This thesis focuses on the development of the Attitude Determination and Control System (ADCS) for a tethered satellite system, with the main objective of demonstrating that tether-induced torques can be effectively exploited as external actuation for spacecraft attitude control. The system under consideration consists of two SmallSats connected by a flexible tether; this configuration is particularly promising, as it enables new mission configurations that would otherwise be impractical or infeasible, particularly for multi-angle Earth Observation applications. Such missions demand high pointing accuracy, while the presence of the tether introduces strong dynamic coupling between the attitude dynamics and the tether tension, significantly increasing the complexity of the attitude control problem.