Yup, early in my career I worked in the group, at the JHU/APL, that did the satellite location calculations for the Navy's version of GPS. One of the research

Yup, early in my career I worked in the group, at the JHU/APL, that did the satellite location calculations for the Navy's version of GPS. One of the research projects to help with this, actually in effect to have carefully controlled orbits, was a "drag free" satellite. Basically just put the satellite in a ball. Then the ball still has drag, but the satellite does not. Sure, soon as the satellite without drag moves with respect to the ball that does, have to tweak the orbit of the ball to keep the drag free satellite at the center of the ball.