Emergency Position-Indicating Radio Beacons
Cospas-Sarsat is an international satellite-based search and rescue (SAR) distress alert detection and information distribution system, established by Canada, France, the United States, and the former Soviet Union in 1979.
The system consists of both a ground segment and a space segment:
The space segment of the Cospas-Sarsat system currently consists of SAR processors aboard 4 geosynchronous satellites called GEOSARs and 5 low-earth polar orbit satellites called LEOSARs.
Cospas-Sarsat began tracking the two original types of distress radiobeacons in 1982. Specifically, these were:
More recently, a new type of distress radiobeacon became available (in 2003 in the USA)
The four founding countries led development of the 406 MHz marine EPIRB for detection by the system. The EPIRB was seen as a key advancement in SAR technology in the perilous maritime environment. The aviation community had already been using the 121.5 MHz frequency for distress, so ELTs for general aviation were created using 121.5 MHz, a frequency listened to by the airlines. Military beacons using the 243.0 MHz frequency could also be detected by the system.
The design of distress radiobeacons as a whole has evolved significantly since 1982; the newest 406 MHz beacons incorporate GPS receivers; such beacons transmit highly accurate positions of distress almost instantly to SAR agencies via the GEOSAR satellites. The advent of such beacons has created the current motto of SAR agencies --- .
SARSAT is an acronym for Search And Rescue Satellite-Aided Tracking.
Cospas-Sarsat is an element of the Global Maritime Distress Safety System (GMDSS). Automatic-activating EPIRBs are now required on International Convention for the Safety of Life at Sea (SOLAS) ships, commercial fishing vessels, and all passenger ships, are designed to transmit to a Rescue Coordination Centre a vessel identification and an accurate location of the vessel from anywhere in the world.
The U.S. & Canadian Coast Guard have outstanding websites with even more information on EPIRBs, including some that work through the INMARSAT System.