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The study of small bodies in our solar system is fundamental for understanding its youth and evolution. These small "primitive" bodies are "undifferentiated" (they did not undergo phase density-separation, irreversibly altering their mineralogy). They have evolved very little since their birth, spurring a composition relatively close to that of the primordial protoplanetary disk. However, other processes, such as thermal alteration, aqueous alteration, shocks, or space-weathering can affect these bodies' surfaces. This is an issue, since remote-sensed data acquired while studying these bodies target these very surfaces. If these surfaces have been altered, they can induce a certain bias in the study of the composition of these small bodies. Therefore, it is paramount to understand the processes affecting the surface of primitive asteroids to correctly assess their composition.There are several ways to study the surface of primitive asteroids, such as remotely, from the Earth or from a satellite orbiting the body of interest, by acquiring spectroscopic data (gaining access to surface chemical and mineralogical composition). It is also possible to study these bodies in a laboratory environment, by working on analogous materials such as certain classes of "primitive" meteorites (carbonaceous chondrites), on terrestrial analogues (simpler to study than meteorites, but less closely related to extraterrestrial materials), or directly on extraterrestrial materials brought back by sample return missions.In this work, we replicate in a laboratory environment the effects of space weathering (SpWe) on the surface of primitive asteroids. More specifically, we focus on the effects of solar wind, the dominant SpWe process on "young" surfaces of the solar system. We have chosen three terrestrial minerals analogous to a "primitive" surface - three hydrated minerals (two serpentines and one saponite) - of which we have produced several pellets which have been bombarded using He and Ar ions, to investigate the effects of two different solar wind. In doing so, we made analogous materials of weathered primitive surface matter.These analogues were then characterized by infrared spectroscopy, from the visible to the far-infrared range, to study chemical changes prompted by ion bombardment. This was done by investigating how certain spectroscopic features - characteristic of hydrated silicates - changed upon ion-bombardment. We detected several effects, such as darkening in the visible range, visible slope reddening and bluing as well as a systematic shift towards longer wavelength affecting the position of several spectroscopic features.This spectroscopic characterization was followed by a study at smaller scale, using electron microscopy. We first characterized the surface of our weathered analogues using scanning electron microscopy, and then investigated the morphological and physicochemical changes taking place in the bombarded layer, at a nano-meter scale, using transmission electron microscopy. Strong vesiculation effects of various kinds were identified in the ion-bombarded amorphized layers, as well as textural changes and some elemental concentration evolutions (such as the loss of oxygen in the utmost top surfaces, preferential amorphization of magnesium, etc.).The coupling between these two techniques, IR spectroscopy and electron microscopy, acting at different scales, has allowed for a better understanding of SpWe effects on primitive bodies, and will be able to support current and future studies of primitive bodies, whether they are carried-out remotely or in a laboratory environment on returned samples.; L'étude des petits corps du système solaire est fondamentale pour la compréhension de sa jeunesse et de son évolution. Ces petits corps « primitifs » seraient « non-différenciés » (pas d'entrée en fusion et séparation des phases altérant la minéralogie). Ils n'auraient donc que très peu évolué depuis leur naissance, avec une composition étroitement liée à celle du disque proto-planétaire originel. Pourtant, d'autres processus, comme l'altération thermique, l'altération aqueuse, les chocs ou l'altération spatiale peuvent venir altérer la surface d'un corps primitif. Ceci est problématique, car les mesures acquises à distance de ces corps ont comme cible précisément leur surface. Si celle-ci est altérée, elle peut biaiser l'étude de la composition de ces petits corps. Il est donc important de comprendre les processus affectant la surface des astéroïdes primitifs, afin de pouvoir correctement interpréter leur composition.Il y a plusieurs façons d'étudier la surface d'astéroïdes primitifs, tel que à distance, depuis la Terre ou un satellite orbitant le corps d'intérêt, en acquérant des données de spectroscopie (composition chimique et minéralogique de surface). Il est aussi possible d'étudier ces corps en laboratoire, en travaillant sur des matériaux analogues comme certaines classes de météorites « primitives » (les chondrites carbonées), sur des analogues terrestres (plus simples à étudier que les météorites, mais moins étroitement liés à la matière extraterrestre), ou enfin sur de la matière extraterrestre rapportée par les missions de retour d'échantillons.Dans cette étude, nous nous sommes proposé d'étudier en laboratoire les effets de l'altération spatiale sur les surfaces d'astéroïdes primitifs. Plus précisément, cette étude est focalisée sur les effets du vent solaire, le processus dominant d'altération spatiale sur les surfaces « jeunes » du système solaire. Nous avons choisi trois minéraux terrestres analogues à une surface « primitive » - à savoir, trois minéraux hydratés (deux serpentines et une saponite) - dont nous avons produit des pastilles que nous avons bombardé avec des ions He et Ar, afin de simuler les effets de deux contributions différentes du vent solaire. Nous avons donc produit donc des analogues de surface primitive ayant subi de l'altération spatiale.Ces analogues ont ensuite été caractérisés par spectroscopie infrarouge, du visible jusqu'à l'Infrarouge lointain, afin d'étudier l'évolution chimique après bombardement ionique de nos échantillons, en suivant les changements induit par le bombardement sur des bandes spectroscopiques caractéristiques des minéraux hydratés dans l'IR, ainsi que sur l'évolution du continuum dans le visible. Nous avons détecté plusieurs effets, tels que l'assombrissement des spectres visible, rougissement et bleuissement des pentes spectrales selon l'échantillon ainsi qu'un déplacement systématique vers les grandes longueurs d'ondes de plusieurs bandes spectrales.Cette caractérisation spectroscopique a été suivie par une étude à plus petite échelle par microscopie électronique, dédiée à caractériser la surface de nos analogues altérés par microscopie électronique à balayage, et ensuite à étudier à l'échelle nanométrique les changements morphologiques et physico-chimiques ayant lieu dans la couche bombardée, par microscopie électronique à transmission. De forts effets de bullages de différents types ont été identifiés dans la couche amorphisée par bombardement ionique, ainsi que des changements de texture et certaines évolutions élémentaires (perte d'oxygène en surface, amorphisation préférentielle du magnésium, etc.).Le couplage entre ces deux techniques, spectroscopie IR et microscopie électronique, agissant à différentes échelles, a permis une meilleure compréhension des effets d'altérations spatiale sur les corps primitifs, et pourra prêter support à l'étude de ce type de surface, qu'elle soit menée à distance ou en laboratoire sur des matériaux récoltés.

