3.3 A novel Robust and Precise Timing Facility for Galileo

Abstract

A fundamental component in each Global Navigation Satellite System is the timing facility, which is responsible for the synchronization of all elements within the ground segment as well as for the satellites in space. Different concepts exist to provide a time scale that fulfils all requirements, e.g. master clock principle, weighted clocks or composite clock algorithm. In the European Global Navigation Satellite System Galileo, the so-called Precise Timing Facility (PTF), located in Oberpfaffenhofen, Germany, and Fucino, Italy, has the task to provide the Galileo System Time (GST). The actual published design of the PTF depends on a master clock principle and is therefore sensitive to failures of individual units within the GST generation [1].At DLR Galileo Competence Center we propose an alternative design for such a timing facility, which is called Robust Precise Timing Facility (RPTF). The focus of the concept is on mitigating technical vulnerabilities and increasing the tolerance to the failure of any of the components of the existing PTF.In this paper we present the concept, current status and future plans for such a RPTF to generate robust system timescales for the next generation of the European satellite navigation systems. The aim is to build, test and characterize the RPTF under the aspect of a 24/7 operational service. The key element is the combination of all the individual atomic clocks in the facility via the composite clock approach to generate a weighted average, the so-called Implicit Ensemble Mean (IEM), and to provide redundancy and test opportunities in case of hardware and software failures.