397 research outputs found

    Laboratory Testing the Layer Oriented Wavefront Sensor for the Multiconjugate Adaptive optics Demonstrator

    Full text link
    The Multiconjugate Adaptive optics Demonstrator (MAD) for ESO-Very Large Telescopes (VLT) will demonstrate on sky the MultiConjugate Adaptive Optics (MCAO) technique. In this paper the laboratory tests relative to the first preliminary acceptance in Europe of the Layer Oriented (LO) Wavefront Sensor (WFS) for MAD will be described: the capabilities of the LO approach have been checked and the ability of the WFS to measure phase screens positioned at different altitudes has been experimented. The LO WFS was opto-mechanically integrated and aligned in INAF - Astrophysical Observatory of Arcetri before the delivering to ESO (Garching) to be installed on the final optical bench. The LO WFS looks for up to 8 reference stars on a 2arcmin Field of View and up to 8 pyramids can be positioned where the focal spot images of the reference stars form, splitting the light in four beams. Then two objectives conjugated at different altitudes simultaneously produce a quadruple pupil image of each reference star.Comment: 12 pages,14 figures, Proceeding of Spie Conference "Advances in Adaptive Optics II", Orlando 200

    The opto-mechanical alignment procedure of the VLT Survey Telescope

    Full text link
    The VLT Survey Telescope is a f/5.5 modified Ritchey-Chretien imaging telescope, which is being installed at the ESO-Paranal Observatory. It will provide a one square degree corrected field of view to perform survey-projects in the wavelength range from UV to I band. In this paper we describe the opto-mechanical alignment procedure of the 2.61m primary mirror, the secondary and correctors lenses onto the mechanical structure of the telescope. The alignment procedure does not rely on the mechanical precision of the mirrors. It will be achieved using ad-hoc alignment tools, described in the paper, which allows the spatial determination of optical axes (and focuses where necessary) of the optical components with respect to the axis defined by the rotation of a laser beam mounted on the instrument bearing.Comment: 10 pages, 10 figures, Proceeding 773357 of the SPIE Conference "Ground-based and Airborne Telescopes III", Sunday 27 June 2010, San Diego, California, US

    Is There a Place in the World for Zoos? / Another View of Zoos

    Get PDF
    We human animals make rapid technological and cultural advancements because we have the ability to pass definitive information to succeeding generations. But we also accept too much from the past without challenge. The good, the bad, and the indifferent are muddled together, accumulating in layers that smother each succeeding age. Cultural mores ranging from the silly to the profane, from charming to dangerous, clutter our world. They exist only because, as the British are wont to say, “We have always done things this way.” One very troubling example is the public zoological parks found in almost every city: they are fundamentally unchanged from the first public zoo that opened in The Regent’s Park in London in 1828. Although significant modifications have taken place since then, particularly recently, for the most part, zoos continue to do things the way they have done them for almost two centuries. An objective reevaluation is long overdue

    Is There a Place in the World for Zoos? / Another View of Zoos

    Get PDF
    We human animals make rapid technological and cultural advancements because we have the ability to pass definitive information to succeeding generations. But we also accept too much from the past without challenge. The good, the bad, and the indifferent are muddled together, accumulating in layers that smother each succeeding age. Cultural mores ranging from the silly to the profane, from charming to dangerous, clutter our world. They exist only because, as the British are wont to say, “We have always done things this way.” One very troubling example is the public zoological parks found in almost every city: they are fundamentally unchanged from the first public zoo that opened in The Regent’s Park in London in 1828. Although significant modifications have taken place since then, particularly recently, for the most part, zoos continue to do things the way they have done them for almost two centuries. An objective reevaluation is long overdue

    An update of the on-sky performance of the Layer-Oriented wave-front sensor for MAD

