Global ETD Search

11	Etude photométrique des lunes glacées de Jupiter / Photometric study of Jupiter's moons Belgacem, Ines 15 November 2019 (has links) Les satellites glacés de Jupiter sont d'un grand intérêt scientifique dans la recherche d'habitabilité au sein de notre système solaire. Elles abritent probablement toutes trois des océans d'eau liquide sous leur croûte glacée. Leurs surfaces présentent différents stades d’évolution – celle de Callisto est très ancienne et entièrement recouverte de cratères, celle de Ganymede est un mélange de terrains sombres et cratérisés et de plaines claires et plus jeunes et la surface d’Europa est la plus jeune et présente des signes d’activité récente. Cette thèse porte sur la photométrie, c’est à dire l’étude de l’énergie lumineuse réfléchie par une surface, en fonction des géométries d’éclairement et d’observation. Les études photométriques permettent de déterminer l’état physique et la microtexture des surfaces (porosité, structure interne, forme des grains, rugosité, transparence…). Une bonne connaissance photométrique est également d'une importance cruciale dans la correction des jeux de données pour toute étude cartographique ou spectroscopique ainsi que pour les futures missions de cette décennie : Europa Clipper de la NASA et JUpiter ICy Moons Explorer de l’ESA.Deux types d’information sont nécessaires pour réaliser une étude photométrique : des données de réflectance et des données géométriques (conditions d’illumination et d'observation). Pour obtenir les premières, nous avons utilisé et calibré des images de missions spatiales passées - Voyager, New Horizons et Galileo. Pour obtenir les secondes, nous avons développé des outils permettant de corriger les métadonnées de ces images (ex : la position et l'orientation des sondes) afin d’obtenir des informations géométriques précises. Nous avons, d’autre part, développé un outil d’inversion pour estimer les paramètres photométriques de Hapke sur des régions d’Europa, Ganymede et Callisto sur l’ensemble du jeu de données en un seul calcul. Enfin, nous discutons des liens possibles entre les paramètres photométriques estimés, la microtexture de la surface et les processus endogènes/exogènes mis en jeu. / Jupiter's icy moons are of great interest in the search for habitability in our Solar System. They probably all harbor liquid water ocean underneath their icy crust. Their surfaces present different stages of evolution – Callisto is heavily cratered and the oldest, Ganymede shows a combination of dark cratered terrain and younger bright plains and Europa’s surface is the youngest with signs of recent and maybe current activity. This work focuses on photometry, i.e. the study of the light scattered by a surface in relation to the illumination and observation geometry. Photometric studies give us insight on the physical state and microtexture of the surface (compaction, internal structure, shape, roughness, transparency…). A good photometric knowledge is also of crucial importance in the correction of datasets for any mapping or spectroscopic study as well as for the future missions of this decade – NASA’s Europa Clipper and ESA’s JUpiter ICy moons Explorer.Two pieces of information are necessary to conduct a photometric study – reflectance data and geometric information (illumination, viewing conditions). For the former, we have used and calibrated images from past space missions – Voyager, New Horizons and Galileo. For the latter, we have developed tools to correct these images metadata (e.g. spacecraft position and orientation) to derive precise geometric information. Moreover, we have developed a Bayesian inversion tool to estimate Hapke’s photometric parameters on regions of Europa, Ganymede and Callisto. We estimate all parameters on our entire dataset at once. Finally, we discuss the possible links between the photometric parameters, the surface microtexture and endogenic/exogenic processes. Planétologie Photométrie BRDF Réflectance Surface Europe Ganymède Callisto Traitement d'images Inversion Bayésienne Technologie spatiale Navigation basée vision Planetary science Photometry BRDF Reflectance Surface Europa Ganymede Callisto Image processing Bayesian inversion Space technology Vision-based navigation
12	Juice/JDC ion measurement perturbations caused by spacecraft charging in the solar wind and Earth’s magnetosheath van Winden, Derek January 2024 (has links) In July 2031, a new chapter in the exploration of the Jovian system will begin with the arrival of the Jupiter Icy Moons Explorer (Juice) at Jupiter. Launched on April 14 2024 as part of ESA’s Cosmic Vision programme, the mission aims to study Jupiter and its icy Galilean moons Callisto, Europa, and Ganymede. Juice carries a whole suite of instruments for in-situ and remote ground observations, one of which is the Jovian plasma Dynamics and Composition analyser (JDC). As a part of the Particle Environment Package (PEP), the particle detector will measure the energy, mass, charge and arrival direction of ions and electrons in the Jovian magnetosphere. Spacecraft charging caused by interactions between the spacecraft and its surrounding plasma environment poses a significant problem for JDC because the electrostatic potential of the spacecraft accelerates/decelerates charged particles, resulting in distorted measurements, particularly for the lowest energy particles. In this report, we show the results of spacecraft charging and instrument simulations