About GSPS

Inmarsat’s Global Satellite Phone Service (GSPS) is an established and proven global voice and text satellite communication service. GSPS operates over the Inmarsat-4 and Alphasat satellites using an enhanced GMR-2 air interface (GMR-2+). The service is a satellite enabled service designed to provide voice, SMS and data connectivity via satellite communications equipment in land and maritime environments. There are a number of different GSPS Satellite Terminals which provide a range of satellite communication capabilities addressing the needs of users. GSPS operates over L-band.

GSPS supports the following services:

  • Voice service using a 2.4kbps codec
  • SMS messaging
  • Data service using a 2.4kbps circuit switch connectivity
  • Supplementary services

Please click here for a GSPS coverage map.

Combined I-4 Satellites and Alphasat Coverage

GSPS services are offered globally down to a minimum of 5 degrees elevation to the satellite. Towards the edge of coverage, greater user cooperation is required. Users are advised to follow the user interface instructions in those particular areas.

On the Alphasat footprint GSPS coverage has been prioritised in the region north of 44 degrees south. GSPS users may experience a degradation of performance south of this latitude.


Each satellite is served by a single combined, co-located Network Control Centre-Gateway (NCC-GW). Two functionally identical NCC-GW sites are required and strategically located in Europe (Fucino, Italy) and North America (Paumalu, Hawaii).

Inmarsat is responsible for establishing terrestrial interconnect arrangements for call termination from the gateway sites in Fucino and Paumalu.


GSPS requires GMR2+ compliant products with tested core technology to work with the network. Today Inmarsat provides VAMs GSPS core modules to support development.

Various devices using these core modules are available to access GSPS services:

  • IsatPhone for land and maritime services
  • FleetPhone for maritime services
  • IsatPhone Link for land services

Not all Satellite Terminals support all voice, data, SMS and supplementary services.