Statistical re-acquisition method for GPS receivers on satellites in Low Earth Orbit

A low complexity statistical method is presented for fast re-acquisition of Global Position System signals in Low Earth Orbit. Based on off-line estimates of the mean and variance of the Doppler shift drift, the two sided confidence intervals of the phase and frequency, according to an initial search bin and time, is derived. A square region of confidence is derived from the confidence intervals which reduces the search space and, hence, also the re-acquisition time. Given a 99% confidence interval the derived prediction method can reduce the search space size for the considered case for up to approximately 330 seconds without any misses. For shorter time spans the method is able to reduce the search space size significantly and in the considered case two order of magnitude reduction in search space size is achieved at a prediction time of 20 seconds.