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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

War of the Moon

Medkova, Bibiana 18 December 2020 (has links)
Space, in the post-World War context, was the new frontier of ‘global’ dominion. Space Race of the 1950s was a competition to signal technological capability and military strength. The objective of War of the Moon is to unpack the motivation for Moon race in 1950s. What did countries have to gain politically, economically, socially and technologically by conquering space and landing on the moon. At what cost? Who financed it, and where did the labor, land, and raw materials sourced come from. And how it was used to accomplish said landing. Space security is a massive aspect of all current space programs, but this is not a new feature, in fact, its beginnings are in the Cold War era. The second objective of this thesis and exhibition is to understand through rhetoric analysis the language of “defense” as an ‘offensive’ strategy. The artwork uses computer technologies to interrogate media and archives mimicking the state’s methods to suppress information. The work examines through archives the erasure of minority groups from cultural depositories or archives, thereby writing them out of history as the meta themes of exploration of space, and deliberate and chronicled. It is important that this work is not viewed as reactionary, but engaged in a direct dialogue: these pieces exist within the public sphere, in exhibition and projection spaces vetted by governmental, private and non-profit agencies. What is required of the work is to be subversive — to be flexible, to remain able to move freely anywhere and everywhere, and to cross barriers when necessary.
222

Pozorování zdrojů gama záření a kalibrace observatoře Cherenkov Telescope Array / The observations of gamma ray sources and calibration of the Cherenkov Telescope Array Observatory

Juryšek, Jakub January 2020 (has links)
In this thesis, we present the Monte Carlo study of two prototypes of tele- scopes for the Cherenkov Telescope Array (CTA) observatory, followed by the first data analysis partially using our reconstruction pipeline based on Random Forests. The Monte Carlo model of the SST-1M prototype is created and val- idated by comparison with data. Using the precise Monte Carlo models, we evaluate the performance of the SST-1M and LST-1 prototypes, working so-far in mono-regime as standalone telescopes, resulting in their energy and angular resolution, and the differential sensitivity. We also present an analysis of the data from the first two Crab Nebula observation campaigns conducted with the LST-1 telescope. In the last part of the thesis, we present a study of aerosol optical depth of the atmosphere above both future sites of the CTA observa- tory, retrieved from photometric measurements of Sun/Moon photometers. We focus on the photometer in-situ calibration for nocturnal measurements and introduce corrections to minimize systematic shifts between diurnal and noc- turnal measurements. Using the developed methods, we present the aerosol characterization of both CTA sites based on the photometric data. 1
223

Methods for Multisensory Detection of Light Phenomena on the Moon as a Payload Concept for a Nanosatellite Mission

Maurer, Andreas January 2020 (has links)
For 500 years transient light phenomena (TLP) have been observed on the lunar surface by ground-based observers. The actual physical reason for most of these events is today still unknown. Current plans of NASA and SpaceX to send astronauts back to the Moon and already successful deep-space CubeSat mission will allow in the future research nanosatellite missions to the cislunar space. This thesis presents a new hardware and software concept for a future payload on such a nanosatellite. The main task was to develop and implement a high-performance image processing algorithm which task is to detect short brightening flashes on the lunar surface. Based on a review of historic reported phenomena, possible explanation theories for these phenomena and currently active and planed ground- or space-based observatories possible reference scenarios were analyzed. From the presented scenarios one, the detection of brightening events was chosen and requirements for this scenario stated. Afterwards, possible detectors, processing computers and image processing algorithms were researched and compared regarding the specified requirements. This analysis of available algorithm was used to develop a new high-performance detection algorithm to detect transient brightening events on the Moon. The implementation of this algorithm running on the processor and the internal GPU of a MacMini achieved a framerate of 55 FPS by processing images with a resolution of 4.2 megapixel. Its functionality and performance was verified on the remote telescope operated by the Chair of Space Technology of the University of Würzburg. Furthermore, the developed algorithm was also successfully ported on the Nvidia Jetson Nano and its performance compared with a FPGA based image processing algorithm. The results were used to chose a FPGA as the main processing computer of the payload. This concept uses two backside illuminated CMOS image sensor connected to a single FPGA. On the FPGA the developed image processing algorithm should be implemented. Further work is required to realize the proposed concept in building the actual hardware and porting the developed algorithm onto this platform.
224

