Key issues in constellation design optimization for NGSO satellite systems

This paper presents various constellation design criteria for satellite systems in non-geostationary orbits (NGSO). Key design parameters, constraints, and tradeoffs are discussed for two classes of orbits: circular and non-circular. Circular orbits, such as the low earth orbits (LEO), the medium earth orbits (MEO), and the highly inclined geosynchronous orbits (IGSO), have equal coverage period for both north and south hemispheres while non-circular orbits such as the various type of elliptical orbits provide more focused coverage period at certain specific geographic locations. Different services require various constraints including delay, power economics, coverage region, frequency sharing, total capacity, satellite and launch-vehicle numbers. Detailed discussion of the relationship between these constraints and constellations are provided. A comparison between a proposed benchmark MEO system with other proposed broadband NGSO satellite systems is presented to demonstrate the importance of constellation design to enhance frequency-sharing capability. A potential “satellite highway” accommodating families of elliptical geosynchronous satellites is also presented. This is a novel approach to regulatory NGSO constellations which will facilitate sharing valuable resources of spectrum and useful spatial areas.