William Konyk, National Geospatial-Intelligence Agency

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Given the importance of GPS multiple organizations regularly process satellite position and clock data to create publicly available, precise ephemeris products. Underlying each product is a timescale that describes the satellite clock biases. This work uses what amounts to a common view time-transfer method on three years’ worth of data to compare the timescales of the IGS (representing the scientific standard), the NGA (representing the official standard), and seven component IGS analysis centers. Included are basic details of how each center estimates clock states, an analysis of time and frequency offsets, and the absolute and relative stabilities of the timescales.