How does space scientist predict a course of route for a satellite?

Adop would be better than predict. Keeping in view that there must be many asteroids, comets etc which are not visible from Earth. Then how they know which path/route etc to follow to avoid even minute of alien particles? For example some satellites have gone as far as Saturn and Jupiter avoiding even a tiny bit of space rock etc. And at that speed even a pebble would seem an Everest. Is it luck or real precise navigation, information and calibration?