Satellite Constellation Design for Zonal Coverage Using Genetic Algorithms
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Satellite Constellation Design for Zonal Coverage Using Genetic Algorithms 1 T. A. Ely,2 W. A. Crossley,' and E. A. Williams 4
Abstract The problem of constellation design presents many difficulties in the form of multiple, competing objectives and a complex design space. Past approaches to solving this problem have been to limit the number of objectives and/or simplify the geometry (such as restricting the design procedure to using only circular orbits) so that a tractable solution is obtainable. The genetic algorithm (GA) has been used in many design problems, but has seen limited application to the problem of constellation design. The GA has the ability to handle objectives of mixed (continuous and discrete) type and complex design spaces that do not have convenient analytical representations. With these capabilities, it becomes possible to consider the use of eccentric, inclined orbits for designing constellations efficiently. A method to evaluate coverage associated with ellipitical orbits via a streets-of-coverage approach was derived for this effort. This paper describes a method for applying a GA in a gaming approach for multiobjective design of satellite constellations for zonal coverage.
The algorithm is applied to a northern hemisphere coverage problem, a CONUS-like coverage problem, and an ELLIPSO™-Iike coverage problem. Results are presented that suggest elliptic orbits may be beneficial to reduce the number of satellites needed for certain coverage problems.
Introduction Traditional satellite constellation design strategies often address the problem of global coverage, however for many applications this is not necessary; coverage over a zonal region between specified latitudes is sufficient. This is typically the case with satellite communication systems that require coverage over the Earth's most IA prior version of this paper (AAS 98-128) was presented at the AAS/AIAA Spaceflight Mechanics Meeting, Monterey, California, February 1998. 2Visiting Assistant Professor, School of Aeronautics and Astronautics, Purdue University; currently Staff Engineer, Jet Propulsion Laboratory, Mail Stop 301-125L, 4800 Oak Grove Drive, Pasadena, CA 91109-8099. 3Assistant Professor, School of Aeronautics and Astronautics, Purdue University, 1282 Grissom Hall, West Lafayette, IN 47907-1282. "Graduate Student, School of Aeronautics and Astronautics, Purdue University, 1282 Grissom Hall, West Lafayette, IN 47907-1282.
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populous regions, such as the northern hemisphere [1]. In order to have an analytically tractable problem, past approaches to solving the zonal coverage problem impose circular orbits as a constraint [2, 3]. It is possible that more efficient constellation designs can be obtained using eccentric orbits. A satellite that is in a circular orbit produces a coverage circle with a constant central angle, thus areas outside of the desired zonal region receive as much coverage from a satellite as regions that lie within the desired zone [2]. On the other hand, the coverage circ
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