GPS Signal-in-Space Integrity Performance Evolution in the Last Decade

Knowledge of the Global Positioning System (GPS) signal-in-space (SIS) anomalies in history has a great importance for not only assessing the general performance of GPS SIS integrity but also validating the fundamental assumption of receiver autonomous integrity monitoring (RAIM): at most one satellite fault at a time. The main purpose of this paper is to screen out all potential SIS anomalies in the last decade by comparing broadcast ephemerides and clocks with precise ones. Validated broadcast navigation messages are generated from 397,044,414 navigation messages logged by on average 410 International GNSS Service (IGS) stations during the period 6/1/2000-8/31/2010. Both IGS and National Geospatial-Intelligence Agency (NGA) precise ephemerides/clocks are used as truth references. Finally, 1256 potential SIS anomalies are screened out. These anomalies show an improving SIS integrity performance in the last decade, from tens or hundreds of anomalies per year before 2003 to on average two anomalies per year after 2008. Moreover, the fundamental assumption of RAIM is valid because never have two SIS anomalies or more occurred simultaneously since 2004.