Download or read book Analyse de surface d onde pour le contr le actif d un t lescope spatial written by Ludovic Meynadier and published by . This book was released on 1998 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book ANALYSE DE SURFACE D ONDE POUR LE CONTROLE ACTIF D UN TELESCOPE SPACIAL written by Ludovic Meynadier and published by . This book was released on 1997 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: LES GRANDS TELESCOPES SUBISSENT DES PERTURBATIONS, COMME LES DEFORMATIONS DE LA STRUCTURE DE L'INSTRUMENT, QUI DEGRADENT LES OBSERVATIONS ET QU'UN SYSTEME D'OPTIQUE ACTIVE PEUT COMPENSER GRACE A LA MESURE DES ABERRATIONS PAR UN ANALYSEUR DE SURFACE D'ONDE. PARMI LES NOMBREUX ANALYSEURS EXISTANTS, NOUS NOUS SOMMES INTERESSES A LA TECHNIQUE DE DIVERSITE DE PHASE QUI UTILISE LA CONNAISSANCE DE LA REPARTITION D'INTENSITE DES IMAGES DANS PLUSIEURS PLANS PROCHES DU PLAN FOCAL. LA DIVERSITE DE PHASE SEMBLE BIEN ADAPTE AUX INSTRUMENTS DEDIES A L'OBSERVATION DE LA TERRE DEPUIS L'ESPACE, DU FAIT DE SA FACILITE DE MISE EN UVRE. POURTANT LES PERFORMANCES DE CET ANALYSEUR, PROPOSE IL Y A QUELQUES ANNEES, N'ONT ENCORE JAMAIS ETE CARACTERISEES CAR IL NECESSITE UNE METHODE DE TRAITEMENT DES DONNEES COMPLEXE. NOUS AVONS EFFECTUE UNE ETUDE EXHAUSTIVE DU COMPORTEMENT DE LA DIVERSITE DE PHASE, POUR DEMONTRER QU'ELLE PEUT ETRE UNE ALTERNATIVE AUX SOLUTIONS EXISTANTES. NOUS AVONS EN PREMIER LIEU REALISE UNE ETUDE THEORIQUE DE L'INFLUENCE DU BRUIT DE MESURE SUR L'ESTIMATION DE LA PHASE. CETTE ETUDE A ENSUITE ETE ETENDUE PAR SIMULATION NUMERIQUE AU FONCTIONNEMENT EN LUMIERE BLANCHE, CET ANALYSEUR ETANT SENSIBLE AUX EFFETS CHROMATIQUES, AUX EFFETS DE LA SOUS-MODELISATION DE LA PHASE ABERRANTE LORS DE LA MESURE, ET AU GAIN APPORTE PAR UNE REGULARISATION DE LA PHASE LORSQUE L'ON DISPOSE D'UNE CONNAISSANCE A PRIORI DE CELLE-CI. CES RESULTATS ONT ETE CONFIRMES DE MANIERE EXPERIMENTALE, AVANT DE FAIRE L'APPLICATION DE LA DIVERSITE DE PHASE EN OPTIQUE ACTIVE ET DE LA COMPARER A L'ANALYSEUR DE HARTMANN-SHACK AU COMPORTEMENT BIEN CONNU. CE TRAVAIL A PERMIS DE MONTRER QUE LA DIVERSITE DE PHASE PERMET, AVEC UN DISPOSITIF TRES SIMPLE, DE FAIRE DES MESURES PRECISES A PARTIR DE SOURCES ETENDUES POLYCHROMATIQUES, ET SURTOUT QU'ELLE PRESENTE TOUTES LES QUALITES NECESSAIRES POUR ASSURER LE CONTROLE ACTIF D'UN INSTRUMENT EMBARQUE A BORD D'UN SATELLITE.