    Full text link
    The Multi-conjugate Adaptive optics Demonstrator, MAD, successfully demonstrated on sky the MCAO technique both in Layer Oriented and Star Oriented modes. As results of the Guaranteed Time Observations in Layer Oriented mode quality astronomy papers have been published. In this paper we concentrate on the instrumentation issues and technical aspects which stay behind this success.Comment: 12 pages, 10 figures, Proceedings of the SPIE conference "Adaptive Optics Systems II", 27 June 2010, San Diego, California, US

    Simulations of ELT-GMCAO performance for deep field observations

    Get PDF
    The Global-Multi Conjugated Adaptive Optics (GMCAO) approach offers an alternative way to correct an adequate scientific Field of View (FoV) using only natural guide stars (NGSs) to extremely large ground-based telescopes. Thus, even in the absence of laser guide stars, a GMCAO-equipped ELT-like telescope can achieve optimal performance in terms of Strehl Ratio (SR), retrieving impressive results in studying star-poor fields, as in the cases of the deep field observations. The benefits and usability of GMCAO have been demonstrated by studying 6000 mock high redshift galaxies in the Chandra Deep Field South region. However, a systematic study simulating observations in several portions of the sky is mandatory to have a robust statistic of the GMCAO performance. Technical, tomographic and astrophysical parameters, discussed here, are given as inputs to GIUSTO, an IDL-based code that estimates the SR over the considered field, and the results are analyzed with statistical considerations. The best performance is obtained using stars that are relatively close to the Scientific FoV; therefore, the SR correlates with the mean off-axis position of NGSs, as expected, while their magnitude plays a secondary role. This study concludes that the SRs correlate linearly with the galactic latitude, as also expected. Because of the lack of natural guide stars needed for low-order aberration sensing, the GMCAO confirms as a promising technique to observe regions that can not be studied without the use of laser beacons. It represents a robust alternative way or a risk mitigation strategy for laser approaches on the ELTs.Comment: 18 pages, 10 figures, accepted for publication on PAS

    Numerical control matrix rotation for the LINC-NIRVANA Multi-Conjugate Adaptive Optics system

    Full text link
    LINC-NIRVANA will realize the interferometric imaging focal station of the Large Binocular Telescope. A double Layer Oriented multi-conjugate adaptive optics system assists the two arms of the interferometer, supplying high order wave-front correction. In order to counterbalance the field rotation, mechanical derotation for the two ground wave-front sensors, and optical derotators for the mid-high layers sensors fix the positions of the focal planes with respect to the pyramids aboard the wave-front sensors. The derotation introduces pupil images rotation on the wavefront sensors: the projection of the deformable mirrors on the sensor consequently change. The proper adjustment of the control matrix will be applied in real-time through numerical computation of the new matrix. In this paper we investigate the temporal and computational aspects related to the pupils rotation, explicitly computing the wave-front errors that may be generated.Comment: 6 pages, 2 figures, presented at SPIE Symposium "Astronomical Telescopes and Instrumentation'' conference "Adaptive Optics Systems II'',Sunday 27 June 2010, San Diego, California, US

    Hierarchichal-segmented AO in order to attain wide field compensation in the visible on an 8m class telescope

    Full text link
    We describe the preliminary optimized layout for a partially optimized concept of an optical-8m class VLT-like 2x2 segmented camera where each channel is assisted by an equivalent of an MCAO system where the ground layer correction is commonly employed while the high altitude ones is performed in an open-loop fashion. While we derive the basic relationships among the Field of View and attainable correction with a pre-defined choice for the hardware, we discuss sky coverage and wavefront sensing issues employing natural and artificial references, involving the latest stateof-the-art in the development of wavefront sensing. We show that a flexible approach allow for a compensated Field of View that is variable and can be properly tuned matching the current turbulence situation and the requirement in term of quality of the compensation. A preliminary description of the overall optomechanical package is given as well along with a rough estimates of the efforts required to translates such a concept into reality.Comment: 6 pages, 4 figures, in AO4ELT5 Proceeding
    • …
    corecore