The objective of the research was to develop the Attitude Control System algorithm to be implemented in the Earth Observation Satellite System composed of leader-follower formation. The main task of the developed Attitude Control System is to execute attitude change manoeuvres required to point the axis of the image acquisition sensor to the fixed target on the Earth’s surface, while the satellite is within the segment of an orbit, where image acquisition is possible. Otherwise, the satellite maintains a nadir orientation. The control strategy is realized by defining the high-level operational modes and control laws to manage the attitude control actuators: magnetorquers used for desaturation of the reaction wheels and reaction wheels used for agile attitude variation. A six-degree-of-freedom satellite model was used to verify whether the developed Attitude Control System based on PID controllers for actuators performs attitude control in line with the requirements of an Earth Observation System. The simulations done for a variety of combinations of orbital parameters and surface target positions proved that the designed Attitude Control System fulfils the mission requirements with sufficient accuracy This high-level architecture supplemented by a more detailed control system model allowed proving efficient functionalities performance.