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An instrument using time signals from the Navy Navigation Satellite System (Transit) to derive precise time referenced to the U.S. Naval Observatory (USNO) master clock is described. The two sources of system time error, receiver detection error and spacecraft timekeeping error, are analyzed. Performance data from production equipment tested at USNO are given. A cooperative program between USNO and the control agency to improve the spacecraft timekeeping is outlined. Phase One of this program is underway, and projected results are analyzed. System accuracy is forecast to be 3–5 μs rms when this program is completed.