Modeling, Dynamics and Control of Space Tethered System as Distributed Radar Array

Distributed Space Systems are an anticipated critical technology, thanks to which it would be possible to achieve performance unattainable with classical monolithic satellites. These systems are composed of several small satellites working together to achieve a common goal. Due to the distributed nature of this type of system, it is possible to achieve great reliability and adaptability to different types of missions, providing great robustness and flexibility while maintaining low costs. The purpose of this thesis is to study the dynamics and control of a Tethered Space System: a system composed of several CubeSats connected to each other via a tether. Several other analyses have already been carried out at the Jet Propulsion Laboratory over the past few years, in order to assess the possible applications of this type of architecture in Low Earth Orbit. Among them, the use of a radially positioned tethered system for radar remote sensing is of particular interest: due to the presence of the gravitational gradient, this configuration is particularly stable and performing, preserving the relative position between its elements with a less frequent and expensive control. Therefore, the aim of this work is to continue the research on this type of system, evaluating the reliability of a radial tethered system and considering the feasibility of other possible configurations. To do this, an optimization and improvement of the tool used for the simulation of this type of system was initially carried out, analyzing the significant influence of the integration method on the calculation time required for simulation. As a result of the optimization work carried out, it was possible to perform an Uncertainty Propagation analysis based on Monte Carlo methods, which further revealed the better performance of a Tethered Space System compared to Formation Flight. Finally, the feasibility of an across-track configuration was analyzed, introducing an optimal control and a state estimator to keep the system in place. This analysis revealed that the stabilization of this configuration is relatively simple, requiring only a constant force in modulus and direction. Therefore, the possibility of introducing a control through aerodynamic surfaces to limit the use of the actuators was evaluated.