Why doesnt the drag free control cause the helium to slosh?
The drag free control actually prevents the helium sloshing. It causes the satellite to follow an inertial trajectory in spite of disturbances, that is, the same trajectory that it would follow if there were no disturbances at all. The helium, contained in the satellite, also follows the trajectory it would follow without disturbances. If something caused the helium to slosh, the helium moving back and forth would push against the satellite and disturb it. The drag free control would react to this disturbance by preventing the satellite from moving. Since the feedback is stable, this always reduces the heliums motion.
