Examination of the circular polar satellite constellation for the use of intersatellite links

In the next few years, a new generation of mobile satellite systems (MSS) will be available. These systems will use satellites on low Earth orbits (LEO) and on medium Earth orbits (MEO) in order to provide personal communication from (almost) every point on the Earth. A problem of LEO and MEO systems is the time-variant position of the satellites which results from the lower altitude of the satellites. In order to establish intersatellite links (ISLs), it is necessary to know the exact positions of the satellites and to calculate the azimuth and elevation angles of two satellites that are using ISLs. The circular polar satellite constellation is examined for the use of ISLs. It is shown how changes of a special orbit parameter influences the use of ISLs and the probability of visibility. Equations for the azimuth and the elevation angles of two satellites are derived and examinations are presented for an example system, a system that is using ISLs and is based on the circular polar satellite constellation.