Download or read book Analyse de surface d onde pour le contr l actif d un t lescope spatial written by Ludovic Meynadier and published by . This book was released on 1998 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optique active spatiale pour l observation haute r solution written by Clément Escolle and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pour relever les défis de l'observation de la Terre et de l'astronomie, les futurs observatoires spatiaux vont requérir des télescopes de plusieurs mètres de diamètre. Les différentes contraintes liées à l'environnement spatial vont induire des déformations et des désalignements des miroirs du télescope dégradant ainsi la qualité optique des observations. L'intégration de l'optique active, utilisée depuis la fin des années 80 pour l'alignement et le maintien de la qualité optique des télescopes au sol, devient donc nécessaire. Un tel système est constitué de trois éléments : un dispositif de mesure, une fonction de correction et une boucle de contrôle qui fait le lien entre les deux éléments précédents.Les travaux de recherche présentés dans ce mémoire de doctorat s'attachent, d'une part, au développement d'un estimateur des perturbations minimisant le front d'onde résiduel dans le champ du télescope. L'analyse de cet estimateur et plus généralement des performances ultimes d'un système d'optique active spatial nous a permis de mettre en évidence l'impact des hautes fréquences spatiales sur la qualité optique. La présence de telles hautes fréquences dues à l'empreinte des supports du miroir primaire nous a poussés, d'autre part, à évaluer les possibilités de leur réduction dans le cas d'un miroir de grande dimension. A l'aide d'une modélisation éléments finis d'un tel miroir nous avons réalisé des modifications locales de la structure du miroir pour adapter ses déformations aux capacités de correction de l'optique active.
Download or read book Comparaison des techniques d analyse de surface d onde en plan focal d di es aux missions spatiales d imagerie directe et de spectroscopie des plan tes extrasolaires written by Axel Potier and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprendre la formation, l'évolution et la surprenante diversité des planètes extrasolaires est un des grands enjeux de l'astrophysique moderne. En deux décennies, de nombreuses découvertes ont déjà révélé la nature complexe de plus de 4000 objets. Pourtant, on connaît peu de choses sur l'atmosphère de ces planètes alors qu'il s'agit d'un point crucial pour déterminer les conditions d'apparition de la vie ailleurs que sur Terre. L'imagerie directe est une technique appropriée à l'étude spectrale des atmosphères d'exoplanètes similaires à celles du Système Solaire.L'imagerie des exoplanètes est cependant limitée par le très grand contraste et par la proximité entre exoplanètes et étoiles. Des techniques optimisées pour l'imagerie à très haute dynamique telles que la coronographie sont donc indispensables. Les coronographes atténuent la lumière des étoiles sans affecter le signal provenant de leurs environnements proches pour le révéler. Cependant, la turbulence atmosphérique, ainsi que les défauts de polissage, les erreurs d'alignement et les dilatations thermiques des télescopes qui peuvent varier avec le temps limitent encore leurs performances. Des techniques de correction active d'aberrations composées de miroirs déformables et d'analyseurs de front d'onde équiperont alors les futurs instruments haute-dynamiques tels que les projets spatiaux WFIRST, HaBEX ou LUVOIR ou encore les instruments aux foyers des Extremely Large telescopes.L'instrument Très Haute Dynamique 2 (THD2) situé à l'Observatoire de Paris/LESIA est un banc de test dédié à ce type d'activité. Durant cette thèse, plusieurs algorithmes d'analyse et de contrôle du front d'onde développés par différentes équipes en Europe et aux États-Unis ont été testés et comparés dans les mêmes conditions de stabilité sur le THD2. Lors de ces tests, la technique d'analyse pair-wise associée à une technique de conjugaison du champ électrique a d'ailleurs démontré d'excellentes performances en contraste dans des conditions spatiales, sans aucune modification du design optique de l'instrument. Fort de cette expérience, cette méthode a alors été implémentée sur l'instrument haute-dynamique VLT/SPHERE dont les résultats sur source interne laissent entrevoir des améliorations en contraste de plusieurs ordres de grandeur.
Download or read book Mod lisation des effets de l chelle externe de coh rence spatiale du front d onde pour l observation haute r solution angulaire en astronomie written by Rodolphe Conan and published by . This book was released on 2000 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Les performances des instruments dédiés à la Haute Résolution Angulaire (HRA) sont sévèrement limitées par les effets de la turbulence atmosphérique. Une analyse spatio-temporelle de la phase de l'onde incidente est indispensable à l'optimisation des techniques telles que l'optique adaptative et l'interférométrie à longues bases. Parmi les paramètres les mieux connus permettant de quantifier la dégradation des surfaces d'onde par la turbulence atmosphérique, nous connaissons le paramètre de Fried et l'angle d'isoplanétisme. Avec l'avènement des nouveaux interféromètres et des grands téléscopes, la connaissance d'un nouveau paramètre, l'échelle externe, est maintenant devenu indispensable à la caractérisation d'un site astronomique. L'influence de la valeur finie de l'échelle externe sur les techniques de la HRA est le thème central de la thèse qui présente les outils mathématiques et les solutions à plusieurs intégrales utiles aux modélisations des effets de l'échelle externe en HRA, puis examine les traitements théoriques des effets de l'échelle externe en HRA et donne les résultats des différentes campagnes de mesures effectuées avec le Generalized Seeing Monitor (GSM). (...) À travers ce travail, il apparaît que l'échelle externe est un paramètre dont la connaissance est indispensable à l'optimisation des futurs instruments en HRA (...)
