DYNAMICS AND MOTION CONTROL OF CHALLENGING DISTRIBUTED ORBITAL SYSTEMS
Development and implementation of distributed orbital systems like Formation Flying (formation) based on miniature satellites has become an intensively expanded idea of the previous decade in space exploration. It is an innovation trend of the beginning decade while the idea is transferred to the implementation. Such a trend demands a groundwork and knowledge gathering, design of mission scenarios, development of mathematical models, control algorithms, methods of their verification including laboratory testing. Formation consists of a several satellites moving in nearby orbits and usually in rather short distances to each other in order to solve a common task which demands coordination and maintenance of a relative motion. To analyze satellite dynamics, some specific models of a relative motion taking into account short relative distance are required. The paper considers various models of the satellite relative motion staring from elementary one like the Hill − Clohessy − Wiltshire model which describes the relative motion of one satellite relatively another in a central Newtonian gravitational field in a linear approximation. The latter satellite moves in a circular orbit. If satellites move outside of the atmosphere the main factor affecting their motion is the oblateness of the Earth which generates a secular effect in a divergence of satellites originally moving in the vicinity of each other. For approximation description of the relative motion in presence of the Earth oblateness with the J2 harmonic of the potential expansion the Schweighart − Sedwick equations can be used. While a formation is designed two main problems are to be solved. The first one is to develop it in the orbit and the second one is to maintain the formation for a whole time of its activity. Development scheme depends on a maneuvering strategy and orbiting approach used to launch satellites in orbit. Maintenance of the formation based on orbital motion control links close to the problem of formation orbits evolution interesting from the celestial mechanics point of view. In the paper the formation default configurations are given with the main factors which affect their evolution. Technique to maintain a formation is considered including elementary algorithms of orbital motion control with approaches to verify them numerically and using laboratory testing. A few samples of realized and designed formation missions are given with their purposes and tasks which have to be solved and also with features in their dynamics.