Cesium beam phase and frequency measurements using GPS time transfer techniques

The authors describe a technique of GPS (Global Positioning System) time transfer that uses direct communication with the satellite. Both the TTR5 GPS time transfer receiver model and the Hewlett Packard HP cesium beam references were found to perform exceptionally well during a 40-day period. No large frequency changes of the HP cesium during this period were observed. With these devices, it was possible to monitor not only the behavior of the ground reference but also to obtain detailed insights into the performance of the in-orbit spaceborne cesium and rubidium clocks. Moreover, it was possible to observe in near real time the effects of ground `tuning´ of the GPS time