ACSER SEMINAR: Precise Time Scales and Navigation Systems

4 August 2016 - 1:00pm to 2:30pm
Seminar Room G3, Electrical Engineering Building (map G17), UNSW Kensington


IEEE Distinguished Lecture: Precise Time Scales and Navigation Systems, the Ultimate Challenge to Time Metrology

Today, atomic clocks enable precision estimates of time and position. Through the use of ultra precise atomic frequency standards, we can form time scales, such as the international time standard Universal Coordinated Time (UTC), capable of dating events with nanosecond accuracy. Similarly, Global Navigation Satellite Systems (GNSS), provide location all over the world with sub-meter accuracy. In timekeeping, as well as in navigation systems, the questions may be similar, but the answers are frequently dissimilar, due to different goals, requirements, technology availability and constraints.

In both cases precision clocks, measuring systems, and a reference time scale are required; in both cases we need to estimate how often the clocks are to be resynchronized and what is the acceptable time error that a clock may accumulate without compromising system performance. We require a mathematical model to predict clock behavior in order to maintain agreement with another reference clock or to ensure updated  navigation messages. We need to understand the “normal” behavior of a clock to be able to quickly identify
anomalies which can lead to incorrect estimates.

The lecture presents the needs of precise Timing and Navigation, explaining the current international timekeeping architectures and the timing systems of the current GNSS, giving insight to the most demanding topics that still challenge Time Metrology.


Dr Patrizia Tavella obtained a degree in physics at the University of Torino (with 110/110 and praise) in 1986. After a scholarship at the Istituto Elettrotecnico Nazionale (IEN) of Torino, in 1992 she got the Doctorate degree in Metrology at the Politecnico of Torino in collaboration with the IEN, and the Bureau International des Poids et Mesures (BIPM) with the thesis "Time scale algorithms: concepts, models and applications”. Part of the work was carried out in collaboration with the BIPM, where she stayed for several months. In November 1989 she accepted a position as physicist at the Istituto Elettrotecnico Nazionale in the Time and Frequency department. In 1997 she obtained, after a national selection, the degree of “senior scientist” (primo ricercatore). From January 2006 IEN merged in the Istituto Nazionale Ricerca Metrologica INRIM. Since Dec 2010 she got a position of “research director” (dirigente di ricerca) after a selection based on scientific achievements.