How Inmarsat Works
Inmarsat owns and operates three constellations of communication satellites and a total of 12 spacecraft. Together they form the backbone of the world's most versatile, reliable, commercial satellite communications network.
Flying in geosynchronous orbit 35,786km (22,236 miles) above the Earth, the satellites are positioned in nine orbital locations to give seamless global coverage (excluding polar regions above 82 degrees latitude).
Inmarsat launched the world's first global mobile satellite communications system to enable merchant ships to stay in touch or call for help in an emergency.
The Satellite Fleet
Inmarsat-5 & Global Xpress
The world's first global Ka-band mobile satellite system, delivering high-speed broadband to compact user terminals at up to 50Mbps. Built by Boeing on the powerful 702HP platform.
- I-5 F1: Commercial service July 2014
- Covers Europe, Middle East, Africa, Asia
- Global coverage with three satellites
Alphasat & I-4 Series
Alphasat is one of the most technically advanced communications satellites ever flown. The size of a London double-decker bus with a mass of over 6.6 tonnes at launch.
- Largest European telecom satellite ever built
- I-4 won Royal Academy MacRobert Award
- World's first global 3G network
Inmarsat-3 Series
The workhorses of the L-band fleet. First generation to use spot-beam technology, launched between 1996-1998. Developed by Lockheed Martin.
- All five satellites currently in service
- 2,800W end-of-life power rating
- GPS/Glonass navigation enhancement
Geostationary Orbit Advantages
Inmarsat satellites operate in geostationary orbit, which means they remain fixed relative to a point on Earth. This provides several key benefits:
Stable Connections
No handoffs between satellites means consistent, reliable connections
Fixed Antenna Pointing
Ground equipment can use fixed antennas, simplifying installations
Wide Coverage
Each satellite covers approximately one-third of the Earth's surface
Fewer Satellites Needed
Global coverage achieved with just 3-4 satellites
Coverage Note
*Inmarsat provides near-global coverage but does not cover the extreme polar regions (above approximately 82 degrees latitude). For true polar coverage, consider Iridium.
Legacy & Innovation
Inmarsat was founded in 1979 by 86 countries with a maritime safety mandate. Today, the London-headquartered company continues to innovate and contribute to global connectivity through its network of satellites.
Decommissioned: Inmarsat-2
The first wholly owned Inmarsat satellites were built by British Aerospace and launched in 1990-92. Despite a planned design lifespan of 10 years, the final I-2 satellite continued in active service until December 2014, demonstrating the exceptional build quality and reliability that Inmarsat is known for.