User position estimation for search and rescue using satellite in LEO constellation

Based on the Doppler measurements from a user´s beacons, a simple algorithm is developed to estimate the user position for search and rescue purposes. The algorithm uses the measurements only at the beginning, middle and end of visibility of the satellite over the user region. In the case of a constellation of satellites in low Earth orbits (LEO), this algorithm is shown to yield accuracies better than 1 km by utilising the estimates (of the user position) from different satellites through a recursive average filter. Simulation studies are carried out for three different orbit altitudes and different user latitudes. With the increasing interest in LEO constellations for communications, it is hoped that such position estimation algorithms will further enhance the application of LEO constellations