Operational use of Cospas-Sarsat by SAR agencies started with the crash of a light aircraft in Canada, in which three people were rescued (September 10, 1982). Since then, the System has been used for thousands of SAR events and has been instrumental in the rescue of over 33,000 lives worldwide.
The basic Cospas-Sarsat concept is illustrated in the adjacent figure. The System is composed of:
distress radiobeacons (ELTs for aviation use, EPIRBs for maritime use, and PLBs for personal use) which transmit signals during distress situations;
ground receiving stations, referred to as Local Users Terminals (LUTs), which receive and process the satellite downlink signal to generate distress alerts; and
- Mission Control Centers (MCCs) which receive alerts produced by LUTs and forward them to Rescue Coordination Centers (RCCs), Search and Rescue Points Of Contacts (SPOCs) or other MCCs.
The Cospas-Sarsat System includes two types of satellites:
- satellites in low-altitude Earth orbit (LEO) which form the LEOSAR System
- satellites in geostationary Earth orbit (GEO) which form the GEOSAR System
Cospas-Sarsat has demonstrated that the GEOSAR and LEOSAR system capabilities are complementary. For example the GEOSAR system can provide almost immediate alerting in the footprint of the GEOSAR satellite, whereas the LEOSAR system:
provides coverage of the polar regions (which are beyond the coverage of geostationary satellites);
can calculate the location of distress events using Doppler processing techniques; and
is less susceptible to obstructions which may block a beacon signal in a given direction because the satellite is continuously moving with respect to the beacon.
For a more detailed description of the Cospas-Sarsat System see document C/S G.003 "Introduction to the Cospas-Sarsat System".