Typically, a spacecraft will have reaction wheels or CMGs to generate internal torques which let you change attitude by the conservation of angular momentum. H

Typically, a spacecraft will have reaction wheels or CMGs to generate internal torques which let you change attitude by the conservation of angular momentum. However, there are also external torques in the system. In low Earth orbit, you get atmospheric drag. Solar radiation pressure also affects spacecraft. To overcome this saturation or buildup of momentum in wheels, you need to generate an external torque. This can be done with torque rods that work against Earth's magnetic field. But such a strategy does not work in deep space with no magnetic field, so you would need to use thrusters instead. You typically try to keep your nagnetometer far from torque rods and wheels. Voyager had a huge boom to keep the magnetometer far from the spacecraft I believe. Not sure how you get good separation at femtosat distances.