations a ensuite induit une modification du formalisme sur lequel repose COFFEE pour l'adapter à l'estimation d'aberrations de hautes fréquences spatiales avec une précision nanométrique. Cette version hauts ordres de COFFEE a été utilisée avec succès sur l'instrument SPHERE, où la compensation des aberrations estimées par COFFEE a permis d'optimiser le contraste. Enfin, une nouvelle méthode de compensation a été développée pour permettre d'atteindre de très hauts niveaux de contraste sur le détecteur scientifique. / Performing an exoplanet direct detection means being able to image an object as faint as an extra-solar planet very close to its parent star. After compensation of the turbulence by the XAO loop and most of the star light removed by a coronagraph, the ultimate limitation of high contrast imaging systems lies in its quasi-static aberrations that creates a residual signal which limit the achievable contrast on the scientific detector. To increase the achievable contrast on the detector, these aberrations must be compensated for, ideally using focal plane data recorded from the scientific detector to avoid differential aberrations. The aim of this thesis was to develop a focal-plane wavefront sensor (WFS) dedicated to the estimation of quasi-static aberrations in high contrast imaging systems. This WFS, called COFFEE, estimates the aberrations both upstream and downstream of the coronagraph using coronagraphic focal plane images that differ from a known diversity aberrations introduced upstream of the coronagraph. During this research work, COFFEE has been developed, tested using numerical simulations and demonstrated on an in-house bench. Considering the limitations of the estimation accuracy, COFFEE's formalism has then been modified to allow it to estimate high frequencies aberrations with nanometric precision. This extended version of COFFEE has been successfully used on SPHERE to optimize the contrast on the scientific detector of the instrument using COFFEE in a dedicated compensation process. Lastly, a new compensation method has been developed in order to reach very high contrast levels on the scientific detector.