Orbital Fueling Architectures Leveraging Commercial Launch Vehicles for More Affordable Human Exploration

Tiffin, Daniel Joseph 28 January 2020 (has links)
No description available.
225

The Boy with the Aluminum Hat

Kapela, Steven J. 10 June 2014 (has links)
No description available.
226

A Movement for Authenticity: American Indian Representations in Film, 1990 to Present

Williamson, Raya 12 May 2017 (has links)
No description available.
227

The Black O'Neill: African American Portraiture in Thirst, The Dreamy Kid, Moon of the Caribbees, The Emperor Jones, The Hairy Ape, All God's Chillun Got Wings, and The Iceman Cometh

McKnight, Harry W., Jr. 10 December 2012 (has links)
No description available.
228

Europa's Lyman-Alpha Shadow on Jupiter

Ferm, Johan January 2020 (has links)
Europa is one of the most interesting satellites in the solar system in the search ofextra-terrestrial life, as it harbours an interior water ocean under its icy surface. Watervapour in Europa’s atmosphere has been previously observed, suggesting water plumeeruptions from the surface. These plumes could potentially originate from the subsurfaceocean, and as such contain ocean constituents that can be examined in orbit. Twoobservations of Europa’s far-ultraviolet shadow on Jupiter were made by the HubbleSpace Telescope in 2018 and 2019. It was observed in Lyman-α (1 216 Å), a spectral lineof hydrogen. This study investigates the imaged Lyman-α shadow in search of potentialplumes at the shadow limb. Examining the shadow instead of the moon itself is a newmethod of remotely studying the Europan atmosphere. Forward modelling is applied tocreate artificial images that are compared to the observations. Any anomalies aroundthe shadow limb are then analysed and evaluated for their statistical significance. Twonoteworthy outliers are found at the limb (one on each occasion) corresponding to H2Oline of sight column densities of 3.07×1017 cm−2 and 4.72×1016 cm−2, for the 2018 and2019 observation, respectively. They are not significant however, as they lie within threestandard deviations from the expected value (< 3σ). An upper limit on what columndensity is detectable in the data is computed, yielding 6.71×1016 cm−2 (using only 2019data due to a weak signal on the 2018 occasion). A constraint on the maximum possibleH2O column density at Europa is thus provided. The new method is shown to be usefulfor the intended purpose and could potentially be applied on other icy moons. / Europa är ett av solsystemets mest intressanta objekt i jakten på utomjordiskt liv, dådet finns ett hav av vatten under månens isiga yta. Vattenånga har tidigare observeratsi Europas atmosfär, vilket kan tyda på vattenplymer som skjuts ut från ytan i kraftigautbrott. Dessa plymer kan möjligtvis ha sitt ursprung i månens inre hav, de kandärför möjliggöra en analys av havsvattnets beståndsdelar i omloppsbana. Europasultravioletta skugga på Jupiter observerades vid två tillfällen 2018 och 2019, av HubbleSpace Telescope. Observationerna gjordes i Lyman-α (1 216 Å), en spektrallinje hos väte.Denna studie undersöker den avbildade skuggan i Lyman-α för att söka efter potentiellavattenplymer vid skuggans rand. Att undersöka skuggan istället för själva månen är en nymetod för att studera Europas atmosfär genom fjärranalys. Metoden forward modellinganvänds för att skapa artificiella bilder, som jämförs med observationerna. Eventuellaavvikelser som hittas runt skuggans rand analyseras sedan och deras statistiska signifikansutvärderas. Två anmärkningsvärda avvikelser kan hittas vid randen (en vid varjeobservationstillfälle), som motsvarar H2O-kolumndensiteter på 3.07 × 1017 cm−2 och4.72 × 1016 cm−2, för 2018-observationen respektive 2019-observationen. Densiteternaär dock inte signifikanta, då de ligger inom tre standardavvikelser från deras förväntadevärden (< 3σ). Istället beräknas en övre gräns för vilken kolumndensitet som kandetekteras i datan, vilket ger 6.71 × 1016 cm−2 (där endast 2019-data används på grundav en svag signal hos 2018-observationen). Den högsta möjliga H2O-kolumndensitetenkan således begränsas. Den nya metoden visar sig vara användbar för det tänkta syftetoch kan eventuellt appliceras på andra ismånar.
229