Download or read book Information Bulletin written by and published by . This book was released on 1991 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2004 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Lenses and Waves written by Fokko Jan Dijksterhuis and published by Springer Science & Business Media. This book was released on 2006-01-20 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1690, Christiaan Huygens (1629-1695) published Traité de la Lumière, containing his renowned wave theory of light. It is considered a landmark in seventeenth-century science, for the way Huygens mathematized the corpuscular nature of light and his probabilistic conception of natural knowledge. This book discusses the development of Huygens' wave theory, reconstructing the winding road that eventually led to Traité de la Lumière. For the first time, the full range of manuscript sources is taken into account. In addition, the development of Huygens' thinking on the nature of light is put in the context of his optics as a whole, which was dominated by his lifelong pursuit of theoretical and practical dioptrics. In so doing, this book offers the first account of the development of Huygens' mathematical analysis of lenses and telescopes and its significance for the origin of the wave theory of light. As Huygens applied his mathematical proficiency to practical issues pertaining to telescopes – including trying to design a perfect telescope by means of mathematical theory – his dioptrics is significant for our understanding of seventeenth-century relations between theory and practice. With this full account of Huygens' optics, this book sheds new light on the history of seventeenth-century optics and the rise of the new mathematical sciences, as well as Huygens' oeuvre as a whole. Students of the history of optics, of early mathematical physics, and the Scientific Revolution, will find this book enlightening.
Download or read book European Russian Space Cooperation written by Brian Harvey and published by Springer Nature. This book was released on 2021-04-10 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: The story of European-Russian collaboration in space is little known and its importance all too often understated. Because France was the principal interlocutor between these nations, such cooperation did not receive the attention it deserved in English-language literature. This book rectifies that history, showing how Russia and Europe forged a successful partnership that has continued to the present day. Space writer Brian Harvey provides an in-depth picture of how this European-Russian relationship evolved and what factors—scientific, political and industrial—propelled it over the decades. The history begins in the cold war period with the first collaborative ventures between the Soviet Union and European countries, primarily France, followed later by Germany and other European countries. Next, the chapters turn to the missions when European astronauts flew to Russian space stations, the Soyuz rocket made a new home in European territory in the South American jungle and science missions were flown to study deep space. Their climax is the joint mission to explore Mars, called ExoMars, which has already sent a mission to Mars. Through this close examination of these European-Russian efforts, readers will appreciate an altogether new perspective on the history of space exploration, no longer defined by competition, but rather by collaboration and cooperation.
Download or read book Searching the Heavens and the Earth written by Agustin UDIAS and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jesuits established a large number of astronomical, geophysical and meteorological observatories during the 17th and 18th centuries and again during the 19th and 20th centuries throughout the world. The history of these observatories has never been published in a complete form. Many early European astronomical observatories were established in Jesuit colleges. During the 17th and 18th centuries Jesuits were the first western scientists to enter into contact with China and India. It was through them that western astronomy was first introduced in these countries. They made early astronomical observations in India and China and they directed for 150 years the Imperial Observatory of Beijing. In the 19th and 20th centuries a new set of observatories were established. Besides astronomy these now included meteorology and geophysics. Jesuits established some of the earliest observatories in Africa, South America and the Far East. Jesuit observatories constitute an often forgotten chapter of the history of these sciences.