[eng] This dissertation is devoted to the analysis of the motion of small bodies, like asteroids, in the neighbourhood of the Earth-Moon system from a celestial mechanics approach. This is an extensive area of research where probably, the most extended simplified mathematical model is the well-known autonomous Hamiltonian system the Restricted Three-Body Problem (RTBP). Many modifications to this model have been proposed, looking for a more accurate description of the system. One of the simplest ways of introducing additional physical effects is through time-periodic perturbations, such that such that the new non-autonomous system is close to the autonomous one, and it has many periodic or quasi-periodic solutions. If these solutions are hyperbolic, they have stable/unstable invariant manifolds, such that stable manifolds approach the quasi-periodic solutions forward in time, meanwhile unstable manifolds do it backward in time, constituting the skeleton for the dynamical transport phenomena we are interested in. Notice that one dimension can be reduced by defining a suitable temporal Poincar´e map. Therefore, our aim is to compute the quasi-periodic solutions and their manifolds in this map. Most of the effort of this dissertation is addressed to the Bicircular Problem (BCP), in which the Earth and Moon are treated as the primaries in the RTBP and the gravitational field of the Sun is introduced as a time-periodic forcing of the RTBP. In particular, we have extensively analysed the horizontal family of two dimensional quasi-periodic solutions in the neighbourhood of the collinear unstable equilibrium point L3. We found that diverse trajectories connecting the Earth, the Moon and the outside Earth-Moon system are governed by L3 dynamics. Big attention is paid to the trajectories coming from the Moon towards the Earth, since they may give an insight of the travel that lunar meteorites perform before landing in our planet. These results have been translated and compared with those of a realistic model based on JPL (Jet Propulsion Laboratory) ephemeris, showing a good agreement between the results obtained. We also have proposed and carried out a strategy for capturing a Near Earth Asteroid (NEA) using the stable invariant manifolds of the horizontal family of quasi-periodic orbits around L3 in the BCP. To this aim the high order parametrization of the stable/unstable invariant manifolds is introduced, for which computation we have employed the jet transport technique. Finally, the strategy is applied to the NEA 2006 RH120. The contributions to the BCP presented in this dissertation include two other applications. The first one is devoted to the study of the unstable behaviour near the triangular points, meanwhile the second is devoted to a family of stable invariant curves around the Moon that are close to a resonance, promoting the appearance of chaotic motion. The last part of the dissertation is focused on the effective computation of the high or- der parametrization of the stable and unstable invariant manifolds associated with reducible invariant tori of any high dimension. To this aim, we resort on the reducible system, that offers a high degree of parallelization of the computations. Besides, we explain how to com- bine the presented methods with multiple shooting techniques to accurately compute highly unstable invariant objects. Finally, we apply the developed algorithms to compute the high order parametrization of the manifolds associated to L1 and L2 in an Earth-Moon system that includes five time-periodic forcings regarded to four physical features of the system, besides the solar gravitational field., [spa] Esta tesis analiza el movimiento de pequeños cuerpos, como asteroides, en el sistema Tierra­ Luna desde el marco de la mecánica celeste. El modelo que hemos empleado en mayor profundidad es el Problema Bicircular (PBC), el cual se puede entender como una perturbación periódica en el tiempo del conocido Problema Restringido de Tres Cuerpos (PRTC), dado que en el PBC se incluye el campo gravitatorio de un tercer cuerpo masivo que rota en movimiento circular alrededor de la configuración del PRTC. El cuerpo que causa la perturbación es para nosotros el Sol de tal forma que los objetos invariantes del PRTC adquieren una dimensión angular debida a la frecuencia del movimiento relativo entre el Sol y el baricentro Tierra-Luna. En el marco del PBC hemos analizado los fenómenos de transporte gobernados por la familia horizontal de soluciones cuasi-periódicas dos dimensionales (toros 2D) alrededor punto inestable colinear L3. Estas soluciones tienen asociadas variedades invariantes estables e inestables que constituyen el esqueleto de los fenómenos que queremos estudiar. Las trayectorias encontradas conectan la Tierra y la Luna y también el exterior/interior del sistema Tierra-Luna. Hemos prestado especial atención a las trayectorias que van de la Luna a la Tierra ya que podrían explicar el viaje que realizan los meteoritos lunares encontrados en nuestro planeta. Estos resultados han sido testeados en un modelo más realista basado en las efemérides del JPL (Jet Propulsion Laboratory). Otra de las aplicaciones propuestas es la de capturar un asteroide cercano a la Tierra usando la parametrización a orden alto de las variedades invariantes asociadas a los toros 2D alrededor de L3. La parte final trata del desarrollo de algoritmos para el cálculo preciso de la parametrización a orden alto de variedades invariantes estables/inestables asociadas a toros reducibles de cualquier dimensión alta. Además, se explica cómo combinar dichos algoritmos con métodos de tiro múltiple para aquellos objetos invariantes que sean muy inestables. Finalmente, aplicamos la metodología al cálculo de las variedades asociadas a L1 y L2 de un sistema Tierra-Luna que incluye cinco perturbaciones periódicas en el tiempo.

This thesis focuses on particle size segregation in rubble-pile asteroids, mostly by using numerical methods, but also with an experimental exploration. It is motivated by the fact that some asteroids are not monolithic, but instead consist of a assembly of rocks held together by gravitation, like for instance asteroid Itokawa. One notices an accumulation of big boulders at the surface, with a heterogeneous distribution. Given the mechanical environment of asteroids, size sorting processes are good candidates to explain these patterns.The first part of the numerical work deals with a simplified problem : simulating 2D circular asteroids undergoing isotropic and periodic expansions. In this case, we observe a radial segregation and we quantify its typical speed and strength, highlighting the strong role played by friction and rotation. We also observe and study an angular segregation, with the big grains gathering into lobes at the surface, like on Itokawa.Then, we modified the agregate's topology, which led to observing the analogous of radial and angular segregations. This enabled us to quantify the inter-lobes distance. We also studied the segregation process when the asteroid undergoes collisions: the impact velocity and the grains elasticity thus play an important role. Furthermore, we extended our numerical study to the case of 3D spherical asteroids, and observed very interesting dynamics linking radial and angular segregations with the formation of opposed lobes of big grains. This is very significant considering the surface of Itokawa.Finally, we built a simple experiment dedicated to the study of granular segregation in a central force field., Cette thèse porte sur la ségrégation granulaire au sein des astéroïdes lâchement agglomérés, avec une approche surtout numérique mais aussi expérimentale. Ce travail est motivé par l’observation d’astéroïdes non monolithiques, mais formés de différents blocs maintenus ensemble par la gravitation, comme par exemple l’astéroïde Itokawa. On y constate la présence de nombreux gros rochers à la surface, et une inhomogénéité de leur répartition. Au vu des sollicitations mécaniques subies par les astéroïdes, un processus de ségrégation granulaire peut expliquer ces observations. Un premier travail numérique porte sur un problème modèle : un astéroïde bidimensionnel, circulaire, soumis à des expansions isotropes et périodiques. Dans ce cadre, nous observons une ségrégation radiale, dont nous quantifions la netteté et la rapidité, avec un rôle important joué par le frottement solide et la rotation des grains. De plus, nous observons et étudions une ségrégation angulaire : les gros grains forment des lobes à la surface, rappelant le cas d’Itokawa. Nous avons ensuite modifié la topologie de l’agrégat, retrouvant alors des analogues à la ségrégation radiale et à la ségrégation angulaire. Nous mettons ainsi en évidence une longueur d’onde typique quantifiant la distance entre lobes. Nous avons également étudié la ségrégation sous collisions, la vitesse d’impact et l’élasticité des contacts jouant alors un rôle important. Enfin, l’étude a été étendue au cas d’astéroïdes tridimensionnels sous expansions isotropes, montrant une dynamique particulière liant fortement ségrégation radiale et angulaire, et des lobes antipodaux de gros grains. Cela est très significatif vis-à-vis du cas d’Itokawa. Enfin, nous avons construit une expérience permettant d’étudier la ségrégation en champ gravitationnel central.

Submitted by Abreuçon Atanasio Alves (abreucon.alves@unesp.br) on 2021-10-06T12:26:59Z No. of bitstreams: 1 Dissertacao_AAA.pdf: 2523415 bytes, checksum: 2be235155c4b44efd68588a9841d9de3 (MD5) Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2021-10-16T03:38:08Z (GMT) No. of bitstreams: 1 alves_aa_me_guara.pdf: 3793498 bytes, checksum: 143fe73627bc6bf28c187e2162c71845 (MD5) Made available in DSpace on 2021-10-16T03:38:09Z (GMT). No. of bitstreams: 1 alves_aa_me_guara.pdf: 3793498 bytes, checksum: 143fe73627bc6bf28c187e2162c71845 (MD5) Previous issue date: 2021-07-09 Ceres é um planeta anão que orbita o Sol no Cinturão de Asteroides. A presença de água em grande quantidade, amônia, alguns sais e propriedades únicas comparadas com outros asteroides do Cinturão Principal sugere que Ceres não foi formado in situ. Um provável cenário é que ele foi formado na região externa do Sistema Solar e implantado na órbita atual durante a evolução e formação dinâmica do Sistema Solar. Neste trabalho, nós utilizamos simulações numéricas do Sistema Solar externo primordial para investigar possíveis mecanismos dinâmicos responsáveis por colocar planetesimais do tamanho de Ceres no Cinturão de Asteroides. Inicialmente simulamos o esculpimento dinâmico do disco de planetesimais primordial, durante a formação de Urano e Netuno proveniente de colisões gigantescas entre embriões planetários durante a fase em que o Sistema Solar era envolvido por um disco de gás. Em seguida, nós calculamos a fração de planetesimais do tipo Ceres que foram capturados na região interna do Sistema Solar (a

The discovery of lunar ice in 1998 opened a whole variety of new perspectives for in-situ resource utilization of water on the Moon. However, more recent studies suggest that the amount of lunar ice is scarce. On the other hand, almost every single space agency and a substantial number of private initiatives advocate for a human return to our natural satellite and establishement of a permanent outpost. In this work, a feasibility study of using water from an asteroidal source in lunar orbit will be carried out, including the astrodynamics of asteroid capture and orbital insertion, exploitation approach and a techno-economic analysis of asteroidal water utilization for lunar development. First, selecting and analysing the best candidate asteroid for the mission (asteroid 2010DL). Subsequently, all the technical parameters of the mission will be analysed in order to conclude that due to the current propulsion systems, the impulse times required to accelerate or decelerate the mass of asteroid 2010DL are much longer than the natural flight time that the manoeuvres would have, so it is concluded that with the current propul-sion systems it is not possible to decelerate an asteroid of 19 metres in diameter of type C fast enough on its entry into the Earth’s capture orbit, It then proposes a solution that satisfies both the technical and economic constraints, which is to extract the water directly in the asteroid’s own orbit and send tanks of 9500 litres of water directly from the perigee and apogee of the asteroid’s orbit to a moon distant retrograde orbit.

