Low thrust relative orbital transfer uses orbital motion equations (such as the Clohessy-Wiltshire equations that are very useful in planning rendezvous of the chaser with the target, published in 1962) to explain the differences in orbits and displacements of target and chaser spacecraft.
In orbital mechanics, low-thrust relative transfer is an orbital maneuver in which a chaser spacecraft covers a specific relative distance relative to the target spacecraft using continuous low-thrust system with specific impulse of the order of 4000-8000s. In 1960, W. H. Clohessy and R. S. Wiltshire published the Clohessy-Wiltshire equations, which presents a rather simplified model of orbital relative motion, in which the target is in a circular orbit, and the chaser spacecraft is in an elliptical or circular orbit. 
