Tutorials
Join us on Monday, April 20, 2026, for an exclusive series of tutorials delivered by renowned lecturers on-site at the ESA-ESTEC Campus. This is your chance to engage directly with experts, ask questions in person, and deepen your knowledge in an interactive setting.
All tutorials will be professionally recorded and uploaded to the conference’s online platform shortly after the event. Registered participants - both virtual attendees and in-person tutorial participants - will enjoy 30 days of on-demand access to revisit sessions or catch up on any lectures they missed.
Please note: Live streaming will not be available.
| Time | Track 1 | Track 2 |
| 9:00 - 10:30 | Time Scales: how to practically realize UTC and UTC(k) Patrizia Tavella (BIPM, France) | Universal Optical Synthesis Marco Schioppo (NPL, UK) |
| Coffee Break (30 minutes) | ||
| 11:00 - 12:30 | GNSS applications in T&F Daniele Rovera (TFSol, France) / Pascale Defraigne (ROB, Belgium) | Chip scale devices for T&F John Kitching (NIST, USA) |
| Lunch Break (1hrs 30 minutes) | ||
| 14:00 - 15:30 | Fiber links and fiber sensing Cecilia Clivati (INRIM, Italy) | Optical Clocks Christian Lisdat (PTB, Germany) |
| Coffee Break (30 minutes) | ||
| 16:00 - 17:30 | Low Phase Noise Oscillators Jeremy Everard (York University, UK) | T&F metrology in Space: clocks and T&F transfer in GNSS Pierre Waller (ESA, The Netherlands) |
Patrizia Tavella
Time Scales: how to realize UTC and UTC(k)
Timekeeping in an important international need that calls for accurate and reliable coordination. The international standard time, the Coordinated Universal Time (UTC), is computed by the BIPM based on the contribution of about 450 atomic clocks kept in about 85 laboratories all over the world. Each laboratory contributes with its clocks and primary or secondary frequency standards (PSFS), compared through GNSS or TWSTFT techniques. All these measures enter in UTC with a weight aiming to optimize the long-term stability and accuracy of UTC.
Each laboratory “k” realizes a real time approximation of UTC, which is called UTC(k), and it is often the basis of civil and legal time in the country. Based on the needs and the resources of the laboratory, UTC(k) can be based on a single atomic clock and a GNSS receiver, or can imbed more clocks, PSFS, and different time transfer techniques.
In recent years the Consultative Committee for Time and Frequency (CCTF) has developed tools to support the validation of the UTC data by national laboratories. These capacity building tools available at https://e-learning.bipm.org, developed with the support of the UFFC society and of secondees working at the BIPM, will be introduced together with the algorithm for the computation of UTC.
The role of a national time scale, its coordination with UTC, the applications and needs that are now challenging the international timekeeping as the continuity of UTC and the growing need of synchronization by industries will be presented.
Biography
Patrizia Tavella, degree in Physics and PhD in Metrology, is the Director of the Time Department of the Bureau International des Poids et Mesures and executive secretary of the Consultative Committee for Time and Frequency, after 30 years at the Italian Metrology Institute INRIM. Her main interests are mathematical and statistical models applied to atomic time scales. She was deeply involved in the development of the European Navigation System Galileo.
Marco Schioppo
NPL
Universal Optical Synthesis
Ultrastable light is a key resource in optical frequency metrology, as it sets precision and measurement speed, with important impact on accuracy evaluation of optical frequency standards. In this tutorial, we will introduce the fundamentals to produce ultrastable light, presenting the key components and techniques at the base of the operation of ultrastable lasers, based on ultrastable optical reference cavities, at room temperature and cryogenic. We will discuss how to distribute the stability of an ultrastable laser to multiple wavelengths in the optical domain, using optical frequency combs, with minimal loss of coherence. Different dissemination architectures will be introduced, highlighting figures of merit and practical advantages and disadvantages.
Biography
Marco Schioppo is a principal scientist leading the development of state-of-the-art ultrastable lasers at NPL. He closely works with the team operating the frequency combs at NPL to realise the so called “Universal Synthesiser”, a system capable of disseminating ultrastable light to all the optical atomic clocks at NPL, therefore supporting high stability and high accuracy comparisons of such systems. Marco joined NPL in 2017, after completing three years of postdoctoral research on the development of ultrastable lasers for the Yb optical lattice clock at NIST, in Boulder (CO), USA. He gained his PhD degree on a transportable Sr optical lattice clock at the University of Florence in Italy, where he also previously undertook his undergraduate studies.
Daniele Rovera
TFSol
GNSS applications in Time and Frequency
GNSS applications in Time and Frequency
Global Navigation Satellite Systems (GNSS) allow inexpensive dissemination and remote comparison of time. In common language often we say that the local time is generated by GNSS without specifying in more detail the used technique and this can generate some confusion in time users. In practice some of the GNSS techniques can offer traceability and accuracy at nanosecond level, while other only allows microsecond and are not really traceable. In this tutorial the pro and the cons of several GNSS time transfer/dissemination are presented together with some information on calibration techniques allowing ns level accuracy. An example of the implementation of a local time scale and his GNSS link to TAI will also be presented.
