The performance of the auroral large imagining system (ALIS_4D) and an automatic track detection algorithm was evaluated for space debris surveillance and tracking. The evaluation of the ALIS_4D was done through a numerical simulation and data annotations, while the track detection results were manually evaluated. The effect of auroral conditions, filters, and the detection mode were evaluated for the performance of both.  It was found that  ALIS_4D can detect resident space objects. The peak detection rate per hour was dependent on the time of the year, day, and the limiting magnitude set by the filters and the sensor among others. The peak was simulated to be approximately 120 in January and 70 in April and September. A space object observation campaign was performed in April 2020 for 90 minutes. During that period across the used four stations 61 unique objects were detected and 37 unique objects were detected at the Abisko station, that was used for the simulation. During the observation time there was auroral activity which can block the line-of-sight to resident space objects.  The track detection algorithm was evaluated for data gathered in a dedicated space situational awareness (SSA) mode and other modes. In SSA mode, the algorithm found 60% of the subsections of the image with visible traces. The false detection rate was 17% when no auroras were present and 56% when there were. In other modes the evaluation was simplified due to large number of false positives. When assumed best case scenario 99.2% of the detections were false. The auroral activity and the used mode had the most significant effect on the track detection algorithm performance. It was found that in SSA mode the used filter did not effect on the track detection performance.

Afin de mieux estimer la survivabilité des débris spatiaux lorsqu’ils retombent sur Terre (masse finale et surface meurtrie), la base de données matériaux du code DEBRISK du CNES nécessite d’être alimentée en propriétés dans le domaine des hautes températures (oxydation et émissivité principalement). Ainsi, cette thèse a été réalisée au laboratoire PROMES-CNRS sur l’étude expérimentale de l’oxydation dans des conditions de rentrée atmosphérique (plasma d’air, haute température et basse pression) de quatre alliages métalliques les plus difficiles à détruire (Invar 36, TA6V, 316L et 304L). L’émissivité totale directionnelle a également été mesurée à haute température et l’émissivité totale hémisphérique a été calculée pour ces quatrematériaux, sur des surfaces non oxydées, sous vide secondaire, mais aussi, pré-oxydées sous plasma d’air et oxydées in situ sous air standard. Les résultats ont montré pour l’ensemble des matériaux, que l’oxydation à haute température sous environnement d’oxygène atomique, était peu significative vis-à-vis des faibles gains ou pertes de masse obtenus (dépendant de l’alliage) par rapport aux masses initiales. Par contre, l’oxydation crée une forte modification de la surface – composition et morphologie – ce qui entraine une importante augmentation d’un facteur 3 voire 4 (dépendant de l’alliage) de l’émissivité totale des matériaux oxydés par rapport à celle des échantillons vierges, cette augmentation pouvant fortement retarder le processus de fusion pendant une trajectoire et par conséquent le calcul de la masse finale et de la surface meurtrie. De plus, il a été observé que l’émissivité des oxydes formés sous plasma d’air était généralement 10% supérieure à celles des oxydes formés sous air standard, d’où l’intérêt de mesurer l’émissivité sur des surfaces préalablement oxydées sous plasma d’air, caractéristique des conditions de rentrée atmosphérique des débris spatiaux. Finalement, il apparait plus judicieux d’implémenter dans les codes de rentrée atmosphérique, l’influence de l’oxydation sous plasma d’air sur l’émissivité plutôt que les cinétiques d’oxydation obtenues. / To better assess the survivability of space debris when they fall at ground (final mass and casualty area), the DEBRISK tool from CNES needs to feed its material database with properties at high temperatures (oxidation and emissivity mainly). Thus, this thesis was conducted at the PROMES-CNRS laboratory on the experimental study of oxidation in atmospheric re-entry conditions (air plasma, high temperature and low pressure) for four metallic alloys which are the most difficult to destroy (Invar 36, TA6V, 316L and 304L).The total directional emissivity was measured at high temperature for all the materials and the totalhemispherical emissivity calculated, on non-oxidized samples, in high vacuum, but also, on pre-oxidized samples under air plasma and on in situ oxidized ones in standard air. The experimental results have shown for all the materials that the oxidation at high temperature under air plasma was not significant, due to the obtaining of small mass gains or losses (depending of the alloy) compared to the initial masses. However, oxidation creates a huge modification of the surface – composition and morphology – that leads to a significant increase of the total emissivity of oxidized materials compared to the one of virgin samples by a factor 3 or even 4 (depending on the alloy) that can strongly delay the melting process during a trajectory andconsequently the calculation of the final mass and the casualty area. Moreover, it was observed that the emissivity of oxides formed under air plasma was generally 10% higher than those formed in air standard, hence the interest to perform emissivity measurements on pre-oxidized samples under air plasma conditions, representative of the atmospheric re-entry conditions of space debris. Finally, it would be more judicious to implement in the atmospheric reentry tools, the influence of the oxidation under air plasma on the emissivity rather than the kinetics of oxidation obtained.

