Spacecraft attitude stabilization using magnetorquers with separation between measurement and actuation

SPACECRAFT attitude control can be obtained by adopting several actuation mechanisms. Among them, electromagnetic actuators are widely used for generation of attitude control torques on satellites flying in low Earth orbits. They consist of planar currentdriven coils rigidly placed on the spacecraft typically along three orthogonal axes, and they operate on the basis of the interaction between the magnetic dipole moment generated by those coils and the Earth’s magnetic field; in fact, the interaction with the Earth’s field generates a torque that attempts to align the total magnetic dipole moment in the direction of the field. Magnetic actuators, also known as magnetorquers, have the important limitation that control torque is constrained to belong to the plane orthogonal to the Earth’s magnetic field. As a result, usually a different type of actuator accompanies magnetorquers to provide full three-axis control; moreover, magnetorquers are often used for angular momentum dumping when reaction or momentum-bias wheels are employed for accurate attitude control.