ABSTRACT
There are typical situations in the dynamics of space systems when small disturbances act on the system in addition to the main forces and moments [121]. Such situations occur both for orbital motions and for many cases of motion around the mass centre in the task of orientation and stabilisation of the motion of space systems. In unperturbed motion due to the design of the mechanical system the main regular properties of the motion are known. The smallness of disturbances guarantees that on a small time interval the perturbed motion differs only little from the unperturbed one. Long-term effects of perturbing forces can result in accumulation of disturbances in the motion of a system and essentially change its characteristics in comparison with the unperturbed motion. Therefore the main purpose of research of perturbed motions is the research of changes of characteristics of motion over a long time interval and the determination of regular features of its evolution.
