INMARSAT-C
INMARSAT-C is a satellite-based GMDSS communication system that provides two-way text messaging, distress alerting, safety communications, and Maritime Safety Information (MSI). As required under SOLAS Chapter IV and IMO regulations, INMARSAT-C supports reliable long-range communication for ships operating beyond coastal radio coverage.
Is INMARSAT-C mandatory under SOLAS?
Yes. INMARSAT-C is mandatory for ships operating in Sea Area A3, as per SOLAS Chapter IV (GMDSS).
What is the main purpose of INMARSAT-C?
Its primary purpose is distress alerting, safety communication, and receipt of MSI, including NAVTEX-type information.
Does INMARSAT-C support distress alerts?
Yes. It provides priority distress alerting with position data sent directly to Rescue Coordination Centres (RCCs).
What type of communication does INMARSAT-C provide?
INMARSAT-C supports store-and-forward text messaging, not voice communication.
How is Maritime Safety Information received via INMARSAT-C?
MSI is received through Enhanced Group Call (EGC) services such as SafetyNET.
Is a printer required for INMARSAT-C?
Yes. SOLAS requires a printer or equivalent display to ensure MSI messages are permanently recorded.
How is INMARSAT-C tested?
Testing is carried out via routine test messages and during GMDSS inspections, without sending real distress alerts.
Does INMARSAT-C require GPS input?
Yes. Continuous position input from GPS is required for accurate distress alerting.
How often should INMARSAT-C be tested?
Routine testing should be carried out:
Weekly or monthly, as per SMS
Before sailing
During GMDSS surveys and PSC inspections
Can INMARSAT-C operate in polar regions?
No. INMARSAT-C coverage does not include Sea Area A4 (polar regions). Alternative systems such as Iridium GMDSS are required
Conclusion
INMARSAT-C forms the backbone of GMDSS communications, meeting SOLAS and IMO requirements for global distress alerting and safety messaging. Proper maintenance, testing, and crew familiarity ensure uninterrupted safety at sea.