The International Cospas-Sarsat Programme is a 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. It is best known as the system that detects and locates emergency beacons activated by aircraft, ships and backcountry hikers in distress.
LUT Local User Terminal, a satellite data processing centre, part of the Cospas-Sarsat international satellite system for search and rescue (SAR)
Satellites Constellations
LEOSAR
LEOSAR predates the GEOSAR system, and it complements it. LEOSAR satellites are monitored by 44 LEOLUTs (low Earth orbit local user terminals).[10] The complementary LEOSAR satellites provide periodic coverage of the entire earth with an emphasis on polar regions. The LEOSAR satellites operate in a store-and-forward mode for 406 MHz signals --- they store distress signals and forward them to the next LEOLUT ground station they overfly. The five-satellite polar-orbit constellation of the LEOSAR system provides frequent coverage of the poles with approximately 100 minute orbits. Wikipedia
GEOSAR
The GEOSAR satellites are monitored by 16 GEOLUTs (Geostationary Earth Orbit Local User Terminals.)[12] The GEOSAR satellites provide continuous coverage of the entire earth below about 70 degrees latitude with a view toward the equatorial sky. Some locations have poor radio reception toward the GEOSAR satellites and polar regions are not well covered. Wikipedia