Imaging resolution is severely reduced in astronomy due to the atmospheric turbulence. The resulting Point Spread Function (PSF) is large and is equivalent to the one of a diffraction limited telescope of a dozen of centimetres in the visible. Adaptive Optics (AO) is a real time compensation of the turbulence significantly increasing the resolution. However AO correction is only partial, damaging especially the shorter wavelengths. The deconvolution post-processing technique restores the information contained in the image although attenuated by the turbulence effect.This deconvolution requires the input of the PSF, often unknown or poorly known in ground-based astronomy. The current work focuses on i) writing and validating a PSF model dedicated to AO observations, and ii) the use of this PSF model for deconvolution purposes. The PSF model developed here includes physical parameters such as the Fried parameter or the AO residual phase variance. Thanks to this physical origin, this PSF model precisely fits the AO PSF shape and its parameters may be constrained by telemetry. Robustness and versatility of the model are proven on the SPHERE/Zimpol imager and the MUSE spectro-imager from VLT. Then the model is used for deconvolution of astronomical images. We show that the joint deconvolution, which estimates simultaneously the object and the PSF, is degenerated. Instead we use the marginal approach : the image is used to estimate first the PSF, the object is estimated only in a second step. These deconvolution techniques using parametric PSF are applied on asteroid images from the ESO Large Program., La résolution des images astronomiques est sévèrement dégradée par la turbulence atmosphérique. La réponse impulsionnelle (Point Spread Function, PSF) du système d’imagerie, télescope et atmosphère, est étendue et ne permet pas d’atteindre la limite de diffraction d’un télescope de quelques dizaines de centimètres dans le visible. L’optique adaptative (OA) est une correction en temps réel de la turbulence atmosphérique qui augmente considérablement la résolution du système. Cependant la correction d’OA est seulement partielle, affectant particulièrement la résolution d’imagerie aux courtes longueurs d’ondes. La déconvolution est une technique de traitement a posteriori qui permet de restaurer l’information contenue dans l’image mais qui a été atténuée par la turbulence. Cette déconvolution nécessite l’utilisation de la PSF du système, souvent inconnue ou incorrectement estimée. Le travail présenté ici montre l’intérêt d’utiliser un modèle paramétrique de PSF en traitement d’image. Les deux grands axes de ce travail sont alors i) la création et validation d’un modèle de PSF adapté à la correction OA et ii) l’utilisation de ce modèle de PSF pour la déconvolution. Le modèle proposé ici inclut des paramètres physiques, dont le paramètre de Fried qui indique la force de la turbulence ou la variance de phase corrigée par OA. Grâce à son origine physique, ce modèle de PSF corrigée par OA est précis sur la forme de la PSF et ses paramètres peuvent être déterminés par des données de la boucle OA. La robustesse et adaptabilité du modèle sont validées notamment sur l’imageur SPHERE/Zimpol et sur le spectro-imageur MUSE du VLT. Ensuite le modèle est utilisé en déconvolution d’images astronomiques. Nous montrons que la déconvolution jointe qui estime à la fois la PSF et l’objet est dégénérée. A la place nous appliquons une technique dite de marginalisation: l’image est utilisée pour estimer dans un premier temps uniquement la PSF. Nous démontrons la consistance de cette approche. Puis, dans un second temps, la PSF estimée est injectée dans un algorithme de déconvolution classique (non myope, à PSF fixée). Les techniques de déconvolution avec PSF paramétriques sont appliquées à l’ESO Large Program d’observation d’astéroïdes de la ceinture principale.

Reflectance spectroscopy is one of the major techniques used to retrieve information on physical and mineralogical configuration of the surface of planetary bodies. However, the reflectance of a surface strongly depends on parameters unrelated to its surface, such as the temperature or the illumination and observation configuration. The new spectro-gonio radiometer at IPAG, SHADOWS, has been specially designed to conduct bidirectional reflectance spectroscopy on dark and small surfaces, such as meteorites. This goniometeralso owns two environmental cells, MIRAGE and IceBERG, allowing the study on thesamples under similar temperature and pressure conditions as the Solar System small bodies. The analysis of the hydration signatures on meteoritic spectra under asteroidal condition showed the alteration of the mineralogy by the high temperature. A new deconvolution model has been used to separate and independently analyze the components of the 3-µm band. Comparison between laboratory measurements and telescopic observations of asteroids highlighted the link between this spectral signature and the aqueous and thermal alteration history of the surface. A serie of bidirectional reflectance spectroscopyon various surfaces showed that the reflectace strongly depends on the geometrical configuration of the measurement. These results have been then applied to a simulated asteroid to show the effect of the shape of the body on its integrated spectrum.; La spectroscopie en réflectance est l’une des techniques majeures permettant d’obtenir des informations physiques et minéralogiques sur la surfaces des corps planétaires. Cependant, la réflectance d’un corps dépend fortement de paramètres extérieurs à sa surface, tels que sa température ou encore la configuration de l’éclairement et de l’observation. Le nouveau spectro-gonio radiomètre de l’IPAG, SHADOWS, a été spécialement conçu pour réaliser des mesures de réflectance bidirectionnelle de surfaces sombres et de petite taille, telles que les météorites. Ce goniomètre compte également deux cellules environnementales, MIRAGE et IceBERG, permettant de placer les échantillons étudiés dans des conditions de température et pression similaires aux petis corps du Système Solaire. L’analyse des signatures d’hydratation détectées sur des spectres de météorites en conditions astéroïdales a permis de mettre en évidence l’altération de la minéralogie due à la haute température. Un nouveau modèle de déconvolution a été utilisé pour séparer et analyse de manière indépendante les composantes de la bande à 3-µm. La comparaison entre les mesures effectuéesen laboratoire et les observations d’astéroïdes ont mis en évidence un lien entre cette signature spectrale et l’histoire d’altération aqueuse et thermique de la surface. La dépendance de la réflectance avec la géométrie de la mesure a été montré par une série d’analyse en réflectance bidirectionnelle de différentes surfaces. Ces résultats ont ensuite été appliqués sur des simulations d’astéroïde, pour montrer l’effet de la forme du corps sur son spectre intégré.

