L'existence de molécules interstellaires soulève une question, ces molécules sont-elles les mêmes molécules que nous voyons dans le système Solaire aujourd'hui ? C'est une question toujours ouverte qui implique des conséquences profondes. Il est possible d’éclaircir cette question en étant capables de retracer l'héritage d'un groupe de molécules chimiquement liées, ce que nous appelons un réservoir. Le meilleur outil pour retracer l'héritage des réservoirs sont les rapports isotopiques. L'élément qui montre les plus grandes variations du rapport isotopique dans le système Solaire est l'azote. Ces variations indiquent que le rapport isotopique de l'azote est sensible aux conditions physiques de la formation des étoiles.L'objectif principal de cette thèse est d'identifier les réservoirs d'azote à différents étapes de la formation des étoiles et des planètes. La première étape de cette entreprise était d'identifier le rapport isotopique de la masse principal d'azote du milieu interstellaire local aujourd'hui.Cela a été déterminé égale à 323 ± 30 à partir du rapport CN/C 15 N mesuré dans le disque protoplanétaire autour de TW Hya. Parallèlement à cela, nous avons également mesuré un rapport HCN/HC 15 N=128 ± 36 dans le disque protoplanétaire autour de MWC 480. Ces rapports isotopiques très distinctes mesurées sur les disques protoplanétaires sont une indication claire de la présence d'au moins deux réservoirs d'azote dans les disques protoplanétaires. La façon dont ces réservoirs se séparent est cependant inconnue. Cela pourrait peut-être se produire en raison de réactions de fractionnement chimique ayant lieu dans les cœurs prestellaires. Nous avions donc comme objectif d'obtenir une mesure précise et directe du rapport isotopique de l'azote des molécules d'HCN dans le cœur prestellaire L1498.Pour obtenir cette mesure, l'obstacle le plus important à surmonter était due aux anomalies hyperfines des molécules d'HCN. Ces anomalies hyperfines sont induites par le chevauchement des composants hyperfins. Ceci sont particulièrement sensibles à la densité de colonne d'HCN, mais aussi au champ de vitesses et aux largeurs de raies. Ainsi les anomalies hyperfines sont un outil de mesure de l'abondance d'HCN permettant aussi de sonder la cinématique des cœurs prestellaires.Pour reproduire avec précision les anomalies hyperfines, et ainsi mesurer des densités de colonne précises d'HCN, nous avions besoin d'explorer un espace de paramètres dégénéré de 15 dimensions. Pour minimiser les dégénérescences nous avons obtenu un profil de densité basé sur des cartes du continuum de L1498. Ceci permettant de réduire à 12 dimensions l'espace des paramètres. L'exploration de cet espace de paramètre a été fait grâce à l'utilisation d'un méthode de minimisation MCMC. Grâce à cette exploration, nous avons obtenu HCN/HC 15 N = 338 ± 28 et HCN/H 13 CN = 45 ± 3. Les incertitudes sur ces valeurs sont limités par les erreurs de calibration et sont dé-terminés de manière non arbitraire par le méthode MCMC. Les implications de ces résultats sont discutées dans le chapitre de conclusion,où nous présentons également quelques perspectives sur l'avenir. / The existence of interstellar molecules raises the question, are thesemolecules the same molecules we see on the Solar system today? Thisis still an open question with far reaching consequences. Some lightmay be shed on this issue if we are able to trace the heritage of agroup of chemically linked molecules, a so-called reservoir. The besttool to trace the heritage of reservoirs are isotopic ratios. The elementthat shows the largest isotopic ratio variations in the Solar system isnitrogen. For this is an indication that the isotopic ratio of nitrogen issensitive to the physical conditions during star formation.The main objective of this thesis is to identify the reservoirs of ni-trogen at different stages of star and planet formation. The first stepin this endeavour was to identify the isotopic ratio of the bulk of ni-trogen in the local ISM today. This was determined to be 323 ± 30from the CN/C 15 N ratio in the protoplanetary disk around TW Hya.Along with it we also measured the HCN/HC 15 N= 128 ± 36 in theprotoplanetary disk around MWC 480. This very distinct nitrogen iso-topic ratios on protoplanetary disks are a clear indication that thereare at least two reservoirs of nitrogen in protoplanetary disks. Howthese reservoirs get separated is however unknown. This could pos-sibly happen due to chemical fractionation reactions taking place inprestellar cores. We therefore aimed to obtain an accurate