Cospas-Sarsat is an international, humanitarian search and rescue system that uses satellites to detect and locate emergency beacons carried by ships, aircraft, or individuals. The system consists of a network of satellites, ground stations, mission control centers, and rescue coordination centers.
When an emergency beacon is activated, the signal is received by a satellite and relayed to the nearest available ground station. The ground station, called a Local User Terminal, processes the signal and calculates the position from which it originated. This position is transmitted to a mission control center where it is joined with identification data and other information on that beacon. The mission control center then transmits an alert message to the appropriate rescue coordination center based on the geographic location of the beacon. If the location of the beacon is in another country's area of responsibility, then the alert is transmitted to that country's mission control center.
The Cospas-Sarsat system provides a tremendous resource for protecting the lives of aviators and mariners that was unthinkable prior to the Space-Age. With a 406 MHz beacon, a distress message can be sent to the appropriate authorities from anywhere on Earth 24 hours a day, 365 days a year.