Conselho Nacional do Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná Objetos Transnetunianos (TNOs) são corpos menores do Sistema Solar; podem ser vistos como objetos sob a ação de auto-gravidade, forças relacionadas a rotação e forças de maré, classicamente considerados como de comportamento fluido e, portanto, assumindo formas de equilíbrio fluidas. Contudo, eles são compostos por materiais geológicos, que raramente comportam-se como fluidos; logo, o uso de critérios geológicos para analisar as formas assumidas por esses objetos quando em equilíbrio, i.e. formas de equilíbrio, é necessário, resultando em uma melhor compreensão de suas propriedades. O presente trabalho propõe a utilização do método descrito por Holsapple (2004) para a avaliação do estado de equilíbrio de corpos menores. Foram estudados os TNOs Haumea, Quaoar e 2002 VS2, os centauros Chariklo e 2002 GZ32, e os asteróides Ceres, Vesta e Lutetia. Suas formas (determinadas com alta precisão a partir de ocultações estelares ou dados coletados por sondas espaciais), período de rotação e densidade (quando disponível) foram usados para determinar: i) se o objeto está em equilíbrio; ii) se apresenta comportamento fluido ou se tem algum tipo de resistência a deformação; e iii) as implicações geológicas dessas conclusões. No caso da ausência de valores de massa, como é o caso para 2003 VS2, Chariklo e 2002 GZ32, o método foi usado para se obter uma estimativa da densidade, partindo do pressuposto de que apresentam comportamento fluido e estão em equilíbrio. Concluiu-se que todos os objetos avaliados estão em equilíbrio, porém com formas usualmente diferentes do caso fluido (i.e. elipsóides de Maclaurin e Jacobi). Foi demonstrado que o comportamento dos materiais é um indicativo da possível composição e estruturação interna de um objeto, o que está diretamente relacionado aos processos geológicos que atuaram e atuam neles; isso permite entender, ao menos em termos gerais, sua história e evolução geológicas a partir do uso de modelos e de análogos. Além disso, TNOs e outros mundos gelados contém ambientes únicos, muito diferentes de tudo visto na Terra; eles podem ser vistos como grandes laboratórios em escala real, possivelmente contendo um grande número de processos geológicos únicos à eles e capazes de mudar alguns dos paradigmas atuais nesse campo da ciência. Transneptunian Objects (TNOs) are small bodies of the Solar System; they can be seen as spinning bodies under the influence of self-gravity, spin-related forces and tidal forces, classically considered to have fluid behaviour and, therefore, assume fluid equilibrium shapes. However, they are composed by geological materials that rarely behaves as fluids; thus, the use of geological criteria to analyse the shapes assumed by these objects when in equilibrium, i.e. their equilibrium shape, is required, resulting in more accurate understanding of their nature. This work proposes using the method described by Holsapple (2004) to evaluate the equilibrium state of small bodies. The TNOs Haumea, Quaoar and 2003 VS2, the centaurs Chariklo and 2002 GZ32, and the asteroids Ceres, Vesta and Lutetia were studied. Their shape (determined with high accuracy through the use of stellar occultations and data collected by space probes), rotation period and density (whenever available) were used to determine: i) if the object is in equilibrium; ii) if it presents fluid behaviour or if it has some type of internal resistance to deformation; and iii) the geological implications of this. In the absence of mass values, as is the case for 2003 VS2, Chariklo and 2002 GZ23, the method was used to infer the object’s density, under the assumptions that it presents fluid behaviour and is in equilibrium. All objects were found to be in equilibrium, but with shapes usually different than the fluid case (i.e. Maclaurin and Jacobi ellipsoids). It was shown that the material’s behaviour is an indicative of the possible internal composition and structure of an object, what is closely related to geological processes that took and are taking place on it; it allows the understanding, at least in general terms, of their geological history and evolution through the use of models and analogs. In addition to that, TNOs and other icy worlds present unique environments, very different than anything on Earth; they can be seen as huge real-life laboratories, possibly containing a vast number of geological processes unique to them and capable of changing some of the current paradigms of this field of science.

Fast development of CubeSat technology now enables the first interplanetary missions. The potential application of CubeSats to flyby near-Earth asteroids is explored in this paper in consideration of CubeSats' limited propulsive capabilities and systems constraints. Low-energy asteroid flyby trajectories are designed assuming a CubeSat is initially parked around to the Sun-Earth Lagrange points. High-impulse and low-thrust trajectories with realistic thrusting models are computed first in the Circular Restricted Three-Body Problem (CR3BP), and then in a high-fidelity ephemeris model. Analysis in the ephemeris model is used to confirm that trajectories computed in the CR3BP model also exist in a more realistic dynamical model, and to verify the validity of the results obtained in CR3BP analysis. A catalogue of asteroid flyby opportunities between years 2019 and 2030 is provided, with 80 m/s of available ΔV and departure from halo orbits around the first and second Sun-Earth Lagrange points (of similar size to those typically used by scientific missions). Results show that the CR3BP model can serve as an effective tool to identify reachable asteroids and can provide an initial estimation of the ΔV cost in the ephemeris model (with ±15 m/s accuracy). An impulsive maneuver model can also provide an accurate estimation of the ΔV requirement for a CubeSat equipped with a high-impulse thruster (with 4 m/s accuracy), even if its thrust magnitude is small and requires duty cycling; low-thrust ΔV requirements, however, may differ significantly from the impulsive results (±15 m/s)., Funding was provided by Cranfield University’s European Partnership Programme (2016–2017, United Kingdom).

Reflectance spectroscopy is one of the major techniques used to retrieve information on physical and mineralogical configuration of the surface of planetary bodies. However, the reflectance of a surface strongly depends on parameters unrelated to its surface, such as the temperature or the illumination and observation configuration. The new spectro-gonio radiometer at IPAG, SHADOWS, has been specially designed to conduct bidirectional reflectance spectroscopy on dark and small surfaces, such as meteorites. This goniometeralso owns two environmental cells, MIRAGE and IceBERG, allowing the study on thesamples under similar temperature and pressure conditions as the Solar System small bodies. The analysis of the hydration signatures on meteoritic spectra under asteroidal condition showed the alteration of the mineralogy by the high temperature. A new deconvolution model has been used to separate and independently analyze the components of the 3-µm band. Comparison between laboratory measurements and telescopic observations of asteroids highlighted the link between this spectral signature and the aqueous and thermal alteration history of the surface. A serie of bidirectional reflectance spectroscopyon various surfaces showed that the reflectace strongly depends on the geometrical configuration of the measurement. These results have been then applied to a simulated asteroid to show the effect of the shape of the body on its integrated spectrum., La spectroscopie en réflectance est l’une des techniques majeures permettant d’obtenir des informations physiques et minéralogiques sur la surfaces des corps planétaires. Cependant, la réflectance d’un corps dépend fortement de paramètres extérieurs à sa surface, tels que sa température ou encore la configuration de l’éclairement et de l’observation. Le nouveau spectro-gonio radiomètre de l’IPAG, SHADOWS, a été spécialement conçu pour réaliser des mesures de réflectance bidirectionnelle de surfaces sombres et de petite taille, telles que les météorites. Ce goniomètre compte également deux cellules environnementales, MIRAGE et IceBERG, permettant de placer les échantillons étudiés dans des conditions de température et pression similaires aux petis corps du Système Solaire. L’analyse des signatures d’hydratation détectées sur des spectres de météorites en conditions astéroïdales a permis de mettre en évidence l’altération de la minéralogie due à la haute température. Un nouveau modèle de déconvolution a été utilisé pour séparer et analyse de manière indépendante les composantes de la bande à 3-µm. La comparaison entre les mesures effectuéesen laboratoire et les observations d’astéroïdes ont mis en évidence un lien entre cette signature spectrale et l’histoire d’altération aqueuse et thermique de la surface. La dépendance de la réflectance avec la géométrie de la mesure a été montré par une série d’analyse en réflectance bidirectionnelle de différentes surfaces. Ces résultats ont ensuite été appliqués sur des simulations d’astéroïde, pour montrer l’effet de la forme du corps sur son spectre intégré.

