GMDSS EPIRB, Radar SART and AIS-SART: Key Differences
GMDSS GUIDE · SEARCH-AND-RESCUE LOCATING DEVICES
EPIRB, Radar SART and AIS-SART: three different jobs
A practical comparison of satellite distress alerting and two locating-device technologies for deck officers and cadets.
Reviewed 2 October 2026.
Quick distinction: an EPIRB is a satellite distress beacon; a Radar SART responds to search radar; an AIS-SART transmits AIS messages for locating. Their roles and receiving equipment differ, so they are not interchangeable.
| Device | Primary purpose | What helps rescuers locate it | IMO performance standard |
|---|---|---|---|
| 406 MHz EPIRB | Satellite distress alerting through the applicable Cospas-Sarsat system. | Beacon identity and alert information; homing or positioning features depend on the approved beacon and receiving arrangements. | MSC.471(101) |
| Radar SART | Responds to search radar in the 9 GHz X-band. | A characteristic response on a compatible radar display as the search radar interrogates it. | MSC.510(105) |
| AIS-SART | Transmits AIS locating messages. | A compatible AIS display or system able to receive and present the messages. | MSC.246(83) |
IMO resolutions set performance standards for each device. SOLAS and flag rules determine which equipment a specific vessel must carry.
How to study the differences
- Ask what needs to happen first: notify the search-and-rescue system, or help nearby search units locate a survival craft or person.
- Identify the receiver: satellite distress-alerting system, X-band search radar, or AIS-capable equipment.
- Look at the actual unit’s approved instructions for activation, self-test, mounting, stowage and maintenance; procedures differ by model and installation.
- For a scenario, state the fitted device, vessel status, available receiver and the distress plan. Do not assume that a display on one system proves reception on another.
Memory aid
EPIRB → alert · Radar SART → X-band radar response · AIS-SART → AIS locating messages. This summarizes function only; it is not a substitute for the device manual or emergency plan.
EPIRB → alert · Radar SART → X-band radar response · AIS-SART → AIS locating messages. This summarizes function only; it is not a substitute for the device manual or emergency plan.
During an emergency, follow the vessel’s emergency plan and the master’s instructions.