This Ph.D. thesis is devoted to the development of a specific semi-analytical algorithm especially well-suited to derive the long-term evolution of near geosynchronous space debris and based on the concept of mean orbital motion. In a first approach, the semi-analytical theory is concerned with the singularity issues arising for circular and equatorial orbits as well as with the geostationary resonance modeling. In a second part, motivated by the discovery of high area-to-mass ratios space debris in high altitude Earth's orbit (mostly near the geosynchronous region), the direct radiation pressure models are revisited and completed. Within this context, the main effects of the direct solar radiation pressure for the mid- and long-term evolution of both the eccentricity and the inclination vectors are analyzed through a well-suited model. Moreover, by means of a smart extension, the passage in the Earth's shadow is taken into account in the computations of the orbits. Finally, a further insight into the intrinsic stability of such space debris is performed, by means of a recent numerical technique (MEGNO) which is based on the concept of ``variational chaos indicator'.

Les débris spatiaux constituent une menace pour l'exploration et l'exploitation de l'espace. Leur nombre ne cesse d'augmenter et continuera à grandir même si on arrête toute activité spatiale, augmentant ainsi la probabilité d'entrer en collision avec un satellite actif. Le retrait des débris s'avère le seul moyen de protéger ces satellites. Le nombre des débris spatiaux étant très élevé, il convient préalablement de repérer les plus dangereux.Dans la première partie de la thèse, nous avons élaboré une approche multicritère afin de classer les débris selon leur degré de priorité d'enlèvement. Les débris de la classe la plus prioritaire, feront l'objet d'une mission spatiale de retrait de débris.La planification d'une telle mission est étudiée dans la deuxième partie de la thèse. Elle doit être réalisée en minimisant deux critères : le coût de la mission ainsi que la durée nécessaire pour traiter tous les débris. / Space debris are a threat for the space exploitation and exploration. Their number will continue to increase even if we stop all space activities, making collisions between debris and operational satellites more likely to happen. Debris removal proves necessary to protect active satellites. Since the number of space debris is very high, we should first deal with the most dangerous ones.In the first part of this thesis, we have developed a multicriteria approach to categorize debris depending on their removal priority degree. Debris belonging to the most urgent category will be dealt with during a space mission. The planning of such a space mission is studied in the second part of this thesis.The planning should be designed while optimizing two criteria: mission cost and mission duration.

In Space Situational Awareness (SSA), it is crucial to assess the uncertainty related to thestate vector of resident space objects (RSO). This uncertainty plays a fundamental role in, forexample, collision risk assessment and re-entry predictions. A realistic characterization of thisuncertainty is, therefore, necessary.The most common representation of orbital uncertainty is through a Gaussian (or normal)distribution. However, in the absence of new observations, the uncertainty grows over timeand the Gaussian representation is no longer valid under nonlinear dynamics like spacemechanics. This study evaluates the time when the uncertainty starts becoming non-Gaussianin nature. Different algorithms for evaluating the normality of a distribution were implemented andMonte Carlo tests were performed on them to assess their performance. Also, the distancesbetween distributions when they are propagated under linear and nonlinear algorithms werecomputed and compared to the results from the Monte Carlo statistics tests in order to predictthe time when the Gaussianity of the distribution breaks. Uncertainty propagation using StateTransition Tensors and Unscented Transform methods were also studied. Among theimplemented algorithms for evaluating the normality of a distribution, it was found thatRoyston’s method gives the best performance. It was also found that if the Normalized L 2distance between the linear and non-linear propagated distributions is greater than 95%, thenuncertainty starts to become non-Gaussian. In the best case scenario of unperturbed two-bodymotion, it is observed that the Gaussianity is preserved for at least three orbital periods in thecase of Low-Earth and Geostationary orbits when initial uncertainty corresponds to the meanprecision of the space debris catalog. If the initial variances are reduced, then Gaussianity ispreserved for a longer period of time. Time for which Gaussian assumption is valid on orbitaluncertainty is also dependent on the initial mean anomaly. Effect of coordinatestransformation on Gaussianity validity time is also analyzed by considering uncertainty inCartesian, Keplerian and Poincaré coordinate systems. This study can therefore be used to improve space debris cataloguing.

