How do Cospas Sarsat beacons work?

The COSPAS/SARSAT system utilises two satellite arrays to provide distress alert and location data to search and rescue authorities.  The GEOSAR system can provide near immediate alerting within the coverage of the receiving satellite.  The LEOSAR system provides coverage of the polar region beyond the range of the GEOSAR system. LEOSAR satellites can calculate the location of distress events using Doppler processing techniques and are less susceptible to obstructions which could block a signal in a given direction.  The system is comprised of instruments on board the satellites which detect the signals from the distress beacons.

Ground receiving stations, referred to as Local Users Terminals (LUTs) receive and process the satellite downlink signal to generate the distress alerts. The distress alerts, generated by the LUTs, are then received by Mission Control Centres (MCCs) which then forward the alert to Rescue Co-ordination Centres (RCCs), Search and Rescue Points of Contacts (SPOCs) and other MCCs.

A new generation os SAR transponders are being carried on newly launched global navigation satellites (GNSS).  Currently these are being launched on the European Galileo satellites, but they will also be carreid on GPS and GLONASS satellites.  These satellites all operate in a higher orbit than the LEOSAR satellites and will be known as MEOSAR.  The increased number of satellites will dramatically improve the detection times of distress alerts.  The MEOSAR transponders are fully compatibly with current generation EPIRBs and PLBs, but future beacons will use “2nd generation” technology improving location accuracy over the existing system.

This Cospas Sarsat Video explains the advantages of having an EPIRB or PLB for use in emergency and what happens when the beacon is activated.