Analysis of the Long-term Stability of a Homogenous Cesium Standard Ensemble for Future System Time Generation

Kurzfassung

Global Navigation Satellite Systems (GNSSs) are indispensable for numerous daily life applications. They provide essential services for both civil and military uses. Other than enabling global navigation, GNSSs also allow the distribution of a stable time scale used in various sectors such as aviation, ground and maritime traffic, surveying, synchronization of power grids and stock trading activities. Thus, one key element of such systems is the generation of a stable and robust system time, which can be referenced to a global time scale, i.e. Coordinated Universal Time (UTC). There are several different approaches to ensure an appropriate system time for operational systems, like Global Positioning System (GPS) as an example for ensemble system time or Galileo for a master clock approach. In this paper we will present our latest results on composite clock realization with a set of cesium clocks. One of these clocks is used as the UTC realization by DLR. For our composite clock solution, we used a Kalman filter to predict the clock states, integrated differential clock measurements and produced an Implicit Ensemble Mean (IEM). A second Kalman filter was used to calculate the steering commands necessary to align a clock to the IEM of the ensemble. A regulator was used to implement the required steering. Simulation, long term measurements of an ensembles of cesium clocks and the realization of the IEM have been performed over a period larger than 105 s. This demonstration can be seen as the next step of DLR's contribution to UTC with a physical realization of a robust clock ensemble.