Signal Deformations On Nominally Healthy GPS Satellites

This paper describes the collection and analysis of real dat from twenty-four current, nominally healthy GPS satellite s in the context of the ICAO second-order step (2OS) fault model. A simple but novel method is presented for averaging multiple C/A code epochs together, using Doppler prediction to achieve essentially open-loop synchronous sampling of the code waveform. This yields a clean picture of the C/A code edge transitions. Two different methods are then used to estimate the digital failure mode parameter, ∆, that characterizes each observed satellite within the context of the 2OS model. The results of this analysis are grouped by satellite block and, separately, by the type of frequency standard in operation at the time of measurement. Finally, the potential implications of these mea surements on integrity and continuity are discussed.