Something struck me as confusing, and I'm sure it's just that I don't have enough information yet. The Voyager mission found MANY surprises in the planets they studied. In fact, it seems they were wrong about more than they were right about, not to mention all they found out that they simply did not consider before. What is confusing to me is that they planned this intricate and precise trajectory employing gravity assist while knowing so little about the planets, including geological makeup. Hell, they STILL don't know how deep the clouds are on Jupiter and know nothing at all about the central mass (if there even IS one). Lacking all this information, how did they know how far and fast the planets would "sling" the Voyagers? The measurements had to be extremely precise to get it right, where did they get the numbers? How did they know how much gravitational force Saturn would exert on the crafts? How did they avoid debris and moons that were so far that they did not even know they existed at the time? With all fuel burned up early in the voyage, how did they change the trajectory mid-course like they did to pass over the north pole of Neptune?