A5008325867- Advanced Frequency and Time Standards
- GNSS positioning and interference
- Scientific Measurement and Uncertainty Evaluation
- Atomic and Subatomic Physics Research
- Radioactive Decay and Measurement Techniques
- Cold Atom Physics and Bose-Einstein Condensates
- Geophysics and Sensor Technology
- Inertial Sensor and Navigation
- Geophysics and Gravity Measurements
- Ionosphere and magnetosphere dynamics
- Astronomical Observations and Instrumentation
- Advanced Electrical Measurement Techniques
- Time Series Analysis and Forecasting
- Network Time Synchronization Technologies
- Non-Invasive Vital Sign Monitoring
- Spectroscopy and Laser Applications
- Target Tracking and Data Fusion in Sensor Networks
- Astro and Planetary Science
- Advancements in PLL and VCO Technologies
- Sensor Technology and Measurement Systems
- Hemodynamic Monitoring and Therapy
- Analytical Chemistry and Sensors
- Advanced Fiber Laser Technologies
- Historical Astronomy and Related Studies
- History and Developments in Astronomy
Bureau international des poids et mesures
2018-2024
Istituto Nazionale di Ricerca Metrologica
2009-2018
Torino e-district
2009-2011
University of Turin
2002-2010
Ferrari (Italy)
1994-2006
Istituto Nazionale di Fisica Nucleare, Galileo Galilei Institute for Theoretical Physics
1991-2006
Laboratoire National de Métrologie et d'Essais
2006
Information Management Services
2006
Solvay (Belgium)
2006
Eni (Italy)
2006
Abstract This paper outlines the roadmap towards redefinition of second, which was recently updated by CCTF Task Force created in 2020. The main achievements optical frequency standards (OFS) call for reflection on but open new challenges related to performance OFS, their contribution time scales and UTC, possibility comparison, knowledge Earth’s gravitational potential ensure a robust accurate capacity realize definition at level 10 −18 uncertainty. mandatory criteria be achieved before...
The clock errors are modeled by stochastic differential equations (SDE) and the relationships between diffusion coefficients used in SDE Allan variance, a typical tool to estimate noise, derived. This relationship is fundamental when mathematical model used, for example Kalman filter, noise estimation, prediction activities.
The three-cornered hat method used for evaluating the individual noise contributions of three frequency standards in a stability measurement is reexamined. hypothesis uncorrelation not assumed priori, as it considered cause negative estimated variances. introduction covariances measured data, together with proposal suitable optimization criterion, allows one to estimate complete covariance matrix standards, ensuring its positive definiteness.< <ETX...
Abstract The relationship and the mutual benefits of timekeeping Global Navigation Satellite Systems (GNSS) are reviewed, showing how each field has been enriched will continue to progress, based on progress other field. role GNSSs in calculation Coordinated Universal Time (UTC), as well capacity provide UTC time dissemination services described, leading now a transfer accuracy order 1–2 ns. In addition, fundamental atomic clocks GNSS positioning is illustrated. paper presents review current...
The statistical generation of an accurate, stable and reliable time scale from a clock ensemble calls for efficient algorithm. Here we present comparative study which points out conceptual differences similarities between two different types algorithm used worldwide:
The estimation of individual instabilities N clocks, when only differences clock readings are available, is examined without any a priori assumption about the lack correlation between clocks. instability clocks described by × covariance matrix R but (N - 1) S referred to N-th may be estimated directly from measurements. not unique solution domain limited positive definiteness R. features this analysed and conditions for validity uncorrelation hypothesis established. modifications domain,...
A mathematical model for the clock phase and frequency deviation based on theory of stochastic differential equations (SDEs) is discussed. In particular, we consider a that includes what are called `white random walk noises' in time metrology, which give rise context to Wiener an integrated process phase. Due particular simple expression functions involved exact solution exists, determine it by considering wider theoretical context, suitable generalizations more complex instances. Moreover,...
The Ornstein-Uhlenbeck process is presented with its main mathematical properties and original results on the first crossing times in case of two threshold barriers.The interpretation as filtered white noise, stationary spectrum, Allan variance are also for easiness use time frequency metrology field.An improved simulation scheme evaluation passage between barriers introduced.
