Each piece of hardware in space is tracked so space commands know where all things are located. They have to have this when they launch other satellites into space, otherwise, things would be bumping into each other up there.
As far as I understand it, they have to do it in two different ways.
The easiest to track are the ones orbiting the Earth, as they are either visible or detectable by radar or other means, but the ones orbiting the Sun have to be treated like asteroids: they calculate their orbits and check on them when they are close enough.