Navigation autonome par imagerie de terrain pour l'exploration planétaire / Autonomous vision-based terrain-relative navigation for planetary exploration

Simard Bilodeau, Vincent January 2015 (has links)
Abstract: The interest of major space agencies in the world for vision sensors in their mission designs has been increasing over the years. Indeed, cameras offer an efficient solution to address the ever-increasing requirements in performance. In addition, these sensors are multipurpose, lightweight, proven and a low-cost technology. Several researchers in vision sensing for space application currently focuse on the navigation system for autonomous pin-point planetary landing and for sample and return missions to small bodies. In fact, without a Global Positioning System (GPS) or radio beacon around celestial bodies, high-accuracy navigation around them is a complex task. Most of the navigation systems are based only on accurate initialization of the states and on the integration of the acceleration and the angular rate measurements from an Inertial Measurement Unit (IMU). This strategy can track very accurately sudden motions of short duration, but their estimate diverges in time and leads normally to high landing error. In order to improve navigation accuracy, many authors have proposed to fuse those IMU measurements with vision measurements using state estimators, such as Kalman filters. The first proposed vision-based navigation approach relies on feature tracking between sequences of images taken in real time during orbiting and/or landing operations. In that case, image features are image pixels that have a high probability of being recognized between images taken from different camera locations. By detecting and tracking these features through a sequence of images, the relative motion of the spacecraft can be determined. This technique, referred to as Terrain-Relative Relative Navigation (TRRN), relies on relatively simple, robust and well-developed image processing techniques. It allows the determination of the relative motion (velocity) of the spacecraft. Despite the fact that this technology has been demonstrated with space qualified hardware, its gain in accuracy remains limited since the spacecraft absolute position is not observable from the vision measurements. The vision-based navigation techniques currently studied consist in identifying features and in mapping them into an on-board cartographic database indexed by an absolute coordinate system, thereby providing absolute position determination. This technique, referred to as Terrain-Relative Absolute Navigation (TRAN), relies on very complex Image Processing Software (IPS) having an obvious lack of robustness. In fact, these software depend often on the spacecraft attitude and position, they are sensitive to illumination conditions (the elevation and azimuth of the Sun when the geo-referenced database is built must be similar to the ones present during mission), they are greatly influenced by the image noise and finally they hardly manage multiple varieties of terrain seen during the same mission (the spacecraft can fly over plain zone as well as mountainous regions, the images may contain old craters with noisy rims as well as young crater with clean rims and so on). At this moment, no real-time hardware-in-the-loop experiment has been conducted to demonstrate the applicability of this technology to space mission. The main objective of the current study is to develop autonomous vision-based navigation algorithms that provide absolute position and surface-relative velocity during the proximity operations of a planetary mission (orbiting phase and landing phase) using a combined approach of TRRN and TRAN technologies. The contributions of the study are: (1) reference mission definition, (2) advancements in the TRAN theory (image processing as well as state estimation) and (3) practical implementation of vision-based navigation. / Résumé: L’intérêt des principales agences spatiales envers les technologies basées sur la vision artificielle ne cesse de croître. En effet, les caméras offrent une solution efficace pour répondre aux exigences de performance, toujours plus élevées, des missions spatiales. De surcroît, ces capteurs sont multi-usages, légers, éprouvés et peu coûteux. Plusieurs chercheurs dans le domaine de la vision artificielle se concentrent actuellement sur les systèmes autonomes pour l’atterrissage de précision sur des planètes et sur les missions d’échantillonnage sur des astéroïdes. En effet, sans système de positionnement global « Global Positioning System (GPS) » ou de balises radio autour de ces corps célestes, la navigation de précision est une tâche très complexe. La plupart des systèmes de navigation sont basés seulement sur l’intégration des mesures provenant d’une centrale inertielle. Cette stratégie peut être utilisée pour suivre les mouvements du véhicule spatial seulement sur une courte durée, car les données estimées divergent rapidement. Dans le but d’améliorer la précision de la navigation, plusieurs auteurs ont proposé de fusionner les mesures provenant de la centrale inertielle avec des mesures d’images du terrain. Les premiers algorithmes de navigation utilisant l’imagerie du terrain qui ont été proposés reposent sur l’extraction et le suivi de traits caractéristiques dans une séquence d’images prises en temps réel pendant les phases d’orbite et/ou d’atterrissage de la mission. Dans ce cas, les traits caractéristiques de l’image correspondent à des pixels ayant une forte probabilité d’être reconnus entre des images prises avec différentes positions de caméra. En détectant et en suivant ces traits caractéristiques, le déplacement relatif du véhicule (la vitesse) peut être déterminé. Ces techniques, nommées navigation relative, utilisent des algorithmes de traitement d’images robustes, faciles à implémenter et bien développés. Bien que cette technologie a été éprouvée sur du matériel de qualité spatiale, le gain en précision demeure limité étant donné que la position absolue du véhicule n’est pas observable dans les mesures extraites de l’image. Les techniques de navigation basées sur la vision artificielle actuellement étudiées consistent à identifier des traits caractéristiques dans l’image pour les apparier avec ceux contenus dans une base de données géo-référencées de manière à fournir une mesure de position absolue au filtre de navigation. Cependant, cette technique, nommée navigation absolue, implique l’utilisation d’algorithmes de traitement d’images très complexes souffrant pour le moment des problèmes de robustesse. En effet, ces algorithmes dépendent souvent de la position et de l’attitude du véhicule. Ils sont très sensibles aux conditions d’illuminations (l’élévation et l’azimut du Soleil présents lorsque la base de données géo-référencée est construite doit être similaire à ceux observés pendant la mission). Ils sont grandement influencés par le bruit dans l’image et enfin ils supportent mal les multiples variétés de terrain rencontrées pendant la même mission (le véhicule peut survoler autant des zones de plaine que des régions montagneuses, les images peuvent contenir des vieux cratères avec des contours flous aussi bien que des cratères jeunes avec des contours bien définis, etc.). De plus, actuellement, aucune expérimentation en temps réel et sur du matériel de qualité spatiale n’a été réalisée pour démontrer l’applicabilité de cette technologie pour les missions spatiales. Par conséquent, l’objectif principal de ce projet de recherche est de développer un système de navigation autonome par imagerie du terrain qui fournit la position absolue et la vitesse relative au terrain d’un véhicule spatial pendant les opérations à basse altitude sur une planète. Les contributions de ce travail sont : (1) la définition d’une mission de référence, (2) l’avancement de la théorie de la navigation par imagerie du terrain (algorithmes de traitement d’images et estimation d’états) et (3) implémentation pratique de cette technologie.
230

