Introduction to inmarsat geo space and ground segments

This article presents retrospective of development Inmarsat space and ground segments as a Geostationary Earth Orbit (GEO) satellite system with significant contribution to the modem maritime and other mobile satellite applications. The technical parameters and comparison of previous and new generations of Inmarsat GEO satellite constellations with their advantages and disadvantages are described. The choice and upgrading of a particular satellite configuration depends mainly on its mission objectives, development trends of satellite mobile service and applications, modernization of onboard equipment and characteristics of the satellite payloads. Each Inmarsat satellite provides global beam spacecraft antenna for global coverage covering approximately one-third of the Earth's surface (including land and sea) and spot beam coverages from an GEO nearly 36,000 kilometers above the Equator. In this orbit each satellite moves at exactly the same rate as the Earth rotates, so remaining in the same position relative to the Earth's surface. Fife generations of Inmarsat GEO satellite constellations, Inmarsat link budget, ground segment, ground networks, coordination and different control centres are introduced.