low earth orbit search and rescue (LEOSAR)
Leosar satellites are LEO satellites, Low Earth Orbiters, which orbit the Earth's surface relatively quickly in a low orbit of 800 km to 1,000 km. They are used in combination with the Geosar satellites to rescue people in emergency situations.
The orbit times of the Leosar satellites are between 45 and 60 minutes. In the Cospas-Sarsat system, between 5 and 7 LEO satellites orbit the Earth in a polar orbit.
The Leosar satellites use the Doppler effect, which is based on the relative wavelength shift between moving transmitters and receivers, to locateemergency transmitters. In this case, between the relatively fixed position of the distress transmitter and the high speed of the Leosar satellite. As long as the Leosar satellite approaches the distress transmitter, the frequency increases. After the satellite has flown over the emergency transmitter, it drops again. This change in frequency indicates the position of the emergency transmitter. The positioning accuracy depends on the frequency stability of the international emergency radio frequency of 406 MHz of the emergency transmitter.