Precise Attitude Control Design of a Flexible Spacecraft in Mars Environment

During the last years, the idea of deployable structures is becoming more and more attractive in the space industry. Several missions are influenced by this concept, some application examples are solar sailing, LEO (Low Earth Orbit) deorbiting missions and solar power generation. This design approach has been promoted by technological improvements such as thin film solar cells, new deployment methods, and the miniaturization of satellites. The structure deployment after the launch allows to save a not negligible volume in the launcher. The miniaturization of the spacecraft components and, consequently, of the spacecraft themselves, is bringing a lot of advantages especially from an economic point of view. However, this trend has some weakness: the satellites characterized by a small size are more susceptible to the external disturbances. This trouble become even more serious if the coupling between the main body of the satellite and the flexible appendages is considered. The purpose of this Thesis is to achieve a precise attitude control for a small satellite using reaction wheels as actuators. The small size of the spacecraft and the coupling between the main body of the satellite and the flexible appendages are critical conditions for the management of external disturbances. Two control techniques are employed: Linear Quadratic Regulator and H-infinity. Several mission phases and manoeuvres have been evaluated to test the effectiveness of the controllers. Humanity may need to become a multiplanetary species in the future. Mars seems to be the main candidate to become our second home, thanks to the relatively short distance from the Earth and the acceptable atmospheric conditions. However, before to start a travel towards Mars, it is necessary to collect an enormous amount of information. In addition, this planet is attractive for a list of scientific studies, starting with the research of life outside the Earth. For all this reasons, the number and the complexity of the future missions heading to Mars are expected to grow and the external disturbances for the present work are modelled on the environment of the Red Planet.