direct mea-surement of the nitrogen isotopic ratio of HCN in the prestellar coreL1498.To obtain this measurement the most important hurdle to overcomewere the hyperfine anomalies of HCN. These hyperfine anomaliesarise due to the overlap of hyperfine components. They are especiallysensitive to the column density of HCN, but also to the velocity fieldand line widths. Thus hyperfine anomalies are a tool to measure theabundance of HCN and to probe the kinematics of prestellar cores.To accurately reproduce the hyperfine anomalies, and thus mea-sure accurate column densities for HCN, we needed to explore adegenerate parameter space of 15 dimensions. To minimise the de-generacies we have derived a density profile based on continuummaps of L1498. This reduced the parameter space to 12 dimensions.The exploration of this parameter space was done through the useof a MCMC minimisation method. Through this exploration we ob-tained HCN/HC 15 N = 338 ± 28 and HCN/H 13 CN = 45 ± 3. Theuncertainties on these values are calibration limited and determinednon-arbitrarily by the MCMC method. Implications of these resultsare discussed in the concluding chapter, where we also present somefuture perspectives.

Les grains de poussière se trouvant dans les nuages moléculaires denses jouent un grand rôle dans la formation de molécules organiques complexes. Ces grains sont recouverts d'un manteau glacé contenant des molécules primitives. Au cours de l'évolution des nuages moléculaires vers des systèmes planétaires, les grains sont soumis à des processus énergétiques transformant la matière organique présente dans les glaces. Les grains finissent par être intégrés dans les petits corps du système solaire tels que les comètes et les astéroïdes. Cette thèse cherche à simuler en laboratoire l'évolution chimique de ces glaces. Des analogues de ces glaces sont formés sur un substrat à basse température, et sont irradiés avec des photons UV et/ou réchauffés afin de simuler les processus astrophysiques. On forme ainsi un résidu organique que l'on caractérise grâce à la spectroscopie infrarouge à transformée de Fourier (IRTF) et la spectrométrie de masse à très haute résolution (VHRMS) par Orbitrap.Nous avons d'abord effectué des études mécanistiques centrées autour de la formation d'aminoalcools et d'hydroxynitriles lors du réchauffement de glaces contenant de l'acétaldéhyde (CH$_3$CHO) ou de l'acétone ((CH$_3$)$_2$CO) avec NH$_3$, HCN et H$_2$O. Nous avons ensuite étudié la composition globale de résidus issus de l'irradiation et du réchauffement de glaces contenant H$_2$O, CH$_3$OH, et NH$_3$. Nous présentons une nouvelle approche pour interpréter les données Orbitrap de ces résidus. Les similarités trouvées avec des analyses de matière organique météoritique issues de la littérature laissent à penser qu'une partie de son évolution pourrait être semblable à celle de nos résidus. / Dust grains located in dense molecular clouds play a major role in the formation of complex organic molecules. These grains are covered by icy mantles containing primitive molecules. Dense molecular clouds can collapse and lead to the formation of planetary systems such as our own. During this evolution, the grains are exposed to energetic processes which transform the organic matter inside the ices. The grains are ultimately incorporated into small solar system bodies such as comets and asteroids, which can then contribute to the exogenous delivery of organic matter on Earth. In this context, this thesis focuses on simulating the chemical evolution of ices. To that end, ice analogues are formed by condensing a relevant gas mixture on a cold substrate. These interstellar ice analogues are irradiated with UV photons and/or heated in order to simulate astrophysical processes. An organic residue is formed which we characterized with Fourier transform infrared spectroscopy (FTIR) and very high resolution mass spectrometry (VHRMS) by Orbitrap.First, we performed mechanistic studies focused on the formation of aminoalcohols and hydroxynitriles from the warming of ices containing acetaldehyde (CH$_3$CHO) or acetone ((CH$_3$)$_2$CO) with NH$_3$, HCN and H$_2$O. Secondly, we studied the global composition of residues made from irradiation and warming of ices containing H$_2$O, CH$_3$OH, and NH$_3$. We present a new approach to interpret Orbitrap data of the residues. Similarities observed with meteoritic organic matter analyses found in the literature could mean that some of the evolution that led to meteoritic organic matter is shared with the evolution of our residues.

