Integrity Analysis of GPS Signal-in-Space Error

Abstract

The space segment failure is one of the main sources of system integrity risk. This paper proposes an integrity analysis method to analyze the integrity risk of signal in space. Firstly, the original data should be preprocessed to calculate measured signal-in-space error. Secondly, the regularity of the errors is estimated by the spectrogram, followed by fitting orbit error with the least squares method based on Fourier series and AR model and fitting clock error with AR model. In order to detect the abnormal values of the signal-in-space errors roughly, the paper set the condition that when the difference between the original error and the fitted values is more than 4.42 times the standard deviation of fitted values, the abnormal data may exist. Then it’s necessary to identify specific abnormal factors which conclude satellite unhealthy, duplicate broadcast ephemeris and ephemeris missing to statistics the according abnormal rate. The simulation results of the measured data of different type in-orbit satellite which is from 2002 to 2011 show that the abnormal rate of signal in space is 10⁻⁴/h, which meet the index that three satellites may fault every year, therefore the analysis method is verified to be effective.