Satellite phone

A satellite phone (also called a satellite telephone or satphone) is a type of mobile phone that connects to the public switched telephone network through orbiting satellites instead of terrestrial cell sites. They function in areas without terrestrial network coverage but require line-of-sight to a satellite. Most support voice, text, and low-bandwidth data services.

Satellite phones are used in areas where conventional communication infrastructure is unavailable or has been disrupted. Typical applications include maritime and aviation communication, remote expeditions, mining, logistics, and emergency response.

Early handsets were large and required deployable antennas, while later models are comparable in size to ordinary smartphones. Fixed ship and vehicle installations use directional microwave antennas that track satellites automatically. Smaller systems may rely on VoIP over satellite internet links such as BGAN or VSAT. Indoor reception is limited and may require external antennas or repeaters. Unmodified smartphones that do not support sending or receiving data from satellites.

The first voice signals relayed via satellite were transmitted in 1958 using the experimental SCORE satellite, soon after the launch of Sputnik 1. MARISAT (1976) became the first dedicated mobile communications satellite and was later integrated into the Inmarsat organization, founded in 1979.

Satellite telephony systems operate mainly through two orbital types: geostationary orbit (GEO), about 35,786 kilometres (22,236 mi) above Earth, and low Earth orbit (LEO), about 640 to 1,120 kilometres (400 to 700 mi). The orbit determines coverage area, latency, and terminal design.

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:

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.