Download or read book Quantum Mechanics Volume 3 written by Claude Cohen-Tannoudji and published by John Wiley & Sons. This book was released on 2019-12-16 with total page 790 pages. Available in PDF, EPUB and Kindle. Book excerpt: This new, third volume of Cohen-Tannoudji's groundbreaking textbook covers advanced topics of quantum mechanics such as uncorrelated and correlated identical particles, the quantum theory of the electromagnetic field, absorption, emission and scattering of photons by atoms, and quantum entanglement. Written in a didactically unrivalled manner, the textbook explains the fundamental concepts in seven chapters which are elaborated in accompanying complements that provide more detailed discussions, examples and applications. * Completing the success story: the third and final volume of the quantum mechanics textbook written by 1997 Nobel laureate Claude Cohen-Tannoudji and his colleagues Bernard Diu and Franck Laloë * As easily comprehensible as possible: all steps of the physical background and its mathematical representation are spelled out explicitly * Comprehensive: in addition to the fundamentals themselves, the books comes with a wealth of elaborately explained examples and applications Claude Cohen-Tannoudji was a researcher at the Kastler-Brossel laboratory of the Ecole Normale Supérieure in Paris where he also studied and received his PhD in 1962. In 1973 he became Professor of atomic and molecular physics at the Collège des France. His main research interests were optical pumping, quantum optics and atom-photon interactions. In 1997, Claude Cohen-Tannoudji, together with Steven Chu and William D. Phillips, was awarded the Nobel Prize in Physics for his research on laser cooling and trapping of neutral atoms. Bernard Diu was Professor at the Denis Diderot University (Paris VII). He was engaged in research at the Laboratory of Theoretical Physics and High Energy where his focus was on strong interactions physics and statistical mechanics. Franck Laloë was a researcher at the Kastler-Brossel laboratory of the Ecole Normale Supérieure in Paris. His first assignment was with the University of Paris VI before he was appointed to the CNRS, the French National Research Center. His research was focused on optical pumping, statistical mechanics of quantum gases, musical acoustics and the foundations of quantum mechanics.
Download or read book MILCOM 2005 written by Institute of Electrical and Electronics Engineers and published by . This book was released on 2005 with total page 674 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Sounds of Early Cinema written by Richard Abel and published by Indiana University Press. This book was released on 2001-10-03 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Sounds of Early Cinema is devoted exclusively to a little-known, yet absolutely crucial phenomenon: the ubiquitous presence of sound in early cinema. "Silent cinema" may rarely have been silent, but the sheer diversity of sound(s) and sound/image relations characterizing the first 20 years of moving picture exhibition can still astonish us. Whether instrumental, vocal, or mechanical, sound ranged from the improvised to the pre-arranged (as in scripts, scores, and cue sheets). The practice of mixing sounds with images differed widely, depending on the venue (the nickelodeon in Chicago versus the summer Chautauqua in rural Iowa, the music hall in London or Paris versus the newest palace cinema in New York City) as well as on the historical moment (a single venue might change radically, and many times, from 1906 to 1910). Contributors include Richard Abel, Rick Altman, Edouard Arnoldy, Mats Björkin, Stephen Bottomore, Marta Braun, Jean Châteauvert, Ian Christie, Richard Crangle, Helen Day-Mayer, John Fullerton, Jane Gaines, André Gaudreault, Tom Gunning, François Jost, Charlie Keil, Jeff Klenotic, Germain Lacasse, Neil Lerner, Patrick Loughney, David Mayer, Domi-nique Nasta, Bernard Perron, Jacques Polet, Lauren Rabinovitz, Isabelle Raynauld, Herbert Reynolds, Gregory A. Waller, and Rashit M. Yangirov.
Download or read book Ordered and Turbulent Patterns in Taylor Couette Flow written by C. David Andereck and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 351 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seldom does a physical system, particularly one as apparently simple as the flow of a Newtonian fluid between concentric rotating cylinders, retain the interest of scientists, applied mathematicians and engineers for very long. Yet, as this volume goes to press it has been nearly 70 years since G. I. Taylor's outstanding experimental and theoretical study of the linear stability of this flow was published, and a century since the first experiments were performed on rotating cylinder viscometers. Since then, the study of this system has progressed enormously, but new features of the flow patterns are still being uncovered. Interesting variations on the basic system abound. Connections with open flows are being made. More complex fluids are used in some experiments. The vigor of the research going on in this particular example of nonequilibrium systems was very apparent at the NATO Advanced Research Workshop on "Ordered and Turbulent Patterns in Taylor Couette Flow," held in Columbus, Ohio, USA May 22-24, 1991. A primary goal of this ARW was to bring together those interested in pattern formation in the classic Taylor Couette problem with those looking at variations on the basic system and with those interested in related systems, in order to better define the interesting areas for the future, the open questions, and the features common (and not common) to closed and open systems. This volume contains many of the contributions presented during the workshop.
Download or read book Government Reports Annual Index written by and published by . This book was released on 1994 with total page 1688 pages. Available in PDF, EPUB and Kindle. Book excerpt:
