Inmarsat system operates within frequency ranges allocated by the International Telecommunications Union for mobile satellite service.

For communication with subscriber terminals L-frequency is used, including:

direction «Earth — satellite»    1626.5-1660.5 MHz

direction «satellite – Earth» 1525.0-1559.0 MHz

Feeder lines operate within C-range:

direction «Earth — satellite»     6425-6450 MHz

direction «satellite – Earth»    3600-3623  (3600-3630) MHz

Structurally Inmarsat consists of three main parts:

  • space segment consisting of working and reserve geostationary SV;
  • earth segment which includes technical facilities for receipt, processing and transmission of information – land earth stations, as well as means of control of system performance;
  • subscriber satellite stations and terminals: mobile (maritime/river, railroad, automobile, air and other types of transport), portable and stationary satellite terminals. 

At the moment the satellite constellation consists of 14 geostationary satellites and belongs to Inmarsat.


Earth segment includes:

1. Control and management facilities for satellite constellation:

  • Satellite Control Centres (SCC), main and reserve;

Fig. Satellite Control Center  (SCC)


TT&C Stations located in different geographic regions, including TT&S Station «Kashtan» (Moscow region) – in the Russian Federation. 

Fig. TT&C Station


2. System control and management facilities:

Network Operation Center – NOC), main and reserve. NOC is responsible for general performance of Inmarsat system.

Network Operation Center (NOC)


  •   Network Coordination Stations — (NCS). NCS control and maintain Earth station networks;
  •  Satellite Access Stations — (SAS) and GSPS Services Gateway. SAS maintain functioning of BBA services and personal voice communication. 


Satellite Access Station  (SAS)


3. Land Earth Stations

Land Earth Stations (LES) — belong to national operators of Inmarsat network and provide switching of subscribers terminals with land line networks  (PSTN, Internet, Х-25, Telex). LES maintain services provided through Inmarsat satellites 3 generation. At the moment there are about 20 LES functioning in different geographical regions; two of them — LES «Nudol»  (Moscow region) and LES «Nakhodka» (Primorsky region) — are located in the Russian Federation.   

Operator of LES «Nudol» and LES «Nakhodka» is Morsviazsputnik.

Inmarsat system is the aggregate of standards and systems (subsystems) using the same satellites and, as a rule, common Land Earth Stations, however satellite terminals differ significantly by their functions, structure and technical parameters. 

At the moment Inmarsat system has terminals that submit to the subscribers services which do not require high-speed information exchange (remote location monitoring, M2M solutions, short messages exchange, etc.), as well as modern services providing high-quality telephone connection, transmission of video on-line, work in IP-networks at speed up to 0.5 mbit/s.

History of Inmarsat

Inmarsat  (initial name – International Maritime Satellite Organization Inmarsat)) was established on July 16, 1979 at the initiative of the International Maritime Organization (IMO) and initially had a status of an interstate organization.

The main purpose of establishment of Inmarsat was to provide marine vessels with reliable communications, primarily for enhancement of shipping safety, which included transmission of SOS signals, operative interaction with other vessels and shore services, communication between crew members and passengers with the shore. One of the objectives of Inmarsat is to ensure functioning of maritime satellite communication system in accordance with the requirements of GMDSS – Global Maritime Distress and Safety System.

Initially Inmarsat included 35 states having signed the Operating Agreement, including the USSR, USA, Great Britain, Norway, Japan, Italy, France, FRG and others. All-union organization «Morsviazsputnik» of the Ministry of Marine of the USSR represented the USSR.

In 1982 Inmarsat announced provision of mobile satellite communication services with the use of a resource leased at satellites Marisat  (Comsat), Marecs  (ESA) and Intelsat-5MSC  (Intelsat), and by 1989 the system had more than 8000 Inmarsat marine terminals.

In 1989 the service Land Mobile Service was launches (for land users) and a bit later in 1990 – Aeronautical Service  (for aircrafts).

From 1990 to 1998 Inmarsat put into orbit 9 geostationary communication satellites, including 4 second generation satellites Inmarsat-2 and 5 third generation satellites Inmarsat-3, thus having created a full-scale backup satellite constellation providing global coverage of earth surface.