Les petits corps du système solaire riches en volatiles incluent plusieurs populations d’objets : les astéroïdes de la ceinture principale, les astéroïdes troyens des planètes géantes, les objets trans-neptuniens (OTNs) et les comètes. Au cours de ces dernières années, l'’idée que leur position actuelle résulte de migrations orbitales plutôt qu’elle ne reflète leur région de formation a progressivement émergée. Spécifiquement, certains astéroïdes pourraient être des comètes, et certaines comètes pourraient être des OTNs. Je présente ici les travaux réalisés au cours de ma thèse pour contraindre la composition (minéralogie de surface et structure interne) de ces différentes populations afin i) de déterminer les liens qui les unissent, ii) comprendre leurs migrations passées et donc, iii) apporter de nouvelles contraintes aux modèles dynamiques décrivant la formation et l’évolution de notre système solaire. À cet effet, j’ai principalement utilisé comme méthode d’analyse l’observation spectroscopique, ainsi que la modélisation des données obtenues et leur comparaison aux données spectrales de météorites et poussières cosmiques étudiées en laboratoire. / The icy small bodies of our solar system encompass several populations of objects : the main belt asteroids, the giant planets Trojans, the Trans-Neptunian Objects (TNOs) and the comets. During recent years, the idea that their present location is the result of orbital migrations rather than their true formation location has progressively emerged. Specifically, some asteroids could be comets, and some comets could be TNOs. Here, I present the studies carried out along my PhD aiming to constrain the physical properties of all these populations in order ultimately i) to determine the link between these populations, ii) bring key constraints to their past orbital evolution and thus iii) key constraints to the formation and evolution models for our Solar System. For that purpose, I have used spectroscopy as a main tool, as well as data modelling using a radiative transfert code and comparison of our astronomical data to laboratory measurements of meteorites and cosmic dust.

Yes / In this paper, a novel multilink selection framework is developed for different applications with various quality of service (QoS) requirements in avionic systems, based on the multi-attribute decisionmaking model. Two metaheuristic algorithms are proposed to solve this model while optimizing the multilink selection performances. Multilink configuration and multi-homing capabilities are generally required for aircrafts operating in a heterogeneous wireless network environment. The first algorithm, called Analytic Hierarchy Process and Simulated Annealing (AHP-SA), utilises a two-phase process. In Phase one, an analytic hierarchy process (AHP) is used to choose the decision weight factors. Then, in Phase two, a simulated annealing process is applied to select suitable networks, for various service requests, based on the weights obtained from first phase. Further, to improve customer satisfaction, Simulated Annealing algorithm for Simultaneous Weights and Network Selection Optimisation (SA-SWNO) is developed, in which a simulated annealing algorithm is applied to dynamically optimise weight factors of objective functions and the request-to-network assignment matrix. Simulation results demonstrates that both proposed algorithms outperform the commonly used price-based or QoS-based network selection scheme with much higher averaged satisfaction degree and lower computational complexity. / Cockpit NetwOrk CoMmunications Environment Testing (COMET) Project under the European Commission’s Program Clean Sky2 in partnership with the European Aeronautical Industry

