Continuous earth-to-space communications require that at least one satellite be in view of the ground station at all times. The satellite constellations discussed in this Note are designed to maximize the probability that one or more of the satellites in the constellation will always be at an elevation angle of 20 degrees or more above the horizon of the ground station. (This maximum elevation angle is based on the assumption that millimeter waves will be used for communication.) Constellations of satellites in circular orbits at synchronous and five times synchronous altitude and also in elliptical orbits are presented. Some of the constellations are designed to maximize global coverage (i.e., a ground station located anywhere on earth) and others are designed to maximize coverage for the northern hemisphere.
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