Satellite telephony systems operate mainly through two orbital types:
geostationary orbit (GEO), about above Earth, and
low Earth orbit (LEO), about . The orbit determines coverage area, latency, and terminal design.
Geostationary systems satellite, 1963 GEO satellites appear fixed in the sky, allowing near-global coverage with few satellites. The long signal path introduces latency but supports higher data throughput than LEO networks. GEO service is reliable up to roughly 70° latitude; signal quality decreases near the poles or in obstructed terrain. Notable GEO-based operators include: •
ACeS – Indonesia-based operator active 2000–2014 •
Inmarsat – Founded 1979, provides global coverage except polar regions •
Thuraya – UAE-based, operating since 1997 across Europe, Africa, Asia, and Australia •
MSAT /
SkyTerra – North American operator offering mobile and fixed terminals •
Terrestar – U.S. operator using geosynchronous orbit •
Tiantong – Chinese GEO system for regional voice and messaging services
Low Earth orbit systems LEO satellites orbit Earth every 70–100 minutes. Continuous service requires constellations of dozens of satellites, as each satellite remains visible for only several minutes. Major operators: •
Globalstar – 48 active satellites covering most land areas; depends on ground gateways within view of satellites •
Iridium – 66 active near-polar satellites with inter-satellite links providing global coverage Both systems launched in the late 1990s, experienced bankruptcy, and were later restructured. Typical data speeds range from 2.4 to 9.6 kbit/s.
Emerging hybrid networks In 2022,
T-Mobile US and
SpaceX announced a partnership using second-generation
Starlink satellites to provide limited mobile coverage via existing
LTE spectrum.
AST SpaceMobile is developing a
3GPP-compliant space network linking standard smartphones to satellites in areas lacking terrestrial coverage. In 2024,
Iridium announced “Project Stardust”, a planned 5G non-terrestrial service for messaging and
IoT devices. == Numbering ==