Use of raw Martian and Lunar soils for surface-based reactor shielding

Christian, Jose L. 1963- 13 October 2014 (has links)
For several decades, the idea of flying and landing a less-than-man-rated nuclear reactor for planetary surface applications has been considered. This approach promises significant mass savings and therefore reduction in launch cost. To compensate for the lack of shielding, it has been suggested the use of in-situ materials for providing radiation protection. This would take the form of either raw dirt walls or processed soil materials into blocks or tile elements. As a first step in determining the suitability of this approach, it is necessary to understand the neutron activation characteristics of these soils. A simple assessment of these activation characteristics was conducted for both Martian and Lunar soils using ORIGEN2.2. An average composition for these soils was assumed. As a baseline material, commonly used NBS-03 concrete was compared against the soils. Preliminary results indicate that over 2.5 times more gamma-radiation production of these soils vs. concrete took place during the irradiation phase (a baseline of 2.4 x 1011 neutrons/sec-cm2 was assumed). This was due primarily to radiative capture on Na23 and Mn55 and subsequent decay of their activation products. This is does not necessarily disqualify these materials as potential shielding material since the -radiation output was only in the order of 4.2 x 108 photons/cm3-sec. Furthermore, these soils did not show any significant activity after shutdown of the neutron source (the reactor), since all activation products had very short half lives. Their performance in this area was comparable to that of NBS-03 concrete. / text

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