Simulation of the effect of improved ground clocks on GPS timing performance

The GPS system is simulated in three scenarios, so as to estimate how its performance would be improved by more stable ground clocks. One scenario is an approximation to the current system. The second replaces the cesium frequency standards at the monitor sites with masers. The third replaces the masers at the two USNO-controlled monitor sites with atomic fountains. The simplifications exaggerate the differences between the scenarios, and the results suggest that the three scenarios are similar in the timing information as delivered to the user for positioning, but that GPS Time could be more stable with improved clocks. Results are tentative, pending more realistic simulations.