Per tal de comprendre el Sistema Solar en la seva forma actual i la formació dels planetes, els cossos menors juguen un paper clau. La composició d’asteroides i cometes ens proporciona claus sobre el naixement del Sistema Solar i la seva evolució. Els petits cossos no diferenciats contenen els primers materials sòlids del Sistema Solar, formats arran de l’agregació i la fusió del pols primordial. A partir d’aquests primers blocs constitutius es formaren cóssos majors com ara asteroides, cometes i planetes. Els cossos rocosos amb un tamany major a pocs centenars de quilòmetres de diàmetre experimentaren segregació química degut a la diferenciació, però els menors irradiaren la calor interior i mai es van fondre. Els cossos no diferenciats han preservat els materials pristins que formaven el disc protoplanetari. Aquests materials preservats conformen els meteorits no diferenciats. Els meteorits procedint d’aquests objectes, coneguts com a condrites, són mostres dels materials formats al disc protoplanetari al voltant del Sol fa uns 4.600 milions d’anys. Entre aquests, les condrites carbonàcies són les úniques mostres disponibles que representen asteroides carbonacis que són importants per tal de comprendre les seves propietats físiques i per comparar amb les retornades per les missions Hayabusa 2 i OSIRIS-Rex. Aquesta tesi es centra en la composició química, mineralogía i propietats físico-químiques dels cossos menors del Sistema Solar mitjançant mesures al laboratori dels seus meteorits. Diverses tècniques aquí descrites permeten l’estudi de les propietats de les condrites i, d’aquesta manera, obtenir claus sobre les complexes històrias acrecionàries dels seus cossos progenitors. Els canvis mineralògics associats al metamorfisme tèrmic, l’alteració aquosa o als efectes de xoc a condrites són descrits en el context d’indagar en la natura dels seus asteroides pares. A més, s’apliquen tècniques espectroscòpiques com a mètode adient per tal d’associar els meteorits als seus asteroides específics, tot i que una associació inequívoca requerirà completar missiones de retorn de mostres. A la primera part d’aquest treball es comparen els espectres de reflexió de dos grups de condrites carbonàcies químicamente relacionades: CV i CK. Les propietats reflectives d’aquests dos grups de condrites són comparades amb la classe espectral Cg d’asteroides. Donat que els asteroides han estat exposats a impactes des de la seva formació, les seves superficies són cobertes per petites partícules, roques i blocs majors. La missió Hayabusa de JAXA va recolectar partícules del regòlit de l’asteroide 25143 Itokawa. Els estudis al laboratori d’aquestes partícules proporcionen una oportunitat científica donat que les seves propietats físiques poden ser comparades amb aquestes de les condrites que poden ser doncs considerades bons exemples dels materials constitutius dels asteroides potencialment perillosos (PHAs). A la segona part de la tesi es presenten els resultats de l’estudi de les propietats mecàniques de tres d’aquestes partícules fent servir una tècnica acurada anomenada nanoindentació. Finalment també s’estudien les propietats de cossos foscos associats amb cometes evolucionats. En aquest sentit el cometa 2P/Encke és un dels majors objectes de l’anomenat complex de les Tàurides. El seu comportament espectral fa que sigui similar a les condrites carbonàcies prístines però es desconeixia la seva natura real. A aquest treball s’ha trobat un bon ajust espectral entre el cometa i dues condrites carbonàcies sense agrupar, tot permetent fer-nos una idea sobre la composició heterogènia de la superficie d’un cometa de periode curt. Para comprender el Sistema Solar en su forma actual y la formación de los planetas, los cuerpos pequeños juegan un papel clave. La composición de asteroides y cometas nos proporciona claves sobre el nacimiento del sistema solar y su evolución. Los pequeños cuerpos no diferenciados contienen los primeros materiales sólidos del Sistema Solar, formados a partir de la agregación y el fundido del polvo primordial. A partir de estos primeros bloques constitutivos se formaron cuerpos mayores como los asteroides, cometas y planetas. Los cuerpos rocosos con un tamaño mayor a pocos cientos de kilómetros de diámetro experimentaron segregación química debido a la diferenciación, pero los menores irradiaron el calor interior y nunca se fundieron. Los cuerpos no diferenciados han preservado los materiales prístinos que formaban el disco protoplanetario. Estos materiales preservados están alojados en meteoritos no diferenciados. Los meteoritos procedentes de estos objetos, conocidos como condritas, son muestras de materiales formados en el disco protoplanetario alrededor del Sol hace unos 4.600 millones de años. Entre ellos, las condritas carbonáceas son las únicas muestras disponibles que representan asteroides carbonáceos que son importantes para comprender sus propiedades físicas y para comparar con las muestras retornadas por las misiones Hayabusa 2 y OSIRIS-Rex. Esta tesis se centra en la composición química, mineralogía, así como las propiedades físico-químicas de los cuerpos menores del Sistema Solar mediante medidas en el laboratorio de sus meteoritos. Diversas técnicas descritas aquí permiten el estudio de las propiedades de las condritas y, de esta manera, obtener claves sobre las complejas historias acrecionarias de sus cuerpos progenitores. Los cambios mineralógicos asociados al metamorfismo térmico, la alteración acuosa o a los efectos de choque en condritas son descritos en el contexto de indagar en la naturaleza de sus asteroides padres. Además, técnicas espectroscópicas son aplicadas como un método adecuado para asociar los meteoritos a sus asteroides específicos, aunque una asociación inequívoca requerirá completar misiones de retorno de muestras. En la primera parte de este trabajo se comparan los espectros de reflexión de dos grupos de condritas carbonáceas químicamente relacionados: CV y CK. Las propiedades reflectivas de esos dos grupos de condritas son comparados con la clase espectral Cg de asteroides. Dado que los asteroides han sido expuestos a impactos desde su formación sus superficies están cubiertas por pequeñas partículas, rocas y bloques mayores. La misión Hayabusa de JAXA recolectó partículas del regolito del asteroide 25143 Itokawa. Los estudios en el laboratorio de esas partículas proporcionan una oportunidad científica dado que sus propiedades físicas pueden ser comparadas con aquellas de las condritas que pueden ser consideradas buenos ejemplos de los materiales constitutivos de los asteroides potencialmente peligrosos (PHAs). En la segunda parte de la tesis se presentan los resultados del estudio de las propiedades mecánicas de tres de esas partículas usando una técnica precisa denominada nanoindentación. Finalmente también se estudian las propiedades de cuerpos oscuros asociados con cometas evolucionados. En ese sentido el cometa 2P/Encke es uno de los mayores objetos del llamado complejo de las Táuridas. Su comportamiento espectral hace que sea similar a las condritas carbonáceas prístinas, pero se conocía bien poco a su naturaleza real. En este trabajo se ha encontrado un buen ajuste espectral entre el cometa y dos condritas carbonáceas sin agrupar, lo que permite hacernos una idea sobre la composición heterogénea de la superficie de un cometa de periodo corto. To understand the solar system in its current form, and the formation of the planets, small bodies play a key role. The composition of asteroids and comets provides the clues about the birth of the solar system and its evolution. Small undifferentiated bodies contain the first solid materials of the Solar System, formed from the aggregation and melting of primordial dust. From these primordial building blocks much larger bodies such as asteroids, comets and planets were formed. Rocky bodies with a size of few hundreds of kilometers experienced chemical segregation due to differentiation, but the smaller ones irradiated the internal heat and never melted. These undifferentiated bodies have preserved pristine materials that were forming the protoplanetary disk. These materials are hosted by undifferentiated meteorites. The meteorites coming from these objects, known as chondrites, are samples of materials formed in the protoplanetary disk around the Sun about 4,600 million years ago. Among them, the carbonaceous chondrites are the only available samples representing carbonaceous asteroids which are important to understand their physical properties and for future comparison with samples returned by Hayabusa 2 and OSIRIS-Rex missions. This thesis focuses on the chemical composition, mineralogy, as well as the physical and mechanical properties of Solar System small bodies through laboratory measurements of their meteorites. Several techniques described here allow the study of the properties of chondrites, and therefore provide clues about the complex accretionary histories of their parent bodies. The mineralogical changes associated with thermal metamorphism, aqueous alteration, or to the effects of shock in chondrites are described here in the context of getting clues about their possible parent asteroids. Besides, spectroscopic techniques are applied as a suitable method to link the meteorite samples to specific asteroids, although an unambiguous association will require to complete future sample return missions. In the first part of the work, the reflectance spectra of two chemically-related carbonaceous chondrites groups, precisely the CVs and CKs are measured and compared. The reflective properties of these two chondrite groups and the comparison with the Cg asteroid reflectance class supports a common formation scenario. Asteroids have been exposed to impacts since their formation, and as a consequence their surfaces are covered by small particles, pebbles, and boulders. The Japanese JAXA Hayabusa mission collected particles from the regolith of asteroid 25143 Itokawa. Laboratory studies of these particles provide a scientific opportunity as their physical properties can be compared with those characteristic of chondrites that can be considered proxies of the building materials of potentially hazardous asteroids (PHAs). In the second part of the thesis the results from a study of the mechanical properties of three of these particles using a precise technique called nanoindentation are presented. Finally, the properties of dark bodies associated with evolved comets are studied. In that sense, comet 2P/Encke is one of the largest object of the so-called Taurid complex. Its spectral behaviour makes it similar to pristine carbonaceous asteroids, but little was known about its real nature. In this work a good spectral match between this comet and two ungrouped chondrites has been found, allowing us to make a first-guess about the heterogeneous composition of the surface of a short-period comet. Universitat Autònoma de Barcelona. Programa de Doctorat en Física

'La Terra acaba de capturar una nova lluna.' Aquesta frase podria ser l'inici per a una història de ficció o un conte infantil. Com les llunes que visita El petit príncep, d'Antoine de Saint-Exupéry, un d'aquells textos poètics i filosòfics que és bo anar rellegint de tant en tant, en les diferents etapes de la vida, per gaudir-lo de manera diferent. La Lluna sempre ha estimulat la imaginació d'escriptors i aventurers, ha servit de guia a camperols i navegants, ha exercit una poderosa atracció sobre els enamorats. Tanmateix, la frase que obre aquest article és absolutament certa: a finals de setembre la NASA va anunciar que la Terra havia capturat un petit asteroide de la mida d'un cotxe, que s'ha convertit en una nova lluna. S'estarà uns quants mesos orbitant la Terra, fins que aconsegueixi escapar i tornar a emprendre el seu camí sideral. De Lluna 'lluna', però, seguirem tenint la mateixa. Des de la perspectiva científica, és un astre ben misteriós, atès que sempre ens mostra la mateixa cara, com a conseqüència de la combinació del període de rotació i de translació al voltant de la Terra. Misteriós però tanmateix molt útil, atès que la seva periodicitat ha estat utilitzada des de l'antigor per mesurar el temps i predir els canvis estacionals.

