GPS TIME TRANSFER

Over the past ten years GPS satellites have become the principal tool for national and international comparisons of atomic clocks. Using GPS, time transfer is now ten times more accurate than it used to be using LORAN-C. For the first time, the best frequency standards in the world have been compared in a way which exploits their full level of performance. The present accuracy of GPS time transfer is of the order 10-20 ns for intercontinental distances and 2-3 ns within one continent. Although many improvements have been introduced during the past decade, the next should bring still further improvements leading to an ultimate accuracy at the subnanosecond level.