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Starting from the month of January 2020, the official Italian time scale, UTC(IT), and its hot backup are generated by the new time-scale algorithm described in [1], with the robust and fully automated procedure developed at the Italian National Metrological Institute, INRiM, presented in [2]. Specifically, the hydrogen masers generating the master and backup time scales are independently steered with respect to UTCr, then the backup time scale is aligned in phase to the master one. The monitoring function generates daily reports on the status and performances of algorithms and time scales, as well as warnings and alarms if an anomaly is detected, allowing for a prompt human intervention, if it is required. We report on the performances of UTC(IT) during the first months of operation of the new time-scale algorithm, also discussing the robustness of the automated procedure, the effectiveness of the monitoring function, and the interventions required during such period. Moreover, we report on a seamless switch from the master to the backup time scale, on the replacement of the hydrogen maser generating the backup time scale, and on the dependence of the time scale performances on the master clock behavior, showing how the stability of the time scale is improved after switching from a more noisy to a less noisy maser. The fully automated procedure for the generation of UTC(IT) proved its efficiency and currently guarantees state-of-the-art performances to the Italian time scale, at the same time reducing the effort required to the staff of INRiM’s time laboratory for its maintenance. References [1] L. Galleani, G. Signorile, V. Formichella and I. Sesia, “Generating a real-time time scale making full use of the available frequency standards,” Metrologia 2020, in press. [2] V. Formichella, G. Signorile, T. T. Thai, A. Perucca, E. Cantoni, M. Sellone, A Mura, I. Sesia and F. Levi, “Reliable and Robust Real-Time Time Scale Generation: Developments and Experimental Results at INRiM,” in proc. PTTI 2020.

In the frame of the EGNOS Service Performance Monitoring Support to GSA (SPMS), four time laboratories (OP, INRIM, CNES and ORB) are responsible for the monitoring of the time scales broadcast by EGNOS. These are in particular the EGNOS Network Time (ENT) and the difference ENT?UTC(OP) which is broadcast using a specific message type (MT#12). The monitoring concerns both the stability and the accuracy of these time scales. This paper presents the results of the first year of ENT and MT#12 monitoring. It also explains why different approaches to get ENT can lead to biases of few ns in the results. Finally the paper presents a comparison between the EGNOS Timing performances and the U.S. augmentation system WAAS timing performances.

During 2015-2016, a European Consortium of 15 partners from 8 different countries, developed the DEMETRA (DEMonstrator of EGNSS services based on Time Reference Architecture), a project funded by the European Union in the frame of the Horizon 2020 program. This project aims at developing and experimenting time dissemination services dedicated to specific users like traffic control, energy distribution, finance, telecommunication, and scientific institutions. Nine services have been developed. These services provide time dissemination with accuracy levels from millisecond to the sub-ns, and also additional services like certification, calibration, or integrity. Five of these services are based on the European GNSS. After a development phase (see PTTI 2016 presentation) the full DEMETRA system has been working during six months for demonstration. The paper will report about the experimentation results, showing performances and limits of the proposed time dissemination services, aiming to foster the exploitation of the European GNSS for timing applications.

In Global Navigation Satellite Systems (GNSS), atomic clocks are fundamental for their excellent stability. Being the distance measured from the time, any error on the measure of time leads to an error in the positioning: accurate and stable atomic clocks need to be employed on board satellites. Hence, the on board clock behaviour has to be continuously monitored and any malfunctioning has to be immediately detected. In this work, we illustrate a software tool developed at the National Institute of Metrological Research (INRIM) for GNSS clock characterization and monitoring. In particular we focus on the functionality of frequency drift estimation and removal, including the uncertainty evaluation. Actually, the frequency drift evaluation and the monitoring of its evolution over time is extremely important in GNSS applications to ensure the adequacy of the timing system to the integrity requirements of the positioning service. The software has been optimized for space clock data, which are different from the ones from timing laboratories, since often present missing data and outliers. The tool allows to easily handle satellite clock data, and get a quick estimate and graphic representation of clock key parameters, such as the clock frequency drift.

In Global Navigation Satellite Systems (GNSS) the user's position is determined measuring the time of flight of the signals broadcast from satellites, which is proportional to the distance between the user and each satellite of the constellation. Time and frequency metrology has an essential role in satellite navigation systems: since a distance can be measured from a time, any error on the measure of time leads to an error on the user's position. Hence, it is fundamental to have precise and stable atomic clocks on board satellites. Therefore the on board clock behaviour has to be continuously monitored and any malfunctioning has to be detected immediately to ensure the adequacy of the timing system to the positioning service and users' needs. This paper will describe the main methodologies for characterization of onboard clocks and their implementation in a robust software developed at INRIM and also used in the framework of the European project Galileo.