Small Satellite Constellations for EHF Polar Coverage

Because atmospheric attenuation is greater for EHF frequencies than lower frequencies, it is necessary to design EHF satellite constellations so that the minimum elevation angles of the ground station antennas are larger than for satellite communication links using lower frequencies. The need for larger elevation angles reduces the coverage provided by geosynchronous equatorial satellites. This paper examines how the size of the polar regions not receiving adequate EHF coverage varies with the number of equally spaced equatorial satellites. The suitabilities of 24 hour Tundra, 12 hour Molniya, and six hour circular orbits for providing the missing coverage are then examined. The geographical location requirements for ground stations which link these satellites into global communication networks are analyzed. Three standard small satellite launch vehicles (SSLVs) can launch either three 12 hour Molniya satellites or six circular orbit satellites. While three Molniya satellites complete coverage of the northern hemisphere, six circular orbit satellites complete coverage of the entire globe. Finally, ground station location is shown to be critical for networking Molniya constellations, while circular orbit constellations offer the use of existing defense communication system architecture EHF terminals.