If you want to have a missile track and hit a target, Proportional Navigation is a common technique.
But that's simple intercept and collision, getting the pursuer to the same X, Y, Z as the target.
But how about when you want to rendezvous with the target? Two vehicles with arbitrary vectors, the target on a stable (i.e. not trying to evade, but not necessarily straight) course, what techniques are folks using directing the pursuer to match the position, velocity, and heading of the target?
I think this is a different problem from station keeping or flocking (where the two vehicle are already close), but maybe not.
