Geometric aspects of polar and near polar circular orbits for the use of intersatellite links for global communication

Abstract

In this paper the polar and the near polar circular orbit constellations are examined for the use of intersatellite links. We have the following definitions: the polar orbit has an inclination angle of exactly 90 deg and the near polar orbit constellation has an inclination angle between 80 deg and 100 deg but not equal to 90 deg. We present the exact equations for the intersatellite distance, the azimuth and elevation angles between two satellites. These equations are applied to an example system, a system that is using intersatellite links and that is based on the circular polar and near polar orbit constellation. To establish an intersatellite link, the distance between two satellites should be small and the variation of the azimuth and elevation angle should also be small. It is shown how a change of the inclination angle influences the whole orbit constellation in order to provide full coverage of the Earth and it is shown how the inclination angle between two satellites on adjacent orbital planes influences the distance, the azimuth, and the elevation angle difference.