Geometric Approach to Spacecraft Attitude Control Using Magnetic and Mechanical Actuation

IT IS well known that spacecraft in low Earth orbit can generate control torques via the interaction of the Earth's geomagnetic field and onboard magnetic dipole moments (created via current-carrying coils) [1,2]. As mentioned in [3], the major shortcoming of magnetic actuation (as the only onboard actuator) is that control torques can only be applied to the spacecraft in a plane orthogonal to the instantaneous direction of the Earth's magnetic field, which in turn means that the spacecraft is instantaneously underactuated.