Coverage Optimization of Elliptical Satellite Constellations with an Extended Satellite Triplet Method

The design of a satellite constellation is often driven by coverage objectives. Many methods have been developed to evaluate the coverage efficiency of a constellation pattern, but they are often restricted to continuous global coverage analyses of satellites on circular orbits. Unfortunately, a global coverage of the planet is not always the most cost effective paradigm. In many cases, it is better to optimize a constellation according to zonal coverage objectives rather than a global one. Moreover, to further improve the zonal coverage of the satellites, we should switch to elliptical orbits to allow the satellites to stay for a longer time in view of the zonal targets around their apogee. In this paper, we will show that with some modifications we can still use Walker’s coverage analysis algorithm based on satellite triplets to assess the coverage efficiency of satellite constellation patterns on elliptical orbits. As an illustration of the method, we will present the most suited symmetrical patterns to cover the Northern hemisphere. These patterns are an extension of the classical Walker constellations. To limit the search domain, but also because of their remarkable stability, we will use only elliptical orbits with a frozen perigee.