Position trackers are cool, but currently only work with directional sensor. For the sake of better implementation and to allow for more complex/interesting drones, have the altitude meter also able to track position trackers. Lower bounds of an altimeter can be the planetary/gravity center of a planet, while you could either set upper or middle bounds of the altimeter to the position tracker. This way, you can dynamically change the altimeter's "sweet spot" mid planet exploration without having to leave planet, edit drone, then edit altimeter manually. I also believe this will allow for a lot of possible orbiting designs that can be used on planets with any shape without worry of missing or crashing into the resource collector drone.