Study of the atmospheric refraction in a single-mode instrument – application to AMBER/VLTI |
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| Authors: | S Robbe-Dubois S Lagarde Y Bresson R G Petrov M Carbillet E LeCoarer F Rantakyrö I Tallon-Bosc M Vannier P Antonelli G Martinot-Lagarde A Roussel D Tasso |
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| Institution: | Laboratoire Fizeau, Universitéde Nice Sophia-Antipolis, Observatoire de la Côte d'Azur, CNRS, UMR 6525, Parc Valrose, 06108 Nice cedex 2, France;Laboratoire d'Astrophysique Observatoire de Grenoble, UniversitéJ. Fourier, CNRS, UMR 5571, 414 rue de la piscine, 38041 Grenoble cedex 9, France;Gemini Observatory Southern Operations Center, c/o AURA, Casilla 603, La Serena, Chile;European Southern Observatory, Casilla 19001, Santiago 19, Chile;Universitéde Lyon, 69003 Lyon, France;UniversitéLyon 1, Observatoire de Lyon, 9 Av. Charles André, 69230 Saint Genis Laval, France;CNRS, UMR 5574, Centre de Recherche Astrophysique de Lyon;Ecole Normale Supérieure de Lyon, 69007 Lyon, France;Laboratoire Géosciences Azur, Universitéde Nice Sophia-Antipolis, Observatoire de la Côte d'Azur, CNRS, UMR 6526, Av. Nicolas Copernic, 06130 Grasse, France;Division Technique INSU/CNRS UPS 855, 1 place Aristide Briand, 92195 Meudon cedex, France |
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| Abstract: | This paper presents a study of the atmospheric refraction and its effect on the light coupling efficiency in an instrument using single-mode optical fibres. We show the analytical approach which allowed us to assess the need to correct the refraction in J and H bands while observing with an 8-m Unit Telescope. We then developed numerical simulations to go further in calculations. The hypotheses on the instrumental characteristics are those of AMBER (Astronomical Multi BEam combineR), the near-infrared focal beam combiner of the Very Large Telescope Interferometric mode, but most of the conclusions can be generalized to other single-mode instruments. We used the software package caos to take into account the atmospheric turbulence effect after correction by the European Southern Observatory system Multi-Application Curvature Adaptive Optics. The optomechanical study and design of the system correcting the atmospheric refraction on AMBER is then detailed. We showed that the atmospheric refraction becomes predominant over the atmospheric turbulence for some zenith angles z and spectral conditions: for z larger than 30° in J band for example. The study of the optical system showed that it allows to achieve the required instrumental performance in terms of throughput in J and H bands. First observations in J band of a bright star, α Cir star, at more than 30° from zenith clearly showed the gain to control the atmospheric refraction in a single-mode instrument, and validated the operating law. |
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| Keywords: | atmospheric effects instrumentation: high angular resolution instrumentation: interferometers methods: laboratory methods: numerical |
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