Long baseline clock comparison with multichannel GPS time receivers

The paper shows how spread-spectrum signals can be used to allow the worldwide timing community to compare atomic clocks on a very precise level. For this a new generation of multichannel GPS time receivers has been applied. At the present time the international timing community has access to multichannel time receivers using the commonly known satellite navigation systems GPS and GLONASS. The new generation of time receivers offers a great potential to time users. One advantage is the possibility of almost continuous ultra-precise comparison of remote clocks. The implementation of an international tracking schedule to avoid, e.g., the GPS´s selective availability can be done very easily with no need for schedule updates. A user can also perform studies to investigate short- and long-baseline links and changing of various processing parameters. If one uses a high rate data, investigations can be done in much more detail. This also leads to the application of carrier phase observables. The paper explains the clock comparison technique and necessary hardware; and gives a statistical analysis, with the goal of obtaining the best estimates of the clock offsets between the two remote clocks. Using well established statistical analysis techniques, very good results can be achieved when comparing clocks located within the same region on Earth, and for comparing clocks at great distances from each other. Such receivers will certainly have a large impact for future clock synchronization, and, despite the good results that have been obtained to date, far more investigatory work is required