LEO satellites can utilize the Earths magnetic fields of flux to maintain pointing in 2 of the 3 axis by employing Magnetic Torque Coils, also called Torque Rods.

Since these coils are electromagnets one end of the coil will be positive (North) and other end will be negative (South). These coils are aligned with the axis to be controlled and energized to produce a magnetic field that will attract it to or repel it from the Earth’s lines of magnetic flux. To actively control the torque from these coils the ADACS system regulates the amount of current, it can be increased or decreased and the direction of current flow can be reversed to change the polarity of the magnetic field being generated. ADACS calculates the pointing errors in each axis, converts it to the required current and applies it to the coil to generate torque to correct the errors.  The ADACS system will de-energize them as the satellite passes over the North or South pole, reverse the polarization and re-energize them as required.  During the brief time the coils are de-energized the momentum of the satellite will allow it to maintain it’s pointing.

Very precise pointing can be achieved by the use of a combination of Reaction Wheels and Magnetic Torque Coils.