Small bodies, like comets and asteroids, are of interest for the study of the origin of the Solar System since they have experienced little changes throughout time. Therefore, by understanding their evolution we can learn about the evolution of the Solar System itself. This information can be useful for future space exploration or for planetary defense. Nowadays, there are several space missions studying or about to study small bodies, but only a few instruments are destined to study the interior of small body cores.Radio waves interact with the medium they are propagating through and will undergo different modifications depending on the properties of the material. Therefore, radar is the ideal method to study the internal structure of an asteroid. The wave's properties, such as its velocity, will be affected by its travel through the nucleus dependent on the dielectric properties of the asteroid. We propose a new bi-static low-frequency radar (LFR) based on the instrument CONSERT which was onboard the Rosetta mission. This LFR primary objective is to measure the propagation delay between two electronics, one posed on the asteroid’s surface and the other orbiting around it. The signal will be transmitted through the body’s nucleus and will be affected by its composition and heterogeneity. By measuring different signal characteristics, such as the propagation delay, we can deduce the composition properties of the object.The main objective of this thesis is to study and understand how the clock drift between radar electronics will affect the measurement of the propagation delay in order to propose compensation methods to improve science return. The initial step of the thesis is to provide an understanding of the clock signal generation and how the stability of the signal will be affected over time by different processes like temperature, the voltage supply, or aging. To understand how these instabilities will impact the propagation delay measurement, we analyze the long scale drift of radar instruments. For this, we developed a time model of the radar based on time events. The model was used to build a simulator using a simple model of the clock signal generation. With this simulator, we show that the time errors have a different effect on the bi-static radar at different time scales, but that these different time scales are correlated. We propose a method to estimate clock drift from radar data to compensate for time errors.To validate the model, a test bench is designed and developed measuring time differences between two clocks. Using the test bench data as input for the simulator allows to estimate the impact on instrument performances and to estimate performances of the compensation methods. The data from the test bench is used for the validation of the selected clocks for the mission and will be used for their characterization. This clock characterization will help to improve the simulator for different tests, as we can include the real models for frequency instabilities.To conclude, we present the limitations of the compensation methods, as well as the improvements in the electronic design and operation of the instrument as a result of the time analysis., Les petits corps, comme les comètes et les astéroïdes, présentent un intérêt pour l’étude de l’origine du système solaire, car ils n’ont connu que peu de changements au fil du temps. Par conséquent, en comprenant leur évolution, nous pouvons en apprendre davantage sur l'évolution du système solaire lui-même. Cette information peut être utile pour une future exploration spatiale ou pour la défense planétaire. De nos jours, plusieurs missions spatiales étudient ou sont sur le point d’étudier les petits corps, mais seuls quelques instruments sont destinés à étudier l’intérieur des petits corps.Les ondes radio interagissent avec le milieu à travers lequel elles se propagent et subiront différentes modifications en fonction des propriétés du matériau. Par conséquent, le radar est la méthode idéale pour étudier la structure interne d'un astéroïde. Les propriétés de l'onde, telles que sa vitesse, seront affectées par son parcours dans le noyau en fonction des propriétés diélectriques de l'astéroïde. Nous proposons un nouveau radar bi-statique à basse fréquence (LFR) basé sur l'instrument CONSERT embarqué dans la mission Rosetta. L’objectif principal de ce LFR est de mesurer le temps de propagation entre deux composants électroniques, l’un posé sur la surface de l’astéroïde et l’autre en orbite autour de celui-ci. Le signal sera transmis à travers le noyau du corps et sera affecté par sa composition et son hétérogénéité. En mesurant différentes caractéristiques du signal, telles que le délai de propagation, nous pouvons en déduire les propriétés de composition de l'objet.L'objectif principal de cette thèse est d'étudier et de comprendre comment la dérive d'horloge entre les électroniques de radar affectera la mesure du temps de propagation afin de proposer des méthodes de compensation pour améliorer le retour scientifique. La première étape de la thèse consiste à fournir une compréhension de la génération du signal d'horloge et de la manière dont la stabilité du signal sera affectée dans le temps par différents processus tels que la température, l'alimentation en tension ou le vieillissement. Pour comprendre l'impact de ces instabilités sur la mesure du délai de propagation, nous analysons la dérive à grande échelle des instruments radar. Pour cela, nous avons développé un modèle temporel du radar basé sur des événements temporels. Le modèle a été utilisé pour construire un simulateur à l'aide d'un modèle simple de génération de signaux d'horloge. Avec ce simulateur, nous montrons que les erreurs de temps ont un effet différent sur le radar bi-statique à différentes échelles de temps, mais que ces différentes échelles de temps sont corrélées. Nous proposons une méthode pour estimer la dérive de l'horloge à partir des données radar afin de compenser les erreurs de temps.Pour valider le modèle, un banc de test est conçu et développé en mesurant les différences de temps entre deux horloges. En utilisant les données du banc d'essai comme entrée pour le simulateur permet d'estimer l'impact sur les performances des instruments et d'estimer les performances des méthodes de compensation. Les données du banc d’essai sont utilisées pour la validation des horloges sélectionnées pour la mission et seront utilisées pour leur caractérisation. Cette caractérisation d'horloge aidera à améliorer le simulateur pour différents tests, car nous pouvons inclure les modèles réels d'instabilités de fréquence.Pour conclure, nous présentons les limites des méthodes de compensation, ainsi que les améliorations apportées à la conception électronique et au fonctionnement de l'instrument à la suite de l'analyse temporelle.