En 1957, la conquête de l'espace par l'homme commença avec le succès de la mise en orbite du premier satellite artificiel ; Spoutnik 1. Ce fut le début de l'exploitation de l'orbite terrestre caractérisée par une centaine de lancements de fusées partant de Kourou, Baïkonour et autres bases de lancement. Aujourd'hui, l'orbite terrestre a une population composée en majeure partie de débris spatiaux. Ces derniers regroupent des étages supérieurs de fusée, des satellites ayant fini leur mission et autre petits objets artificiels dont l'origine n'est pas forcément identifiable. Leur nombre est devenu si important, allant même jusqu'à remettre en cause la viabilité des activités spatiales que leur étude est devenu incontournable. La génération de nouveaux débris se traduit majoritairement par l'avènement d'une collision ou d'une explosion. Une meilleure connaissance de ces évènements dits évènements de fragmentation permettra une meilleure lutte contre la prolifération des débris spatiaux. Afin d'optimiser l'étude d'un nuage de débris, il est nécessaire de développer de nouveaux outils. Dans la première partie de la thèse, nous élaborons un modèle de fragmentation permettant de créer des nuages de débris spatiaux générés à la suite d'une explosion ou d'une collision. Pour cela, nous partons du modèle de fragmentation de la NASA, Evolve ainsi que d'autres fonctions de distribution issus de diverses expériences de fragmentation. Grâce à ce modèle, nous obtenons des paramètres géométriques et également en termes de vitesse dont nous chercherons à déterminer leur influence sur le mouvement du nuage. / In 1957, the space conquest by man began with the successful launch into orbit of the first artificial satellite; Sputnik 1. This was the beginning of the exploitation of the earth's orbit characterized by a hundred of rocket launches starting from several launchpad such as Kourou or Baikonur. Today, the Earth's orbit has a population composed mostly of space debris. These include upper rocket stages, satellites which have ended their mission and other small artificial objects whose origin is not necessarily recognizable. Their number has become so important that it question the sustainability of space activities. In this thesis we figure out the difficulties to handle the issue posed by the space debris. In the first part of the thesis, we develop a fragmentation model to generate clouds of space debris as a result of an explosion or collision in space. For this, we mainly used the fragmentation model of NASA, Evolve, and other distribution functions from diverse experiences of fragmentation. Thanks to this model, we know the geometric parameters and also in terms of speed which we will seek to determine their influence on the movement of the cloud. Thus, in the second part of the thesis, we study the motion of space debris evolving initially in low Earth orbit.

The thesis considered the feasibility of space warfare with an emphasis on the malicious potential of dual-use technology. I have described the orbital principles and set the presumptions of space warfare and the principles for space warfare strategy, introduced dual- use technology and its connections to space weapons, elaborated on existing counterspace capabilities and its impact, described the challenges for space warfare and evaluated the utilization of dual-use technology as space weapons. I have reached the conclusion that current space technology does not allow to lead extensive space warfare. However, counterspace technology is mature enough for the conduct of destructive space operations and states are encouraged to proliferate advanced offensive counterspace capabilities that are not sufficiently addressed and bounded to international law. Though, despite it seems space warfare is unlikely, the growing tensions of state space actors and rapid development of new technology that is currently mostly driven by the commercial actors may soon change the situation. Potentially destructive dual-use technology may then increase the risk and probability of space warfare. The thesis proposed several options of potentially destructive dual-technology technology that could be turned into space weapons.

<div>With the increasing frequency of satellite launches and proposed constellations for Earth observation and communications, the number of objects in orbit is expected to increase significantly in the coming decades. This trend brings to question the current orbital debris problem, which will continue to worsen if proper deorbit guidelines are not met for future satellites. Currently, the primary system that is utilized for deorbiting is a propulsion system that performs a maneuver at the end of mission and delivers the satellite on an orbit that satisfies deorbit guidelines. However, this method suffers from reliability concerns since it requires that the host spacecraft be operational to perform the maneuver and it also significantly increases the cost and complexity of the satellite if a propulsion system is not already being used for the mission. These issues with complexity, cost, and robustness could potentially be solved by a different class of deorbiting system, a drag sail.</div><div><br></div><div>In this thesis, the effects of perturbations on the orbital and attitude motion of drag sails are analyzed in order to extend the current understanding of drag sails as a deorbiting system. The perturbations considered in the orbit-attitude propagator are aerodynamic drag, solar radiation pressure, Earth oblateness effects, and gravity gradient torques. Different drag sail types, sail materials, deployment epochs, and deployment locations in Earth orbit are also considered in order to extend the analysis to different types of missions and to understand how these parameters influence the effects of the perturbations. Additionally, a self-shadowing algorithm and efficient implementation approach is developed in order to improve the fidelity of the aerodynamic drag and solar radiation pressure perturbations.</div>

<div><div><div><p>The exponential growth of space debris poses a significant threat to humankind’s activities in orbit. It is thus worthwhile to investigate debris-generating events and uncover their causes, consequently informing debris-mitigation guidelines and safer spacecraft design. This work sets out to examine three fragmentation events pertaining to Centaur upper stages which have yet to be fully understood. Critical breakup characteristics such as breakup epoch, fragment velocities, and angular distributions for the Centaur events, as well as select historic fragmentation events are presented. Subsequently, hypotheses regarding the causes of the events are postulated. The Centaur fragmentations stray from breakup patterns exhibited by ’typical’ upper stage fragmentations such as those of the historic explosive Delta upper stage events. Only one of the three events, 2018-079B, appears to have fragmented due to the combustion of leftover propellant. 2009-047B, on the other hand, likely endured a structural failure – inferred from clustered fragments and low fragment spreading speeds. A torus-shaped fragment distribution is observed for the 2014-055B event, suggesting a collision with a small piece of debris may have taken place.</p></div></div></div>

Magister Legum - LLM / Environmental Law is at the forefront of the global community and environmental protection and conservation is regarded as of the utmost importance.1 Outer Space is a unique, limited, and valuable resource. Outer space allows states to utilise thousands of satellites for research, national defence, and communications. At the inception of space law, only a few states dominated space activities and all human space activities were so challenging that nearly any method seemed acceptable for placing objects in outer space, currently more countries have space industries and launch capabilities