Detumbling and reorienting underactuated rigid spacecraft

Underactuated spacecraft can be detumbled using a variable structure controller. The algorithm converges to a sliding surface on which exponential decay of the angular velocities occurs. Lower maximum torque magnitudes results in slower convergence to the sliding surface. Once the spacecraft is at rest, a series of at most three rotations about the two active axes is used to reorient the spacecraft. Simple linear controllers can be used for the reorientation maneuvers.