Inmarsat

Inmarsat provides global mobile satellite telephone and data services using a fleet of geostationary communications satellites operating primarily in the L-, Ka-, and S-bands. Founded in 1979 to provide satellite communications for maritime users, Inmarsat has since expanded its services to include aeronautical and land-mobile markets.

Originally established as the International Maritime Satellite Organization (INMARSAT), the entity was a non-profit intergovernmental organization. In April 1999, its regulatory and oversight functions were transferred to the International Mobile Satellite Organization (IMSO), while the operational business was privatised as Inmarsat Ltd, headquartered in the United Kingdom.

Inmarsat’s initial services relied on capacity leased from the US Navy’s MARISAT satellites and ESA’s MARECS spacecraft. In the early 1990s, Inmarsat deployed its first proprietary constellation, Inmarsat-2, which supported the Inmarsat-A analog maritime service.

Between 1996 and 1998, the Inmarsat-3 constellation was launched, comprising five geostationary L-band satellites delivering Inmarsat-B and Inmarsat-C services. Each Inmarsat-3 satellite provided approximately 150 channels using two transponders. The satellites had a dry mass of about 895 kg and generated approximately 2.8 kW of electrical.

Inmarsat introduced the Broadband Global Area Network (BGAN) service in the mid-2000s, initially supported by Inmarsat-3 satellites and later expanded with the launch of the Inmarsat-4 series, including Alphasat in 2013.

In 2015, Inmarsat deployed its Global Xpress high-throughput satellite (HTS) system using three Inmarsat-5 Ka-band satellites, providing near-global broadband coverage for maritime and aeronautical users. In 2017, Inmarsat launched an S-band satellite to support the European Aviation Network (EAN), combining satellite and terrestrial LTE infrastructure.

On 22 December 2021, Inmarsat launched the first of its next-generation Inmarsat-6 (I-6) satellites. Each I-6 spacecraft carries both L-band (ELERA) and Ka-band (Global Xpress) payloads, with significantly increased per-beam power and flexible digital payload capability compared with earlier generations.

Global voice services

• IsatPhone 2: Voice telephony, SMS, GNSS positioning, and data up to ~20 kbps.
• IsatPhone Link: Fixed and semi-fixed voice connectivity with low-rate data.
• FleetPhone: Cost-effective maritime voice services.

Broadband Global Area Network (BGAN)

• BGAN: IP packet-switched service up to 800 kbps and a streaming-IP service from 32 kbps up to X-Stream data rate. Circuit-switched Mobile ISDN services at 64 kbps.
• FleetBroadband (FB): Maritime broadband services.
• SwiftBroadband (SB): Aeronautical broadband services.

High throughput services

• Global Xpress: Ka-band IP broadband services with typical downlink rates up to ~50 Mbps and uplink rates up to ~5 Mbps, with end-to-end latency of approximately 600-700 ms.
• European Aviation Network (EAN): Hybrid satellite-terrestrial system providing multi-Gbps aggregate capacity across European airspace.

M2M communications

• BGAN M2M: A global, IP-based low-data rate service, for users needing high levels of data availability and performance in permanently unmanned environments, such as pipelines and oil well heads, or backhauling electricity consumption data within a utility.
• IsatM2M: A global, short burst data, store and forward service that will send messages of 10.5 bytes or 25.5 bytes and receive 100 bytes.

Inmarsat’s ELERA network provides L-band services to government and defense users, with data rates up to approximately 1.7 Mbps. ELERA is being further enhanced by the I-6 satellites and forms part of Inmarsat’s ORCHESTRA concept, which aims to integrate GEO, LEO, and HEO satellite assets with terrestrial 5G networks to provide adaptive global connectivity.

In November 2021, Viasat announced its acquisition of Inmarsat in a transaction valued at approximately US$7.3 billion. The merger was completed on 30 May 2023. Following the merger, the combined fleet comprised approximately 19 operational satellites across the L-, Ka-, and S-bands, with plans to expand the constellation, including HEO satellites to extend coverage into polar regions.

Three Inmarsat-8 (I-8) satellites are planned for launch later in the decade, featuring significantly smaller form factors and advanced payload capabilities. In 2022, Inmarsat and Honeywell announced SwiftJet, a next-generation L-band aeronautical service supporting data rates of up to approximately 2.6 Mbps for cockpit and safety-critical applications.

In late May 2023, Australia and New Zealand signed a $190 million, 20-year agreement with Inmarsat to improve the accuracy of GPS signals to as little as 10 cm. SouthPAN, a Satellite-Based Augmentation System (SBAS) which has been live since 2022, will formally broadcast from one of Inmarsat’s I-8 satellites from 2027. An additional satellite is also being procured to provide SouthPAN services. SouthPAN is that provides huge improvements to positioning and navigation systems, using a combination of reference stations, telecommunications infrastructure, computing centers, signal generators, and satellites. A number of distributed ground stations monitor signals from GNSS satellites and send measurement information to correction processing facilities, which compare each station’s known location with position data from the satellites, and then broadcast the data to all users, who combine SouthPAN’s data with their own observations of GNSS satellites.