Biography
Giovanni Daniele Rovera was born in Paesana, Italy on February 22 1950. He received the degree in electronic engineering from Politecnico di Torino, Torino, Italy in 1981. He began his scientific activity at IEN G.Ferraris (now INRiM), Torino Italy, working on the metastable Magnesium beam frequency standard and on Cesium beam frequency standards. In 1989 he joined the BNM-LPTF (now LTE) at Observatoire de Paris. Retired in 2020 he continues to work as consultant in INRiM, NIST, OCA His research activity includes the realization of primary frequency standards, the measure of the frequency of secondary standards in the infrared and visible region, time transfer by RF and optical techniques.
John Kitching
Chip-scale atomic devices for time and frequency
Chip-scale atomic clocks are now successful commercial products and research within this scientific field continues to be highly active. This tutorial will cover the design, fabrication and performance of chip-scale atomic clocks including frequency stability, size, weight, power and manufacturability. The key physics elements that underlie these instruments will be discussed, as well as the most important application spaces in which these devices are used. Current trends in the area of chip-scale atomic devices will be presented and some speculation for the future will be discussed.
Biography
Dr. John Kitching is the Leader of the Atomic Devices and Instrumentation Group in NIST’s Physical Measurements Laboratory and a NIST Fellow. He received his PhD in Applied Physics from the California Institute of Technology in 1995 and since then has worked in the Time and Frequency Division at NIST. His research interests include miniaturized atomic clocks and sensors, and applications of semiconductor lasers and micromachining technology to problems in atomic physics and frequency control. He and his group pioneered the development of microfabricated “chip-scale” atomic devices for use as frequency references, magnetometers and other sensors. He is a Fellow of the American Physical Society, the IEEE and the National Academy of Inventors and has received many awards for his work including the Department of Commerce Silver and Gold Medals, the 2015 IEEE Sensors Council Technical Achievement Award, the 2016 IEEE-UFFC Rabi Award and the 2014 Rank Prize. In 2023, he was made a Fellow of the National Academy of Inventors for the invention of the chip-scale atomic clock and the chip-scale atomic magnetometer. He has published over 100 papers in refereed journals, has given numerous invited and plenary talks and has been awarded seven patents.
Cecilia Clivati
Fiber links and fiber sensing
Optical fiber links have become the method of choice for remote atomic clock comparisons across continental distances, thanks to their unrivaled resolution. These comparisons are based on the precise interferometric tracking of fluctuations in the fibers’ optical length. Over the past decade, this technology has expanded beyond time-and-frequency metrology, finding applications in quantum physics and distributed fiber sensing for environmental monitoring.
After a brief overview of the main motivations that led to the development of metrological fiber links, we will look into the core principles, with an emphasis on their role in large-scale optical clock comparisons and their integration into the global communications network. We will then explore how these techniques can be repurposed for fiber sensing, with an overview of representative use cases. We will conclude with a look toward future developments and emerging opportunities for these rapidly growing infrastructures.
Biography
Christian Lisdat
Optical Clocks
Aided by the development of ultra-stable lasers, improved time and frequency dissemination methods and advances in other fields, optical clocks have achieved exceptionally high stability and accuracy. These developments lead to the active discussion on a possible redefinition on the SI unit second based on optical clocks. The evaluation of optical clocks is an essential part of this process e.g. by local and remote comparisons. In these, aspects like the correction relativistic effects related by the time variable gravity potential of Earth become more important than before. On the other hand, the sensitivity of clocks to the gravity potential also allows novel applications in Earth observation and geodesy.
In this tutorial, we will first discuss essential ingredients for the success of optical clocks, followed by examples of high-performance optical clocks and their validation by comparisons. In this context, we will investigate possible limitations to clock comparisons in particular related to the relativistic redshift and the gravity potential of Earth. Transportable clocks will be discussed as tool for the remote comparison of optical clocks, providing an alternative to fibre or free-space based methods for time and frequency dissemination. The combination of transportable clocks and these dissemination, however, opens the path to novel geodetic observation capabilities that may provide improved and long-term stable height reference systems that enable better determination of parameters relevant for the monitoring of climate change.
Biography
Dr Christian Lisdat received his diploma and doctoral degree in physics from Universität Hannover, Germany, in 1998 and 2001, respectively, for his work on spectroscopy of small alkali molecules. After a year as postdoc on photoassociation of caesium at Laboratoire Aimé Cotton in Orsay, France, he worked on a joint project between Leibniz Universität Hannover and Physikalisch-Technische Bundesanstalt (PTB), Braunschweig studying ultra-cold calcium molecules. In 2007, he received the venia legendi from the Leibniz Universität and joined PTB as Research Scientist working on optical lattice clocks. Since 2013 he leads the PTB working group optical lattice clocks, in 2023 he became the leader of the department Quantum Optics and Unit of Length at PTB.