Planetary systems are not only composed of planets, but also of km-sized rocky and icy bodies that are confined within belts similar to the Asteroid and Kuiper belt in the Solar System. Mutual collisions within these belts grind down solids producing dust and giving rise to debris discs. Primitive asteroids and comets likely played a major role in the emergence of life on Earth through their delivery of volatiles early in the lifetime of our planet. Cometary impacts, therefore, could be a necessary condition for the emergence of life in exoplanets and the study of debris discs essential to determine the ubiquity of such phenomenon. Moreover, exocometary discs provide a unique window into the origins and outer regions of planetary systems as comets do within our Solar System. Initially, in Chapter 1 I present an overview of the study of exoplanetary systems, focusing on debris discs. I discuss the basics of planet formation, its connection with debris discs, and how these evolve and interact with planets. I also describe how we observe these discs and probe their volatile component that is locked inside exocomets, and some evidence supporting the idea of exocomets venturing into the inner regions of planetary systems. Then, in Chapters 2, 3, 4 and 5 I present new ALMA observations of the systems HD 181327, η Corvi, the multiplanet system 61 Vir and HD 107146, which host debris discs. In the first two, I highlight the derivation of the density structure of their discs and the detection of volatiles being released by exocomets; while in the third and fourth I compare the observations with simulations, which I use to set constraints on the underlying planetesimal distribution and mass and orbital distance of unseen planets. Finally, in Chapter 6 I present result obtained from N-body simulations to study the process of inward transport of comets by a multiplanetary system and how these can deliver material to inner planets and explain the frequently observed exozodiacal dust. To conclude, in Chapter 7 I summarise the results and conclusions of this dissertation and discuss ongoing and future work.

Cette thèse s'inscrit dans le cadre de la mission spatiale Rosetta et porte sur les propriétés spectrophotométriques de la comète 67P/Churyumov-Gerasimenko à l’aide de l’instrument OSIRIS. Cet instrument est composé de deux caméras pour les observations du noyau et de la coma de la comète. Elles permettent d’acquérir des images avec des filtres qui opèrent dans la gamme du proche UV au proche IR. Dans un premier temps, j'ai analysé les courbes spectrophotométriques des taches claires qui sont apparues sur le noyau de la comète. Une étude comparative de celles-ci grâce aux données du spectro-imageur VIRTIS a ainsi permis de constater que les taches claires sont liées à la glace de H2O. Dans un second temps, j’ai entrepris une étude spectrophotométrique de la région Khonsu, qui a mis en évidence les variations saisonnières de la pente spectrale de différents terrains. Par la suite, j’ai élargi mon analyse des taches à tout le noyau de la comète. J’ai détecté plus de 50 taches claires dues à la présence de glace de H2O et j’ai produit une carte pour repérer leurs emplacements sur le noyau, afin d’étudier plus en détail leur répartition et leur évolution au cours de temps. Ceci m’a permis d’identifier quatre types de taches regroupés en fonction de leur morphologie et de constater qu'elles sont dues à différentes sources d'activité cométaire. / This thesis is based on the spectrophotometric properties of the comet 67P/Churyumov-Gerasimenko, using the OSIRIS instrument of Rosetta space mission. Composed of two scientific cameras to observe the nucleus and the coma of the comet, OSIRIS images are acquired with multiple filters, that span the near-UV to near-IR wavelength range. They were used to study the spectrophotometric curves of the exposed bright features that appeared on the surface of the cometary nucleus, leading to a comparative study, that was carried out in collaboration with the VIRTIS spectro-imager aboard Rosetta, that demonstrated, that these exposures are related to H2O ice, using its absorption band located at 2 microns. The thesis further details a spectrophotometric study of the Khonsu region in the southern latitudes of the comet, where the seasonal variation of the spectral slope of different types of terrains is explored. Finally, the results of an extended survey of exposed bright features are presented. More than 50 individual features are presented under four morphologies along with an albedo calculation, suggesting that different activity sources are responsible for their appearance on the nucleus.

