Accuracy bounds for positioning of geostationary data relays using LEO satellites

The use of Low Earth Orbit (LEO) satellites as navigation satellites for geostationary data relays promises positioning with centimetre accuracy. Thereby, the number of visible LEO satellites, the geometry of the LEO constellation, the antenna gains and the signal design have a huge influence on the achievable precision. In addition, LEO satellite position biases propagate into geostationary (GEO) satellite positioning errors. This paper provides a lower bound for the achievable GEO positioning accuracy based on these effects and gives an insight into the correlation between the GEO satellite position and clock estimates.