Polar elliptic orbits for global coverage constellations

In the growing amount of work about satellite constellations ensuring global coverage, orbits are usually assumed as circular. Eccentricity, which destroys the simmetry of the constellation, is then considered as a parameter to be vanished. Nevertheless, it seems to be interesting to study the case of elliptical orbits for LEO constellations; as a first point, it completes and enlarges previous analysis for circular case; on the other side, it could offer some advantages, for example with respect to the single, specific satellite avalaibility from a fixed station. In this paper, accent is given to the geometric criteria to determine the configuration of the constellation, with respect to a classical analysis method (the street of cowrage), extended here to elliptic case. It is shown that this approach, basicly analytical, becomes numerical when applied to the elliptic case. Some results are also presented, in order to indicate the direction to further studies. Finally, considerations about the effect of the perturbations and :he orbital control needed in order to satisfy coverage requirements are reported.