Browsing by Author "Neichel, B."
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- ItemAn integrated MASS/DIMM monitor based on a low-noise CCD detector(2015) Guesalaga Meissner, Andrés Rodrigo; Osborn, J.; Sarazin, M.; Neichel, B.; Perera, S.; Wilson, R.; Wizinowich, PeterWe propose a novel design for a turbulence profiler. Using a single detector, images of the pupil (scintillation) and stars (image motion) are formed in the detector plane. The instrument is called FASS (Full Aperture Scintillation Sensor), as it uses the full aperture of the telescope. Different processing strategies are evaluated, including spatial segmentation and Fourier analysis. The different approaches are tested via simulation and on-sky data from two telescopes and compared to profiles obtained with the Durham Stereo-SCIDAR monitor. Overall, simulations shows that the method is more accurate that the classical MASS configuration, but it is shown that the photon noise plays an important role in the accuracy of the method, imposing stringent requirements on the pixel size, which must be significantly smaller than the speckle size formed from turbulence close to the ground (Fresnel law for speckle size).
- ItemBeam shaping for laser-based adaptive optics in astronomy(2014) Bechet, Clementine Marie Zelia; Guesalaga Meissner, Andrés; Neichel, B.; Fesquet, V.; González Núñez, Héctor; Zuñiga, S.; Escarate, P.; Guzmán Carmine, Christian Dani
- ItemEffect of the influence function of deformable mirrors on laser beam shaping(2017) González Núñez, Héctor; Bechet, Clementine Marie Zelia; Ayancan, B.; Neichel, B.; Guesalaga Meissner, Andrés
- ItemExpected performance of the Pyramid wavefront sensor with a laser guide star for 40 m class telescopes(2024) Oyarzun, F.; Chambouleyron, V.; Neichel, B.; Fusco, T.; Guesalaga, A.Context. The use of artificial laser guide stars (LGS) is planned for the new generation of giant segmented mirror telescopes in order to extend the sky coverage of their adaptive optics systems. The LGS, being a 3D object at a finite distance, will have a large elongation that will affect its use with the Shack-Hartmann (SH) wavefront sensor. Aims. In this paper, we compute the expected performance for a Pyramid WaveFront Sensor (PWFS) using an LGS for a 40 m telescope affected by photon noise, and also extend the analysis to a flat 2D object as reference. Methods. We developed a new way to discretize the LGS, and a new, faster method of propagating the light for any Fourier filtering wavefront sensors (FFWFS) when using extended objects. We present the use of a sensitivity model to predict the performance of a closed-loop adaptive optic system. We optimized a point-source-calibrated interaction matrix to accommodate the signal of an extended object by computing optical gains using a convolutional model. Results. We find that the sensitivity drop, given the size of the extended laser source, is large enough to make the system operate in a low-performance regime given the expected return flux of the LGS. The width of the laser beam is identified as the limiting factor, rather than the thickness of the sodium layer. Even an ideal, flat LGS will have a drop in performance due to the flux of the LGS, and small variations in the return flux will result in large variations in performance. Conclusions. We conclude that knife-edge-like wavefront sensors, such as the PWFS, are not recommended for use with LGS for a 40 m telescope, as they will operate in a low-performance regime, given the size of the extended object.
- ItemMitigation of vibrations in adaptive optics by minimization of closed-loop residuals(2013) Guesalaga Meissner, Andrés; Neichel, B.; O'Neal, J.; Guzmán Ángel, Daniela
- ItemOnline estimation of the wavefront outer scale profile from adaptive optics telemetry(2017) Guesalaga Meissner, Andrés; Neichel, B.; Correia, C.; Butterley, T.; Osborn, J.; Masciadri, E.; Fusco, T.; Sauvage, J.
- ItemTowards an automatic wind speed and direction profiler for Wide Field adaptive optics systems(2018) Sivo, G.; Turchi, A.; Masciadri, E.; Guesalaga Meissner, Andrés; Neichel, B.
- ItemValidation through simulations of a C-n(2) profiler for the ESO/VLT Adaptive Optics Facility(2015) García Rissmann, A.; Guesalaga Meissner, Andrés; Kolb, J.; Le Louarn, M.; Madec, P.-Y.; Neichel, B.