MOBILE SATELLITE SYSTEMS IN GEO

Mobile satellite service (MSS) systems have mobile users. Mobile users may be on land, on ships, or in airplanes. Some MSS systems have geostationary orbit (GEO) satellites but some have non‐GEO. This chapter describes five GEO MSS systems. These include: Thuraya, two spacecraft, first one launched in 2003, Inmarsat‐4 series, three spacecraft, first one launched in 2005, TerreStar, two spacecraft, SkyTerra, one spacecraft, launched in 2010, and Inmarsat‐5 series, four spacecraft, first launch in 2013, also known as Global Xpress or simply GX. Thuraya uses a combination frequency‐division multiplexing/time‐division multiplexing multiplexing on all links. The TerreStar system used the communications standard GMR‐1 release 3 for both the user and feeder links. The SkyTerra system is similar to TerreStar in many ways. Its key features are as follows: one operating spacecraft, and user‐ground station links. The Inmarsat system with the Inmarsat‐5 spacecraft provides services including broadband Internet access, multimedia, and voice over IP.