Small bodies, like comets and asteroids, are of interest for the study of the origin of the Solar System since they have experienced little changes throughout time. Therefore, by understanding their evolution we can learn about the evolution of the Solar System itself. This information can be useful for future space exploration or for planetary defense. Nowadays, there are several space missions studying or about to study small bodies, but only a few instruments are destined to study the interior of small body cores.Radio waves interact with the medium they are propagating through and will undergo different modifications depending on the properties of the material. Therefore, radar is the ideal method to study the internal structure of an asteroid. The wave's properties, such as its velocity, will be affected by its travel through the nucleus dependent on the dielectric properties of the asteroid. We propose a new bi-static low-frequency radar (LFR) based on the instrument CONSERT which was onboard the Rosetta mission. This LFR primary objective is to measure the propagation delay between two electronics, one posed on the asteroid’s surface and the other orbiting around it. The signal will be transmitted through the body’s nucleus and will be affected by its composition and heterogeneity. By measuring different signal characteristics, such as the propagation delay, we can deduce the composition properties of the object.The main objective of this thesis is to study and understand how the clock drift between radar electronics will affect the measurement of the propagation delay in order to propose compensation methods to improve science return. The initial step of the thesis is to provide an understanding of the clock signal generation and how the stability of the signal will be affected over time by different processes like temperature, the voltage supply, or aging. To understand how these instabilities will impact the propagation delay measurement, we analyze the long scale drift of radar instruments. For this, we developed a time model of the radar based on time events. The model was used to build a simulator using a simple model of the clock signal generation. With this simulator, we show that the time errors have a different effect on the bi-static radar at different time scales, but that these different time scales are correlated. We propose a method to estimate clock drift from radar data to compensate for time errors.To validate the model, a test bench is designed and developed measuring time differences between two clocks. Using the test bench data as input for the simulator allows to estimate the impact on instrument performances and to estimate performances of the compensation methods. The data from the test bench is used for the validation of the selected clocks for the mission and will be used for their characterization. This clock characterization will help to improve the simulator for different tests, as we can include the real models for frequency instabilities.To conclude, we present the limitations of the compensation methods, as well as the improvements in the electronic design and operation of the instrument as a result of the time analysis.; Les petits corps, comme les comètes et les astéroïdes, présentent un intérêt pour l’étude de l’origine du système solaire, car ils n’ont connu que peu de changements au fil du temps. Par conséquent, en comprenant leur évolution, nous pouvons en apprendre davantage sur l'évolution du système solaire lui-même. Cette information peut être utile pour une future exploration spatiale ou pour la défense planétaire. De nos jours, plusieurs missions spatiales étudient ou sont sur le point d’étudier les petits corps, mais seuls quelques instruments sont destinés à étudier l’intérieur des petits corps.Les ondes radio interagissent avec le milieu à travers lequel elles se propagent et subiront différentes modifications en fonction des propriétés du matériau. Par conséquent, le radar est la méthode idéale pour étudier la structure interne d'un astéroïde. Les propriétés de l'onde, telles que sa vitesse, seront affectées par son parcours dans le noyau en fonction des propriétés diélectriques de l'astéroïde. Nous proposons un nouveau radar bi-statique à basse fréquence (LFR) basé sur l'instrument CONSERT embarqué dans la mission Rosetta. L’objectif principal de ce LFR est de mesurer le temps de propagation entre deux composants électroniques, l’un posé sur la surface de l’astéroïde et l’autre en orbite autour de celui-ci. Le signal sera transmis à travers le noyau du corps et sera affecté par sa composition et son hétérogénéité. En mesurant différentes caractéristiques du signal, telles que le délai de propagation, nous pouvons en déduire les propriétés de composition de l'objet.L'objectif principal de cette thèse est d'étudier et de comprendre comment la dérive d'horloge entre les électroniques de radar affectera la mesure du temps de propagation afin de proposer des méthodes de compensation pour améliorer le retour scientifique. La première étape de la thèse consiste à fournir une compréhension de la génération du signal d'horloge et de la manière dont la stabilité du signal sera affectée dans le temps par différents processus tels que la température, l'alimentation en tension ou le vieillissement. Pour comprendre l'impact de ces instabilités sur la mesure du délai de propagation, nous analysons la dérive à grande échelle des instruments radar. Pour cela, nous avons développé un modèle temporel du radar basé sur des événements temporels. Le modèle a été utilisé pour construire un simulateur à l'aide d'un modèle simple de génération de signaux d'horloge. Avec ce simulateur, nous montrons que les erreurs de temps ont un effet différent sur le radar bi-statique à différentes échelles de temps, mais que ces différentes échelles de temps sont corrélées. Nous proposons une méthode pour estimer la dérive de l'horloge à partir des données radar afin de compenser les erreurs de temps.Pour valider le modèle, un banc de test est conçu et développé en mesurant les différences de temps entre deux horloges. En utilisant les données du banc d'essai comme entrée pour le simulateur permet d'estimer l'impact sur les performances des instruments et d'estimer les performances des méthodes de compensation. Les données du banc d’essai sont utilisées pour la validation des horloges sélectionnées pour la mission et seront utilisées pour leur caractérisation. Cette caractérisation d'horloge aidera à améliorer le simulateur pour différents tests, car nous pouvons inclure les modèles réels d'instabilités de fréquence.Pour conclure, nous présentons les limites des méthodes de compensation, ainsi que les améliorations apportées à la conception électronique et au fonctionnement de l'instrument à la suite de l'analyse temporelle.

Dissertação de Mestrado em Astrofísica e Instrumentação para o Espaço apresentada à Faculdade de Ciências e Tecnologia O desenvolvimento da tecnologia e da ciência tem permitido conhecer melhor o nosso sistema solar e de que forma a caracterização de asteróides é importante para a evolução científica e para assegurar a sobrevivência da nossa espécie. Esta dissertação de mestrado apresenta o desenvolvimento de uma metodologia de análise e processamento de imagens de grande campo, obtidas em um observatório terrestre, para identificação e caracterização de asteróides conhecidos. Este trabalho tem como base o uso de ferramentas Observatório Virtual, de acesso livre e que poderão ser utilizadas por qualquer utilizador. De modo a automatizar todo o processo serão utilizados e adaptados alguns scripts anteriormente desenvolvidos pelo grupo científico e adicionados novos scripts complementares. Dos dados fornecidos serão calculados os centróides das fontes de luz correspondentes a objectos estáticos (como no caso das estrelas) e correspondentes a objectivos que apresentam movimento (como no caso dos asteróides) e serão realizadas calibrações astrométricas com o objectivo de obter as coordenadas celestes (ascensão recta e declinação) para cada uma das fontes. Também serão realizadas calibrações fotométricas de modo a obter as magnitudes aparentes de cada fonte, para posteriormente obter as magnitudes absolutas de cada posição dos asteróides e para extrair as suas curvas de luz. Se a quantidade e qualidade dos dados permitir serão ainda calculados os seus períodos. Após analise dos dados fornecidos, os resultados serão submetidos para a base de dados Minor Planet Center, onde poderão ser aprovados para a calibração das orbitas dos asteróides em estudo. The development of technology and science allowed us to know more about our solar system and how the characterization of asteroids is important for scientific evolution and to ensure the survival of our species. This dissertation presents the development of a methodology to analyze and process large field images, obtained by a ground-based observatory, to identify and characterize known asteroids. This work is based on use of Virtual Observatory tools, of free access and which can be used by any user. In order to automate the whole process, some scripts previously developed by the scientific group will be used along with newly-added complementary scripts. From the astronomical data, the centroids of light sources of non-moving objects (for example stars, bad pixels, etc.) and moving objects (for example asteroids) will be calculated and astrometric calibrations will be performed in order to obtain the celestial coordinates (right ascension and declination) for each light source. Photometric calibrations will be performed in order to obtain the apparent magnitude of each source, to obtain the absolute magnitude of each asteroid position and to extract their light curves. If the quantity and quality of the data allows us, their periods will be calculated using a well-known periodogram tool. After analyzing the provided data, the results will be submitted to the Minor Planet Center of the International Astronomical Union, where they can be approved for calibration of the orbits of the asteroids under study.

Agradecimentos: This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. NNX17AF21G issued through the SSO Planetary Astronomy Program, and by NSF grant AST-1515015. S.J.H. is supported by the NSF Graduate Research Fellowship Grant No. DGE 1256260. This research has made use of data and services provided by the International Astronomical Union's Minor Planet Center. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the of SMinistry of Science and Education pain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, FINEP - FINANCIADORA DE ESTUDOS E PROJETOS, Fundacdo Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and the Ministerio da Ciencia, Tecnologia e Inovacao, the Deutsche Forschungsgemeinschaft and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigations Energeticas, Medioambientales y Tecnologicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenossische Technische Hochschule (ETH) Zurich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciencies de l'Espai (IEEC/CSIC), the Institut de Fisica d'Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universitat Munchen and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium. The DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020, and the Brazilian Institute Nacional de Ciencia e Tecnologia (INCT) e Universe (CNPq grant 465376/2014-2). This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes Abstract: In the current model of early Solar System evolution, the stable members of the Jovian and Neptunian Trojan populations were captured into resonance from the leftover reservoir of planetesimals during the outward migration of the giant planets. As a result, both Jovian and Neptunian Trojans share a common origin with the primordial disk population, whose other surviving members constitute today's trans-Neptunian object (TNO) populations. The cold (low inclination and small eccentricity) classical TNOs are ultra-red, while the dynamically excited "hot" (high inclination and larger eccentricity) population of TNOs contains a mixture of ultra-red and blue objects. In contrast, Jovian and Neptunian Trojans are observed to be blue. While the absence of ultra-red Jovian Trojans can be readily explained by the sublimation of volatile material from their surfaces due to the high flux of solar radiation at 5 AU, the lack of ultra-red Neptunian Trojans presents both a puzzle and a challenge to formation models. In this work we report the discovery by the Dark Energy Survey (DES) of two new dynamically stable L4 Neptunian Trojans, 2013 VX30 and 2014 UU240, both with inclinations i gt; 30 degrees, making them the highest-inclination known stable Neptunian Trojans. We have measured the colors of these and three other dynamically stable Neptunian Trojans previously observed by DES, and find that 2013 VX30 is ultra-red, the first such Neptunian Trojan in its class. As such, 2013 VX30 may be a "missing link" between the Trojan and TNO populations. Using a simulation of the DES TNO detection efficiency, we find that there are 162 +/- 73 Trojans with H-r < 10 at the L4 Lagrange point of Neptune. Moreover, the blue-to-red Neptunian Trojan population ratio should be higher than 17:1. Based on this result, we discuss the possible origin of the ultra-red Neptunian Trojan population and its implications for the formation history of Neptunian Trojans CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ FINANCIADORA DE ESTUDOS E PROJETOS - FINEP FUNDAÇÃO CARLOS CHAGAS FILHO DE AMPARO À PESQUISA DO ESTADO DO RIO DE JANEIRO - FAPERJ Fechado

