Medium and high altitude orbits

A communication satellite in Medium and High Altitude Orbits must be visible from the regions concerned during the period when it is desired to provide a links for Fixed (FSS) and Mobile Satellite Service (MSS), what can vary from a few to 24 hours per day. These kinds of orbits are circular and are in function to cover a given geographical region at the same local time each day and to offer continuous service to all Mobile (MES), Fixed (FES) and Land Earth Stations (LES). The duration of uninterrupted communication service, which such satellite can provide in any region on the terrestrial surface, is a function of his altitude and latitude of the satellite FSS or MSS receivers or transceivers. The most popular and used type of the Medium and High Altitude Orbits today is well known Geostationary Earth Orbit (GEO) for both FSS and MSS applications with coverage between 75° N and S latitude. The GEO constellation cannot provide coverage for both Polar Regions. On the other hand, Highly Inclined Medium Earth Orbit (MEO) today is mostly in use for Global Navigation Satellite Systems (GNSS), such as first generation of GNSS-1, both military systems, the US GPS and Russian GLONASS. This orbit is also suitable for the European second generation GNSS-2 civilian Galileo system. The Geosynchronous Inclined Orbit (GIO) can be also successfully implemented for GNSS and satellite communication purposes, but is not suitable for covering Polar Regions.