In the last decades a lot of attention has been dedicated to spacecraft formation flying, i.e., the proximity flight of multiple satellites. As a matter of fact, many possible application of this technology can be found in literature, such as interferometry or ground-track observations. For these reasons, a large amount of research has been dedicated to both theoretical and practical aspects of spacecraft formation flying. The main challenge for formation flying is the control of the configuration maintaining a specific relative distance between the satellites. In order to work as a collective, the individuals must be kept in close proximity by reducing their relative drift, while minimizing the fuel expenditure.