Inmarsat-C is a two-way, packet data service operated by the telecommunications company Inmarsat. The service is approved for use under the Global Maritime Distress and Safety System (GMDSS), meets the requirements for Ship Security Alert Systems (SSAS) defined by the International Maritime Organization (IMO) and is the most widely used service in fishing Vessel Monitoring Systems (VMS).
The service offers data transfer; e-mail; SMS, crew calling; telex; remote monitoring; tracking (position reporting); chart and weather updates; maritime safety information (MSI); maritime security; GMDSS; and SafetyNET and FleetNET services.
The service is operated via an Inmarsat-C Transceiver or a lower-power mini-C Transceiver. Both offering and approved for the same service.
The service is available for maritime, land mobile and aeronautical use.
This system has also been used to track the BBC's project "The Box". BBC News is following a container around the world for a year to tell stories of globalization and the world economy.