Jeremy Everard
Low Phase Noise Oscillators
Oscillators are used in almost all electronic systems. They set the timing of operations and provide the clock for the system. The phase noise, jitter & stability of these oscillators often sets the ultimate performance limit. Oscillators requiring low phase noise are used in mobile phones, communications systems, control, RADAR and navigation systems and also as flywheel oscillators for atomic clocks, particle accelerator systems and Very Long Base Interferometry (VLBI) systems.
This talk will initially discuss the theory and design of a wide variety of oscillators offering the very best phase performance. Feedback and negative resistance theory and design will be covered.
Best design is typically achieved by splitting the oscillator design into its component parts and developing new amplifiers, resonators and phase shifters which offer high Q, high power handling and low thermal and transposed flicker noise.
Oscillator designs include resonators such as: inductor capacitor, crystal, SAW, printed and ceramic transmission line, dielectric and distributed Bragg resonators.
Key features of oscillators and resonators offering the best performances will be shown.
Biography
Jeremy Everard obtained his degrees from King’s College London and the University of Cambridge, UK in 1976 and 1983 respectively. He worked for six years in industry at GEC Marconi Research Laboratories, M/A-Com and Philips Research Laboratories on Radio and Microwave circuit design. At Philips he ran the Radio Transmitter Project Group.
He then taught at King's College London for nine years and became full Professor of Electronics at the University of York in September 1993. He has taught analogue IC design including the internal design of op-amps, switched mode power supplies with magnetic circuits & Class D audio amplifier design, A to D and D to A design, optoelectronics, filter design, Electromagnetism and RF & microwave circuit design.
In September 2007, he was awarded a five-year research chair in Low Phase Noise Signal Generation sponsored by BAE Systems and the Royal Academy of Engineering.
In the RF/Microwave area his research interests include: The theory and design of low noise oscillators; flicker noise measurement and reduction high efficiency broadband amplifiers; high Q printed filters with low radiation loss and broadband negative group delay circuits. In Opto-electronics, research includes: All optical self-routing switches which route data-modulated laser beams according to the destination address encoded within the data signal, ultra-fast 3-wave opto-electronic detectors and mixers and distributed fibre optic temperature sensors.
Recent research involves the development of atomic clocks using Pulsed Optical Pumped (POP), and ultra-low phase noise microwave flywheel oscillator synthesiser chains with micro Hz resolution.
Jeremy was an IEEE Distinguished Microwave Lecturer on oscillators, filters and clocks from 2018 to 2020. Webinar at: https://resourcecenter.mtt.ieee.org/education/webinars/mttweb0630
He has published a book on “Fundamentals of RF Circuit Design with Low Noise Oscillators” (Wiley).
Pierre Waller
Clocks and T&F transfer in GNSS
Clocks and T&F transfer in GNSS
Atomic clocks are at the heart of any GNSS”: this tutorial aims at demystifying this statement by introducing the role of atomic clocks and time transfer in Global Navigation Satellite Systems, and by reviewing how they ultimately contribute to the provision of Position, Navigation and Time services to billionths of users globally. It will introduce the basic classical GNSS system concepts, the main system elements, and how clocks are operated and compared so that the user can determine its position, velocity and time with respect to a given reference and within guaranteed performance levels. The main clock and timing performance requirements will be derived, and their practical implementation both on-board the satellites and in the ground segment will be presented. This will be illustrated with practical examples, notably from the Galileo System. While the main function of GNSS is to provide positioning services globally, they are also de-facto providing simultaneously timing services allowing any user to determine its time and frequency offsets with respect to agreed standard references. In addition, thanks to its global and free availability, GNSS is the unrivalled solution to provide time transfer at the nanosecond level at the global scale. These GNSS time and frequency dissemination and transfer techniques will be introduced, with practical examples in timescale operations and T&F metrology. Finally, this tutorial will review the current limitations and challenges of clocks in classical GNSS and will provide perspectives on current evolutions and future opportunities.
Biography
Pierre Waller received a MSc and PhD in Physics from University of Paris. He started his professional career at Thales in France as RF/microwave engineer. He joined the European Space Research and Technology Centre (ESA/ESTEC) in 2000, where he supported the development of RF/microwave techniques and technologies for various ESA missions. In 2003 he joined the team responsible for the development of the first atomic clocks for Galileo where he was involved in the design, qualification, on-ground testing and in-orbit validation of the clocks for all Galileo satellites. During this period, he also supported the research in new type of clocks and T&F transfer, the development of techniques and tools for the validation of the Galileo System timing performance, and the establishment of the ESTEC T&F Laboratory. He has been member of the EFTF Executive Committee from 2010 to 2017 and of various CCTF Working and Task Groups related to GNSS and T&F transfer. He is currently the Payload Principal Engineer of the ESA Genesis project, a mission in geodesy aimed at improving the accuracy and stability of the International Terrestrial Reference Frame.
ESA Conference Bureau / ATPI Corporate Events
ESA-ESTEC, Keplerlaan 1
2201 AZ Noordwijk, The Netherlands