Geostationary satellite system providing low-data-rate store-and-forward messaging and EGC SafetyNET broadcasts, recognised under GMDSS for Sea Area A3.
Quick facts
Regulation
SOLAS Chapter IV
In practice
Under SOLAS Chapter IV, vessels operating in Sea Area A3 — broadly the ocean areas between approximately 70°N and 70°S served by Inmarsat geostationary satellites — may carry an Inmarsat-C SES (Ship Earth Station) as part of their GMDSS equipment fit. The SES must be capable of transmitting and receiving distress and safety communications and of receiving EGC broadcasts. Regulation 10 of SOLAS Chapter IV specifies the equipment requirements, and IMO Resolution A.807(19) sets the Performance Standards for Inmarsat-C SES equipment.
Regulatory detail & full definition
Inmarsat-C is a low-data-rate, store-and-forward satellite communication service operating through Inmarsat's geostationary satellite network. Unlike voice-oriented services, Inmarsat-C handles text and data messages of up to approximately 32 kilobytes, making it suitable for navigational telex (TELEX), e-mail, and the receipt of Maritime Safety Information via the Enhanced Group Call (EGC) SafetyNET broadcast service.
Under SOLAS Chapter IV, vessels operating in Sea Area A3 — broadly the ocean areas between approximately 70°N and 70°S served by Inmarsat geostationary satellites — may carry an Inmarsat-C SES (Ship Earth Station) as part of their GMDSS equipment fit. The SES must be capable of transmitting and receiving distress and safety communications and of receiving EGC broadcasts. Regulation 10 of SOLAS Chapter IV specifies the equipment requirements, and IMO Resolution A.807(19) sets the Performance Standards for Inmarsat-C SES equipment.
Inmarsat-C terminals incorporate an omni-directional antenna requiring no stabilisation, making them relatively compact and inexpensive compared to higher-bandwidth services. The system supports automatic distress alerting, position reporting, and polling by shore authorities. Coverage does not extend to polar regions above approximately 76°N or below 76°S, for which the Iridium GMDSS service provides an alternative.