Rest assured your mining fleet will not be attacked or intercepted by other fleets however, rewards are mediocre compared to the other planets.
Be warned, there are pirate NPCs that will appear, albeit from time to time, and this can pose a threat to your fleet. Income rewards on Low Risk planets are much higher than safe planets.
If you’re as brave as you are lucky, the High risk planet will offer players much higher income opportunities than the previous two. But this does not come without risks! Players will have to deal with pirate NPCs and other fleets intercepting their barges.