An on-orbit servicing spacecraft includes an engagement system to engage a space vehicle or object to be serviced or tugged, so as to form a space system, and an electronic reaction control system to cause the spacecraft to rotate about roll, yaw, and pitch axes to control attitude and displacement along given trajectories to cause the spacecraft to carry out given maneuvers. The electronic reaction control system includes (i) a sensory system to directly sense physical quantities or allow physical quantities to be indirectly computed based on sensed physical quantities, including one or more of position, attitude, angular rates, available fuel, geometrical features, and on-board systems state, (ii) attitude control thrusters mounted so as to allow their positions and orientations to be adjustable, and (iii) an attitude control computer in communication with the sensory system and the attitude control thrusters and programmed to receive data from the sensory system and to control, based on the received data, positions, orientations, and operating states of the attitude control thrusters so as to control attitude and position of the spacecraft. The attitude control computer is programmed to cause the spacecraft to carry out a given mission including an engagement step, in which the engagement system and the attitude control thrusters are controlled by the attitude control computer to engage a space vehicle or object to be serviced or tugged, and one or more operating steps, in each of which the attitude control thrusters are controlled by the attitude control computer to meet one or more requirements established for the operating step.

In an orbital attitude control device (1150), an ideal thrust axis direction calculator (1505) calculates an ideal thrust axis direction based on information of a predetermined orbit, an ideal attitude calculator (1506) calculates an ideal attitude of the satellite based on the ideal thrust axis direction and a solar direction, and a control torque calculator (1510) calculates an ideal control torque that makes the attitude of the satellite follow the ideal attitude and a torque restraint plane in which the solar direction is orthogonal to a rotational axis of the solar array panel, defines an evaluation function obtained by weighting a distance from the ideal control torque and a distance from the torque restraint plane and then summing the weighted distances, and calculates the control torque that allows the drive constraint to be satisfied and the evaluation function to be minimized.

This patent presents an attitude determination and control system based on a Quaternion Kalman Filter (QKF) with an extendable number of sensors and actuators. Furthermore, it is compatible with the spherical motor as its attitude actuator. The system includes a processor with a QKF, at least one direct attitude actuator, and at least two environmental sensors. Firstly, system dynamics calculates a first propagation attitude determination result. Next, update the first propagation with the attitude sensor measurements. Then, control the satellite's attitude via the attitude actuator closer to the attitude command provided by the user. The proposed system dynamic model could adjust the number of actuators and sensors freely without reprogramming the algorithms for new missions with new configurations on the actuators and sensors. Moreover, if some components fail, the algorithm can automatically remove those related sequences to avoid the overall failure of the system.