Magnetorquer

A magnetorquer is an attitude control actuator consisting of a wire coil (or coils wound around a ferromagnetic core) that, when energised, creates a magnetic dipole. This dipole interacts with Earth's magnetic field to produce a torque on the satellite. Magnetorquers are low-power, lightweight, and have no moving parts, making them highly reliable. Their primary limitation is that they can only produce torque perpendicular to the local magnetic field vector, so they cannot control all three axes simultaneously. They are commonly used on small satellites and CubeSats for coarse pointing, and on larger satellites specifically for reaction wheel momentum dumping.