Satellites also provide mobile telephony services. Satellite mobile telephony enables regional to near-global coverage depending on the satellite or constellation, using handsets that communicate directly with a satellite. Mobile satellite telephone service is provided by satellite constellations in LEO, such as Iridium and Globalstar, and by satellites in GEO, such as Inmarsat, Thuraya, and ACeS. These services are provided by satellites primarily using the L-band. Satellites providing mobile phone and data services often are referred to as mobile satellite service (MSS) satellites.
Satellites have provided trunking for long-distance telephone service for decades. Most long-distance traffic is now routed over cable, avoiding the lag and other reductions in quality (such as echo) associated with satellite telephone calls. Areas or countries lacking terrestrial backbone still rely on satellite connectivity to the publicly-switched telephone network. Telephone companies or nations lease C-band or Ku-band transponders on GEO satellites. Telephony, along with broadcast television, discussed above, and data services are common FSS applications.
One MSS industry leader, Iridium, is implementing a major network upgrade. In June 2010, Iridium selected France’s Thales Alenia Space as prime contractor for its second-generation satellite constellation, named Iridium NEXT. The upgraded network will consist of ## active and ## spare satellites, scheduled for launch between 2015 and 2017.[
GEO satellites can allow a signal to be beamed over a wide fixed coverage area, with the potential to reach a third of the Earth’s surface. They are thus ideal for FSS operators, who often use them to send a single data stream to many stationary antennas in one or more continents. FSS satellites provide DTH video or internet services, corporate network connectivity, broadcast video distribution, and secure communications for the military. Of the ## total active satellites in 2012, ## are communications satellites.
Another MSS industry leader is Iridium, which operates a LEO constellation of ## active satellites to provide global coverage. The Iridium constellation uses intersatellite links to route network traffic directly between spacecraft, avoiding the need for multiple hops between space and ground to relay signals around the world. Like Inmarsat, Iridium is significantly upgrading its network to reach new customer bases with new technology.
The MSS sector was created to address a specific market that was underserved by FSS: maritime voice and data, enabling emergency communications for ships at sea. Subsequent MSS systems tried to create ubiquitous coverage for land and sea customers, especially in areas that were underserved by terrestrial mobile telephony. For years, MSS systems were designed using satellites in GEO or LEO that were able to transmit low-data rate information to mobile receiving systems, such as satellite telephones or receiving stations on ships.
GEO satellites can broadcast a signal to one-third of the Earth’s surface. They are ideal for FSS operators, who broadcast to antennas spread across several continents. Of the ## communications satellites active at the end of 2013, ## were located in GEO and were primarily used for FSS. The dominant players in satellite communications have been Intelsat, SES, Eutelsat, and Telesat. These four companies have expanded their respective fleets through construction and launch as well as consolidation and acquisition of competitors’ satellites.
The number of FSS satellites has grown tremendously over the past five years in response to increased demand. Deregulation of international markets has sparked the rise of new companies providing content to customers via satellite. Harmonization of digital transmission standards has helped manufacturers, allowing for economies of scale and more cost-effective distribution.
Telecommunications satellites include all spacecraft whose main mission is to collect, relay, or broadcast data, which may include voice, video, and other information. Depending on the type of system, communications satellites range from very small to very large satellites and can operate from all Earth orbits. The vast majority fall into one of two categories: geosynchronous orbiting (GEO) satellites and large constellations located in Low Earth Orbit (LEO)/Medium Earth Orbit (MEO).
Iridium’s LEO constellation of ## active and ## spare satellites relay signals to each other directly, unlike other systems that require multiple hops between space and the ground to send signals around the world. In June 2010, the company named France’s Thales Alenia Space as prime contractor to construct the communications payload for Iridium’s second-generation, ##-satellite constellation Iridium NEXT.