Study of the atmospheric refraction in a single mode instrument - Application to AMBER/VLTI

International audienceThis paper presents a study of the atmospheric refraction and its effect on the light coupling efficiency in an instrument using single-mode optical fibers. 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 (VLTI), but most of the conclusions can be generalized to other single-mode instruments. We used the software package caos (Code for Adaptive Optics Systems) to take into account the atmospheric turbulence effect after correction by the ESO system MACAO (Multi-Application Curvature Adaptive Optics). The opto-mechanical 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, alpha 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

European Journal of Physics A new radiation pressure formula to calculate the optical force exerted by a laser on a trapped particle

International audienceAbstract. This letter proposes a new expression of the radiation pressure force exerted by light on any piece of matter. This expression defines the optical force on any macroscopic particle surrounded by an isotropic fluid. It is restricted to quasi-permanent light illumination of the scatterer, where the usual tensors of Minkovsky and Abraham become equivalent. As experimentd and numerical aspects of this approach were previously developed, I focus here on the derivation of this new formula from Maxwell theory.Résumé. Cette lettre propose une nouvelle expression de la force de pression de radiation exercée par la Iumière sur la matière. Cette expression définiit la force optique exercée sur toute particule macroscopique entourée d'un fluide isotrope. Elle concerne un éclairement quasi-permanent de I'objet diffusant, où les tenseurs habituels de Minkovsky et Abraham deviennent équivalents. Puisque les aspects expérimentaux et numériques de cette approche ont déjà été développés, je présente ici comment cette nouvelle formule découle de la théorie de Maxwell

Recent Progress in Lunar Laser Ranging at Grasse Laser Ranging Station

International audienceBased on a fully passive space segment, the Lunar Laser Ranging experiment is the last of the Apollo Lunar Surface Experiments Package to operate. Observations from Grasse Lunar Laser Ranging station have been realized on a daily basis since the first echoes obtained in 1981. We will give a brief summary of the progress made at Grasse Laser Ranging facility (Observatoire de la Côte d'Azur, Calern Plateau on the french riviera) since the first echoes. The current performances, driven by the use of infrared wavelength, are presented for the year 2018. The capacities of Grasse Lunar Laser Ranging station have been clearly improved in terms of budget link, reflectors numbers and synodic period observation

Recent Progress in Lunar Laser Ranging at Grasse Laser Ranging Station

International audienceBased on a fully passive space segment, the lunar laser ranging experiment is the last of the Apollo Lunar Surface Experiments Package to operate. Observations from the Grasse lunar laser ranging station have been made on a daily basis since the first echoes obtained in 1981. In this paper, first, we review the principle and the technical aspects of lunar laser ranging. We then give a brief summary of the progress made at the Grasse laser ranging facility (Observatoire de la Côte d'Azur, Calern Plateau on the French Riviera) since the first echoes. The current performance, driven by the use of an infrared wavelength laser, is presented in the last section for the year 2018

Recent Progress in Lunar Laser Ranging at Grasse Laser Ranging Station

International audienceBased on a fully passive space segment, the Lunar Laser Ranging experiment is the last of the Apollo Lunar Surface Experiments Package to operate. Observations from Grasse Lunar Laser Ranging station have been realized on a daily basis since the first echoes obtained in 1981. We will give a brief summary of the progress made at Grasse Laser Ranging facility (Observatoire de la Côte d'Azur, Calern Plateau on the french riviera) since the first echoes. The current performances, driven by the use of infrared wavelength, are presented for the year 2018. The capacities of Grasse Lunar Laser Ranging station have been clearly improved in terms of budget link, reflectors numbers and synodic period observation

Demonstration of deep-space synchronous two-way laser ranging with a laser transponder aboard Hayabusa2

International audienc

AMBER: the near-infrared focal instrument for the Very Large Telescope Interferometer

International audienceAMBER is a focal instrument for the Very Large Telescope Interferometer working in the near infrared from 1.1 to 2.4 micrometers . It has been designed having in mind the General User of interferometric observations and the full range of his possible astrophysical programs. However the three programs used to define the key specifications have been the study of Young Stellar Objects, the study of Active Galactic Nuclei dust tori and broad line regions and the measure of masses and spectra of hot Extra Solar Planets. AMBER combines up to three beams produced by the VLTI 8 m Unit Telescopes equipped with Adaptive Optics and/or by the 1.8 m Auxiliary Telescopes. The fringes are dispersed with resolutions ranging from 35 to 10000. It is optimized for high accuracy single mode measurements of the absolute visibility, of the variation of the visibility and phase with wavelength (differential interferometry) and of phase closure relations with three telescopes. The instrument and its software are designed to allow a highly automated user friendly operation and an easy maintenance