Because all of it is expected and known. It would actually be a lot harder to calculate if it were something taking place just here on earth. You have to factor in stuff like wind and turbulence which throws calculations off. But in space? Little to no unexpected variables. It’s Newton’s first law; an object in motion stays in motion.
We know the position of the moon and how it will move.
We know the position of the earth and how it will move.
We know the position of the spacecraft and how it will move.
From there, it’s just math.
yogurt@lemmy.world 2 days ago
The real answer is you can’t, every time the astronauts take a piss it’s throwing everything off. But they do know where San Diego is going to be, and they want to land the capsule off the coast of San Diego, so they keep making adjustments throughout the flight so they stay on course to hit the water at 8:07:27 because that’s when San Diego is going to be there.