By examining five types of astronomical and celestial phenomena—comets, constellations, the zodiac, planets, and the music of the spheres—this thesis posits not only that early modern dramatists were influenced by established and emerging natural philosophy as habits of thought that manifested in their writing, but also that astronomical phenomena operate within the drama, performance, and in the theatre as elements for creating and developing a distinctly spatial dramaturgy. Using theories from the spatial turn, this thesis maps the positions, edges, disturbances, and motions of celestial properties within the imaginary and physical space of early modern drama and theatre. It argues that the case study plays examined within this thesis demonstrate a period-wide engagement, rather than an authorial-, company-, theatre-, or even genre-specific practice. Dramatists developed techniques using astronomical phenomena as dramatic methods that occasionally underscored early modern astronomical thought. However, in many cases constructed plots, characters, visual and sound effects, and movements transgressed astronomical expectations. Dramatists broke down constellations, inserted new stars in the heavens, created zodiacal females, launched pyrotechnical comets, moved planets unexpectedly across the stage, and played (and refrained from playing) celestial "music" for the audience. Recognising composite and often contradictory astronomical constructions within the drama, this thesis moves the critical discussion away from an intellectual history of natural philosophy and gravitates toward an active astronomical dramaturgy.

Les particules cométaires sont des témoins de l’évolution du système solaire, dont les caractéristiques peuvent être estimées à partir de la lumière qu’elles diffusent et émettent.<p>Je montre qu’un modèle de diffusion lumineuse par un nuage d’agrégats fractals et de sphéroïdes permet d’interpréter, en fonction de la distribution en taille et des matériaux constitutifs, des observations polarimétriques en angle de phase et longueur d'onde. Le modèle est en particulier appliqué à la comète Hale-Bopp, et au milieu interplanétaire en modélisant aussi les observations thermiques.<p>Je développe des outils de diffusion lumineuse (numériques et expérimentaux) pour analyser des agrégats analogues aux particules protoplanétaires qui seront formés avec ICAPS à bord de l’ISS. De façon complémentaire, une simulation expérimentale en vol parabolique avec PROGRA2 me permet de déterminer les propriétés physiques de microparticules d’intérêt astrophysique par des mesures polarimétriques.<p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

This thesis presents an autonomous vision-based navigation strategy applicable to the approach phase of a small body mission, developed within the Robotics Section at NASA Jet Propulsion Laboratory. Today, the operations performed to approach small planetary bodies are largely dependent on ground support and human decision-making, which demand operational complexity and restrict the spectrum of achievable activities throughout the mission. In contrast, the autonomous pipeline presented here could be run onboard, without ground intervention. Using optical data only, the pipeline estimates the target body's rotation, pole, shape, and performs identification and tracking of surface landmarks, for terrain relative navigation. An end-to-end simulation is performed to validate the pipeline, starting from input synthetic images and ending with an orbit determination solution. As a case study, the approach phase of the Rosetta mission is reproduced, and it is concluded that navigation performance is in line with the ground-based state-of-the-art. Such results are presented in detail in the paper attached in the appendix, which presents the pipeline architecture and navigation analysis. This thesis manuscript aims to provide additional context to the appended paper, further describing some implementation details used for the approach simulations. / Detta examensarbete presenterar en strategi för ett autonomt visionsbaserat navigationssystem för att närma sig en liten himlakropp. Strategin har utvecklats av robotikavdelningen vid NASA Jet Propulsion Laboratory i USA. Nuvarande system som används för att närma sig en liten himlakropp bygger till största delen på markstationer och mänskligt beslutsfattande, vilka utgör komplexa rutiner och begränsar spektrumet av möjliga aktiviteter under rymduppdraget. I jämförelse, det autonoma system presenterat i denna rapport är utformat för att köras helt från rymdfarkosten och utan krav på kontakt med markstationer. Genom att använda enbart optisk information uppskattar systemet himlakroppens rotation, poler och form samt genomför en identifiering och spårning av landmärken på himlakroppens yta för relativ terrängnavigering. En simulering har genomförts för att validera det autonoma navigationssystemet. Simuleringen utgick ifrån bilder av himlakroppen och avslutades med en lösning på banbestämningsproblemet. Fasen då rymdfarkosten i ESA:s Rosetta-rymduppdrag närmar sig kometen valdes som fallstudie för simuleringen och slutsatsen från denna fallstudie var att systemets autonoma navigationsprestanda var i linje med toppmoderna system. Den detaljerade beskrivningen av det autonoma systemet och resultaten från studien har presenterats i ett konferensbidrag, som ingår som bilaga till rapporten. Inledningen av rapporten syftar till att förtydliga bakgrunden och implementering som komplement till innehållet i bilagan.

