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Abstract:
The orbit errors, clock errors, and signal-in-space ranging errors of the third generation of BeiDou navigation satellite system (BDS-3) are analyzed by comparing broadcast ephemeris with precise products of long period. The average availability of signal-in-space (SIS) over all BDS-3 satellite is 98.76%, and those with the medium earth orbit (MEO) and inclined geosynchronous orbit (IGSO) satellites are 98.89% and 97.05%, respectively. Due to the inter-satellite link of BDS-3, the percentages of ages of data, ephemeris and ages of data, clock less than one hour increase to 97.34% and 96.85%, respectively. The root mean square (RMS) of the three-dimensional (3D) orbit errors of BDS-3 satellite is 0.57 m. The eclipses and maneuvers of the IGSO satellites have a greater impact on orbit accuracy than those of the MEO satellites. The clock errors of different satellites are remarkably positively correlated. The RMS values of orbit-only, global-average, and worst-case signal-in-space ranging errors (SISREs) of BDS-3 are 0.12 m, 0.57 m, and 1.10 m, respectively, and the actual URA of 2.0 m in the navigation message might be conservative for integrity since it can overbound the 95th percentile of global-average RMS SISRE for most satellites and RMS of the daily worst-case SISRE for all satellites. A more proper distribution is introduced to describe the BDS-3 orbit errors and clock errors. By considering non-zero mean value of actual worst-case SISRE, the standards for SIS integrity for different integrity risk levels are proposed.
