Abstract :
A number of new mobile satellite communications systems are currently being developed that do not make use of satellite constellations based on the geostationary or Clarke orbit traditionally used for communication satellites. Although there are systems being planned that make use of non-circular orbits, the main proponents are based on circular orbits of various altitudes and constellation density. The design of these systems is subject to many constraints, not least because of the enormous cost and risk associated with the design and implementation of such systems; frequently on a global scale. Amongst these constraints are those imposed by propagation factors associated with the Earth-space link and the mobile environment. This paper describes some of these factors and how they may influence the design of some planned mobile satellite communications systems
