http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion#Generality
http://en.wikipedia.org/wiki/Kepler_orbit
http://en.wikipedia.org/wiki/Ellipse
the minimum is the radius of the object.
the maximum is the shortest distance we should keep.
what are the minimum moves to get and stay in that range..
can also figure out (calculate) where you meet or almost meet.
if it's moving away from you or towards you, speed, lap time.. u can either "chase" it, or "run away" from it, if you're on the same orbit.
if can't calculate a linear direction for meeting, set course to its previous position, like a triangle, and adjust that every time, or go below its orbit if it's too fast.