On the concept of periapsis in Hill's problem (Q1766256)

The authors consider the Hill's problem, i.e. investigate the relative motion of two small masses gravitationally interacting with each other and perturbed by a large distant body (as it first was formulated by Hill for Moon, Earth and Sun). A concept of the closest approach is analyzed resulting in a partitioning of the position space (the libration point region, the region of asymptotic variations of quasi-circular orbits, the low energy escape region, the capture region etc.).