performed in the Spacecraft Plasma Interaction System (SPIS) for the solar wind and Earth’s magnetosheath—two environments that Juice will encounter at the start of the cruise phase. We found that the conductive surfaces that cover the majority of the spacecraft become positively charged as a result of a large photoelectron current in both the solar wind and magnetosheath environments. We show that these surfaces are expected to reach potentials of 9 V in the solar wind and 4 V in the magnetosheath. The four radiators on Juice that are covered with dielectric paint and shaded by the sun shield become negatively charged in both simulated environments. The radiator potentials can be as low as -40 V in the solar wind and -100 V in the magnetosheath. We also conclude that due to blocking by the spacecraft main body, the ion population cannot be sampled in the solar wind unless a spacecraft roll is performed. Furthermore, due to the high ion f low energy, spacecraft charging will not influence JDC measurements in this environment. In the magnetosheath, the ion population can be sampled by JDC, and we identified three distortion mechanisms: (1) repulsion by the main body, (2) attraction by two of the radiators, and (3) repulsion by the MAG boom. Of all the distortion modes, the one originating from a negatively charged (-67.8 V) radiator close to JDC is the strongest, affecting ions with energies above 80 eV. The least powerful but most prevalent mode is the repulsion of ions by the main body. Our results can be compared with future in-situ measurements to identify distortion mechanisms well ahead of the science phase in which the scientifically important measurements will be carried out. Juice Jupiter Icy Moons Explorer JDC Particle Environment Package PEP Jupiter Ganymede Callisto Europa solar wind magnetosheath spacecraft charging Spacecraft Plasma Interaction Software SPIS charging plasma measurement perturbations perturbation distortion particle detector Institutet för Rymdfysik IRF Dublin Institute for Advanced Studies DIAS European Space Agency ESA Fusion, Plasma and Space Physics Fusion, plasma och rymdfysik
13	Homoerotisk sensibilitet : Byggandet av homosexuell identitet genom konsthistorien / Homoerotic Sensibility : The Construction of Homosexual Identity Throughout the History of Art Varnauskas, Jacob January 2020 (has links) The question of homoerotic sensibility is, in the purpose of this thesis, a matter of visual language connected to the portrayal of male bodies. By identifying this sensibility throughout the western art canon the essay seeks to understand its origins, development and function in relation to expressions of power. With the introduction of theorists such as Alois Riegl, Laura Mulvey, Abigail Solomon-Godeau and Raewyn Connell, the aim is to deconstruct homosexual masculinity. Adapting formal analysis and parts of visual semiotics, the focus lies on the visual expression of power through the homoerotic gaze, and asks what consequences it has in forming homosexual identity. Greek antiquity is home not only to the ideals that foster western art history, but is also where we find early examples of same-sex affection being portrayed in the arts. Hence classical antiquity is so important for the homoerotic: whenever the classical language of style is popular throughout history, we are sure to find homoerotic sensibility. For reasons mentioned, the main periods analyzed are the Italian Renaissance, the French Neoclassicism and then, naturally the late 20th century onwards as this is the period of gay liberation and modern homosexual identity. By identifying classical acceptance of homosexual relations only in the form of a clear social hierarchy, we soon discover how homosexuality has appropriated the idea of binary difference within its masculinity throughout history. Accepting relationships only between erastes and eromenos, or man and ephebe, homosexuality is forced to exist only on the terms of difference of power. With classical ideals, these tendencies are recurring in the visual representation of male homosexuality, and becomes a big part of the liberation and forming of a modern identity in the late twentieth century. As a result of objectification of the male body, in combination with idealized and sexualized power, modern gay culture has in many ways embraced a destructive culture shaped by misogynist ideas of hegemonic culture, where sexual violence exists, but is not spoken of. art history homoerotic art homoerotic painting homoerotic photography homoerotic gaze male gaze power relations antiquity identity queer theory masculinity gay culture sexuality homosexuality male representation construction body bodies visual semiotics gender gender studies Renaissance Neoclassicism Postmodernism Michelangelo di Buonarotti Ganymede Wolfgang Tillmans Paul Cadmus Tom of Finland Jacques-Louis David Merry-Joseph Blondel Michael Leonard konsthistoria konstvetenskap homoerotisk konst homoerotiskt måleri homoerotiskt fotografi homoerotik homoerotisk blick manlig blick maktförhållanden antiken identitet queerteori manlighetsforskning maskulinitet maskulinitetsteori gay kultur bög kultur sexualitet homosexualitet manlig representation konstruktion konstruktivism kropp kroppar visuell semiotik semiotik genus kön genusvetenskap renässans nyklassicism postmodernism Humanities and the Arts Humaniora och konst Art History Konstvetenskap

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