This thesis describes the design, implementation and analysis for a preliminary study for DLR's MASCOT lander's next mission to Small Solar System Bodies (SSSB). MASCOT (Mobile Asteroid Surface Scout) is a nano-lander that flew aboard Hayabusa2 (JAXA) to an asteroid, Ryugu. It is a passive nano-spacecraft that can only be deployed ballistically from a hovering spacecraft. Current research focusses on optimizing similar close-approach missions for deploying landers or small cubesats into periodic orbits but does not provide solutions with semi-autonomous small landers deployed from farther distances. This study aims to overcome this short-coming by proposing novel yet simple Guidance, Navigation and Control (GNC) and Propulsion systems for MASCOT. Due to its independent functioning and customisable anatomy, MASCOT can be adapted for several mission scenarios. In this thesis, a particular case-study is modelled for the HERA (ESA) mission. The first phase of the study involves the design of a landing trajectory to the moon of the Didymos binary asteroid system. For a preliminary analysis, the system - Didymain (primary body), Didymoon (secondary body) and MASCOT (third body) - are modelled as a Planar Circular Restricted Three Body Problem (PCR3BP). The numerical integration methodology used for the trajectory is the variable-step Dormand–Prince (Runge Kutta) ODE-4,5 (Ordinary Differential Equation) solver. The model is built in MATLAB-Simulink (2019a) and refined iteratively by conducting a Monte Carlo analysis using the Sensitivity Analysis Tool. Two models - a thruster-controlled system and an alternative hybrid propulsion system of solar sails and thrusters - are simulated and proven to be feasible. The results show that the stable manifold near Lagrange 2 points proposed by Tardivel et. al. for ballistic landings can still be exploited for distant deployments if a single impulse retro-burn is done at an altitude of 65 m to 210 m above ground with error margins of 50 m in position, 5 cm/s in velocity and 0.1 rad in attitude. The next phase is the conceptual design of a MASCOT-variant with GNC abilities. Based on the constraints and requirements of the flown spacecraft, novel GNC and Propulsion systems are chosen. To identify the overriding factors in using commercial-off-the-shelf (COTS) for MASCOT, a market survey is conducted and the manufacturers of short-listed products are consulted. The final phase of the study is to analyse the proposed equipment in terms of parameter scope and capability-oriented trade-offs. Two traceability matrices, one for devised solutions and system and another for solutions versus capabilities, are constructed. The final proposed system is coherent with the given mass, volume and power constraints. A distant deployment of MASCOT-like landers for in-situ observation is suggested as an advantageous and risk-reducing addition to large spacecraft missions to unknown micro-gravity target bodies. Lastly, the implications of this study and the unique advantages of an enhanced MASCOT lander are explored for currently planned SSSB missions ranging from multiple rendezvous, fly-by or sample-return missions. Concluding, this study lays the foundation for future work on advanced GNC concepts for unconventional spacecraft topology for the highly integrated small landers. / <p>This thesis is submitted as per the requirements for the Spacemaster (Round 13) dual master's degree under the Erasmus Mundus Joint Master's Degree Programme. </p> / MASCOT team, DLR