Outgoing

En este trabajo presentamos un nuevo código de evolución colisional del Cinturón de Asteroides, ubicado entre Marte y Jupiter. Ceres y Vesta son los cuerpos más grandes y masivos del cinturón de Asteroides. Si bien no han sufrido impactos catastróficos, han transcurrido por eventos de craterización. Se ha detectado una familia de asteroides asociada a Vesta, sin embargo, ninguna se ha encontrado para Ceres. En este trabajo, realizamos simulaciones numéricas que representan la evolución colisional del cinturón de asteroides a lo largo de la edad del Sistema Solar. Para ello, desarrollamos un código que sigue el modelo delineado por el código BOULDER en el que, para una dada colisión entre 2 asteroides, se predice la masa del mayor remantente, mayor fragmento y la pendiente de la distribución acumulada de fragmentos. Además, para una descripción más realista del mismo, realizamos una división del Cinturón de Asteroides en 6 poblaciones (inner, middle, pristine, outer, cybele, high inclination), delimitadas por las resonancias de movimientos medios con Jupiter, considerando sus respectivas probablilidades y velocidades de impactos mutuos. Este trabajo permitirá cuantificar la tasa generación de fragmentos de Ceres y Vesta, y la vinculación entre dichos fragmentos con las poblaciones de NEAs y otros asteroides del cinturón., Universidad Nacional de La Plata

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) A solução para o problema restrito de três corpos, proposta por Lagrange, prevê a possibilidade de duas regiões de equilíbrio estável, onde corpos menores podem orbitar, um corpo central, com semi-eixo maior similar ao de um corpo maior. Os corpos localizados nestas regiões são conhecidos como troianos. Esses objetos, em especial os Troianos do planeta Júpiter, têm se mostrado importantes peças na formação e evolução dinâmica do Sistema Solar. Vários modelos de evolução dinâmica foram desenvolvidos nos últimos anos, sendo o mais aceito pela comunidade científica o modelo de Nice - Jumping Jupiter. Esse modelo explica que os Troianos foram formados junto aos corpos do cinturão de Kuiper e, durante a migração das órbitas dos planetas gigantes, eles teriam sido capturados nessas regiões de equilíbrio. Atualmente, são conhecidos mais de sete mil Troianos com órbitas determinadas. Entretanto existem poucas informações a respeito das propriedades físicas desses corpos. Para realizar a caracterização desses objetos de forma precisa, propõe-se a utilização da técnica de ocultações estelares. Esse método consiste no registro do aparente bloqueio da luz de uma estrela, quando um corpo do sistema solar interpõe-se entre a estrela e o observador. As ocultações estelares permitem a determinação de tamanhos e formas de objetos com precisão da ordem do quilômetro e, por consequência a derivação de outros parâmetros físicos, como albedo e densidade, com grande precisão. Além disso, é possível verificar a existência de anéis, satélites e atmosfera nesses pequenos corpos. Para se observar uma ocultação é necessário prever quando e onde esse evento ocorrerá. Nesse procedimento são comparadas as posições do objeto e da estrela ao longo do tempo, o que requer boas efemérides do objeto e boa posição das estrelas. Atualmente, as posições das estrelas são obtidas da segunda versão do catálogo Gaia, que possui precisões na ordem do milissegundo de arco (mas). Contudo as efemérides possuem imprecisões que podem chegar a centenas de mas. Isto é muito maior que a dimensão aparente do próprio objeto. Para melhorar as efemérides é preciso acrescentar novas posições dos corpos, para um novo ajuste de órbita, tarefa dificultada pelo baixo brilho destes objetos. Por esse motivo propõe-se a utilização de observações oriundas de imagens obtidas fortuitamente por grandes surveys. Neste trabalho, fez-se a busca e seleção de objetos Troianos a partir do banco de dados de apontamentos do Dark Energy Survey (DES). Destas observações, obteve-se novas posições, que foram usadas para a melhora de efemérides. Filtrando os apontamentos do DES, e incluindo os principais objetos conhecidos, foram selecionados um total de 54 troianos de Júpiter. Desenvolveu-se uma ferramenta para o cálculo de predições de ocultações estelares, com a qual obteve-se aproximadamente quarenta e um mil eventos no intervalo de março de 2018 a dezembro de 2020. Essas predições são disponibilizadas em sites dedicados e softwares para a difusão e realização de campanhas observacionais. Vale citar que dois eventos envolvendo dois Troianos, Leucus e Ennomos, já foram detectados por colaboradores do grupo. The solution of the restricted three-body problem, proposed by Lagrange, provides two regions of possible stable equilibrium, where smaller bodies can orbit a central body with a semi-major axis similar to that of a larger body. The bodies located in these regions are known as trojans. It has been shown that these objects, especially the Trojans of the planet Jupiter, are important pieces in the formation and dynamic evolution of the Solar System. Several models of dynamic evolution have been developed in recent years, with the Jumping Jupiter Nice model being largely accepted by the scientific community. This model claims that the Trojans were formed in the Kuiper belt region and, during the migration of the orbits of the giant planets, they were captured in those equilibrium regions. Currently, there are more than seven thousand Trojans with determined orbits, but there is little information on the physical properties of these bodies. In order to derive their physical properties very accurately, the use of the stellar occultation technique is proposed. This method consists of recording the apparent blockage of a star’s light when a body of the solar system is interposed between the star and the observer. Stellar occultations allow the determination of object sizes and shapes with accuracy in the order of the kilometer, and consequently the determination of other physical parameters such as albedo and density with great precision. In addition, it is possible to verify the existence of rings, satellites and atmosphere in these small bodies. In order to observe an occultation, it is necessary to predict when and where this event will occur. In this procedure the positions of the object and of the star are compared over time, which requires good ephemerides of the object and good position of the stars. At present, the positions of the stars are obtained from the second version of the Gaia catalog, which has precisions in the order of the milliarcsecond (mas), yet the ephemerides have imprecision that can reach a hundred mas, what is much larger than the apparent dimension of the object itself. To improve the ephemeris it is necessary to add new positions of the bodies, for a new adjustment of orbit, difficult task due to the low brightness of these objects. For this reason, it is proposed the use observations from images randomly obtained by large surveys. In this work, the search and selection of Trojan objects was done from the observational database of the Dark Energy Survey (DES). From these observations, new positions were obtained, which were used to improve the object’s ephemerides. Filtering DES observations, and including the main known objects, a total of 54 Jupiter Trojans were selected. A tool was developed to predict stellar occultations, with which approximately fortyone thousand events were obtained in the interval from March 2018 to December 2020. These predictions are made available on websites and software for the diffusion and realization of observational campaigns. It is worth mentioning that two events involving two Trojans, Leucus and Ennomos, have been already detected by collaborators of the group.

In response to the current interest in CubeSats and potential applications for planetary exploration, this work studies the feasibility of using autonomous CubeSats to flyby near-Earth asteroids. Considering the limited performance of current propulsion systems for CubeSats, low-energy (impulsive and low-thrust) trajectories are designed to encounter near-Earth asteroids in the medium-fidelity Circular Restricted Three-Body Problem, and their existence in a high-fidelity ephemeris model is also verified. The use of large ground antennas for deep-space communications might represent a major portion of CubeSat mission budgets, and thus the feasibility of performing optical navigation to autonomously estimate and correct the trajectory of the CubeSat is also evaluated through Monte Carlo simulations. Preliminary results show that approximately 4 asteroids per year could be reached by a 3U CubeSat if deployed around the first or second Sun-Earth Lagrange points. According to the limited performance of current CubeSat components, flyby altitudes of the order of 100–500 kilometers are determined possible using only observations of the Sun and of the target asteroid for autonomous navigation. Keywords: Interplanetary CubeSats; near-Earth asteroids; trajectory design; autonomous navigation

Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2018, Director: Gerardo Gómez Muntané, [en] Asteroids are of strategic importance for science in an effort to uncover the formation, evolution and composition of the Solar System. Near-Earth objects (NEOs) are of particular interest because of their accessibility from Earth. In this work, we will study the mathematical models, methods and techniques needed to design an asteroid retrieval. This line of research has multiple aplications, such as mitigating the hazard posed by an asteroid impact; or the obtention of resources via asteroid mining. We will analise some dynamical models used to envisage an asteroid orbit. We will take profit of the dynamics of these models to minimize the required energy to perform an asteroid capture. Different transfer techniques in each of these models will be shown. At last, we will explain the whole process behind an asteroid retrieval: from the asteroids database selection, to the construction and posterior refinement of the transfer trajectory.