What is an EPIRB?
An Emergency Position Indicating Radio Beacon (EPIRB) is a critical maritime safety device required under SOLAS regulations for all vessels over 300 gross tonnes on international voyages. When activated — either manually by crew or automatically on water immersion (float-free EPIRBs deploy and activate automatically if a vessel sinks) — the EPIRB broadcasts a 406 MHz distress signal containing a unique vessel identifier code and, in GPS-equipped models, precise GPS coordinates.
The COSPAS-SARSAT system
EPIRB signals are detected by the COSPAS-SARSAT international satellite search and rescue system — a partnership between the USA (NOAA), Russia (Roscosmos), Canada (CSA), and France (CNES). The system uses a combination of LEO satellites (LEOSAR) for near-real-time detection and GEO satellites (GEOSAR) for immediate alert reception. Modern medium-altitude earth orbiting satellites (MEOSAR) using GPS, GLONASS, and Galileo satellites equipped with search-and-rescue payloads now provide near-instantaneous global coverage with position accuracy to <100 m.
Registration and false alarms
Every EPIRB must be registered with the national authority to link the beacon's unique 15-digit MMSI code to vessel details (name, owner, contacts). This registration enables rescue coordinators to verify whether an alert is genuine before dispatching resources. False activations — the leading cause of COSPAS-SARSAT system workload — are estimated to account for over 95% of all alerts received, often caused by improper stowage, battery replacement without re-registration, or accidental water exposure during testing.