SV Inmarsat-2                                                                                SV Inmarsat-3


Inmarsat-4 F3 is a communications satellite operated by the British satellite operator Inmarsat. It was launched into a geosynchronous orbit at 22:43 GMT on 18 August 2008 by a Proton-M/Briz-M Enhanced carrier rocket. It is currently located at 97.65° West longitude, providing coverage of the Americas.It entered service on 7 January 2009.

Like the earlier Inmarsat-4 F1 and F2 satellites, Inmarsat-4 F3 was constructed by EADS Astrium, using a Eurostar E3000 bus. It has a mass of 5,960 kilograms, and is expected to operate for 13 years. It was originally slated for launch using an Atlas V 531, but was transferred to Proton due to a large backlog of Atlas launches.

In the United States, Inmarsat ground stations are licensed to operate at 1525-1559 MHz and 1626.5-1660.5 MHz. The 1544-1545 MHz and 1645.5-1646.5 MHz bands are reserved for safety and distress communications



The high-speed Inmarsat-5 (I-5) satellites form the backbone of Inmarsat’s pioneering Global Xpress network.

Built by US manufacturer Boeing’s space division in El Segundo, California, the constellation will operate on Ka-band radio frequencies to deliver a seamless global satellite communications service.

The I-5 satellites, based on Boeing’s proven 702HP spacecraft platform, will deliver consistent high-performance download speeds of up to 50Mbps and up to 5Mbps over the uplink from their position in geosynchronous orbit. Their impressive statistics include:

  • The I-5 body – at 6.98 metres (22.9ft), the height of a double decker bus
  • User beams – 89 Ka-band beams generated by two transmit and two receive apertures
  • Spot beams – six steerable spot beams to direct additional capacity where it is needed
  • Solar arrays – a wingspan of 33.8 metres (111ft)
  • Solar panels – five panels of ultra triple-junction gallium arsenide solar cells generate 15 kW of power at start of service and 13.8 kW by end of life
  • Station-keeping thrusters – a xenon ion propulsion system (XIPS) handles in-orbit manoeuvring
  • Launch mass – 6,100kg
  • Mission lifespan – 15 years

Inmarsat-5 (GX)

By the beginning of 1998 the International Maritime Satellite Organization Inmarsat counted 86 countries-participants having signed the Operating Agreement. 

In April 1998 the 12th extraordinary session of INMARSAT Assembly approved amendments to Convention on International Organization of Maritime Satellite Communication and Operating Agreement stipulating incorporation of a joint-stock limited liability company on the basis of existing organization; this company was to be registered under national law of one of the participants. All assets of Inmarsat were supposed to be transferred to this company, including the title to space segment, and its shares were distributed amount the participants of the Operating Agreement in accordance with their shares in the capital. Herewith it was supposed to maintain inter-government control over fulfillment of obligations on public communication services and, in particular, in respect of Global Maritime Distress and Safety System (GMDSS).

As a result on April 15, 1999 International Maritime Satellite Communication Inmarsat was reorganized into Inmarsat Ltd.

At the same time the Agreement on Headquarters between the Government of Great Britain and International Mobile Satellite Organization (IMSO was signed). Operating Agreement ceased to be effective. Satellites of INMARSAT system and other funds of former international organization INMARSAT have been passed to the restructured company Inmarsat Ltd. It proceeds to manage the global satellite communication system and provide maritime communication services in case of an accident within GMDSS. Amendments to IMSO convention became effective on July 31, 2001.

From July 17, 2000 the company became known as Inmarsat Ventures Ltd., at the moment Inmarsat plc is a joint-stock company (its shares are listed at London stock exchange; its head office is located in London and there are several regional offices. 

Inmarsat office, London.

Inmarsat works in close cooperation with famous international organizations – International Telecommunication Unit, International Maritime Organization (IMO), International Civil Aviation Organization (ICAO), International Mobile Satellite Organization (IMSO), International Hydrographic Organization (IHO), World Meteorological Organization (WMO), etc.

Nowadays Inmarsat is the largest provider of mobile satellite communication services providing to its subscribers telephone and facsimile communication, data transmission at sea, on land and in the air.



Official Inmarsat web-site –