In the present paper, which was written in collaboration with the Observatory of Paris, thermal models of two CubeSat missions were created. The first goal of this work was to create a nodal simulation of the PicSat satellite to verify the survivability of the system within the extreme space environment. In a second step suitable countermeasures were suggested, if parts of the satellite exceeded a critical temperature limit. Additionally, the impacts of three failure modes were investigated. The second goal was to perform thermal pre-studies of different satellite configurations of the CIRCUS satellite based on the model of PicSat. The simulation conducted in this work showed that PicSat fulfils its thermal requirements, except for three components. Out of the failure modes considered in this study, only an error of the attitude determination and control systems (ADCS) showed a critical impact on the thermal state of PicSat. As the outcome of the pre-studies of CIRCUS, two of the considered configurations were recommended for further analysis. The results of this work will contribute to the future development of the PicSat and CIRCUS missions. / Dans le cadre de ce mémoire, qui a été rédigé en collaboration avec l'Observatoire de Paris, les modèles thermiques de deux missions CubeSat ont été créés. Le premier objectif de ce projet était de d\'velopper une simulation nodale du satellite PicSat afin de vérifier la capacité de survie du système dans les conditions hostiles de l'espace. Dans un second temps, des mesures correctives ont été suggérées si la température de certaines sections du satellite venait à excéder une limite critique. En outre, les impacts de trois défaillances ont été analysés. Le second objectif était de réaliser des pré-études thermiques pour différentes configurations du satellite CIRCUS basées sur le modèle de PicSat. Les simulations réalisées dans le cadre de ce projet ont montré que PicSat remplit ses exigences thermiques, à l'exception de trois composants. Des différentes défaillances étudiées, seule une erreur du système de détermination et de contrôle d'attitude (Attitude Determination and Control System ADCS) a montré un impact critique sur l'état thermique de PicSat. A l'issue des pré-études de CIRCUS, deux des configurations étudiées ont été recommandées pour être l'objet d'une analyse plus avancée. Les résultats de ce projet contribueront au développement à venir des missions des satellites PicSat et CIRCUS.

The Swedish Institute of Space Physics (IRF) at Kiruna focuses on research activities in the ionosphere, magnetosphere, and upper atmosphere of the planet as well as the development and production of various sensors and detectors for space research. The test facility includes the IRF SpaceLab which is equipped with multiple testing equipment. One of the testing resources available is the Solar Simulator, which consists of a vacuum chamber equipped with four metal halide lamps that produce a spectrum closely resembling that of the Sun. When any spacecraft payload or instrument is exposed to the Sun and its radiations, the most important factors to consider are the type of radiation, flux, and how the exposed material will react. Thermal designing and solar balance tests are important factors in achieving expected conditions for different missions. By testing and verifying these lamps, this solar simulator can be used not only for IRF missions but also for other institutes and private organizations that can access it. The characterization of four lamps is done in terms of temperature distribution, radiation, and power. According to preliminary experimental measured values obtained from the setup, exposed material, and its properties can be varied and the best suitable coating can be selected that includes α (absorptivity) and ϵ (emissivity) valueconsideration. The thesis is divided into four phases: Designing, Manufacturing, Testing, and Analyzing. Before entering into these phases, the basic knowledge of thermal engineering and thermal simulation is acquired. Thermal modeling and simulations are done in Airbus Defence & Space’s Systema Thermica software tool. The design phase includes designing a frame structure and a 350 x 350 mm screen in Autodesk Inventor software. Manufacturing of the frame structure and the screen was done in the IRF workshop. This screen kept hanging with the support of a frame structure which is mounted on the copper table inside the chamber. The screen is kept in the field of view of each lamp and every lamp is illuminated accordingly. The analysis is done by measuring the temperature of the back side of the screen. Temperature sensors were mounted and clamped mechanically instead of kapton tape to avoid direct contact with the screen. The obtained values are analyzed and compared with the thermally simulated values. Pressure and the temperature of the system were monitored with independent systems throughout the test procedure. This thesis report could operate as a foundation for future examination of the solar simulator’s lamps in order to determine precise efficiency.