We present and discuss the dynamic Allan variance, a measure of time-varying stability an atomic clock. First, variance is mathematically defined, then its behavior extensively tested on simulated experimental data. The results prove validity effectiveness proposed new tool.
In this paper we use a mathematical model based on stochastic differential equations to predict the behaviour of atomic clocks. We consider several different cases with deterministic and random signatures obtain best clock prediction together its uncertainty. The results given by our are compared traditional method extrapolating from past data.
This article reviews applications of the Kalman filter to atomic timing. The objectives are twofold - present diverse and concepts in a consistent fashion, both regard notation mathematical concepts. develop key ideas tutorial form by introducing basic then applications.we apply clock estimation, monitoring, time-scale definition. Furthermore, GPS composite algorithm along with numerical simulations is described. Finally, advantages criticalities application timing, highlighting issues that...
Due to their stability atomic clocks represent the core of navigation systems such as GPS and future European Galileo system. To identify possible anomalies, it is fundamental detect when clock varies with time. The dynamic Allan variance (DAVAR) makes this monitoring process possible. We extend DAVAR case a time series missing data, we analyze presence periodic behaviors, two common phenomena in space clocks.
Frequency jumps are common anomalies in atomic clocks aboard navigation system satellites. These anomalous behaviors must be detected quickly and accurately to minimize the impact on user positioning. We develop a detector for frequency based Kalman filter. Numerical simulations show that is fast, with high probability of detection low false alarms. It also has computational cost because it takes advantage recursive nature Therefore, can used applications which little power available, such as
In this paper, the problem of identifying variations in nature atomic clock noise is addressed. Two methods are proposed. One method based on a generalized likelihood ratio test (GLRT), and other dynamic Allan variance (DAVAR), which representation instantaneous stability that able to point out possible nonstationary behaviors. Both efficiently track experimental data and, thus, appear as suitable tools for detection anomalies
In recent years, many national timing laboratories have installed geodetic global positioning system (GPS) receivers together with their traditional GPS/GLONASS common view (CV) and two way satellite time frequency transfer (TWSTFT) equipment. A method called precise point (PPP) is in use the community allowing recovery of GPS receiver position, clock phase tropospheric delay by taking advantage International GNSS Service (IGS) products. Natural Resources Canada (NRCan) has developed...
Statistical and mathematical tools useful for atomic clock applications are reviewed to offer the reader an overview of past work along with still in progress time scale algorithms.
The Galileo In-Orbit Validation Element (GIOVE) is an experiment led by the European Space Agency (ESA) aimed at supporting on-going implementation of Galileo, global navigation satellite system (GNSS). Among objectives GIOVE Mission are validation and characterization on-board clock technologies. current baseline technologies for clocks rubidium atomic frequency standard (RAFS) passive hydrogen maser (PHM). Both have been validated qualified on ground now being further in a representative...
The ability of the Allan variance (AVAR) to identify and estimate typical clock noise is widely accepted, its use recommended by international standards. Recently, a time-varying version called Dynamic (DAVAR) was suggested exploited.
When an anomaly occurs in atomic clock, its stability and frequency spectrum change with time. The variation time of the can be evaluated dynamic Allan variance. described spectrogram, a time–frequency distribution. We develop method that uses variance spectrogram to detect identify typical anomalies clock. apply simulated data.
The ac-Stark shift (or light shift) is a fundamental aspect of the field/atom interaction arising from virtual transitions between atomic states, and as Alfred Kastler noted, it real-photon counterpart Lamb shift. In rubidium frequency standards (RAFS) flying on Global Positioning System (GPS) satellites, plays an important role one major perturbations defining RAFS' frequency: rf-discharge lamp in RAFS creates signal via optical pumping simultaneously perturbs atoms' ground-state hyperfine...
Abstract In order to fulfil its mission ensure and promote the global comparability of measurements, BIPM operates laboratories in fields physical metrology, ionizing radiation, chemistry time. These act as centres for scientific technical collaboration between Member States providing capabilities international measurement comparisons on a shared cost basis. They coordinate national standards agreed be highest priority, they establish maintain appropriate reference use basis key at level...
The Kalman filter is a very useful tool of estimation theory, successfully adopted in wide variety problems. As recursive and optimal technique, the seems to be correct also for building precise timescales, various attempts have been made past giving rise, example, TA(NIST) timescale. Despite promising expectations, completely satisfactory implementation has never found, due intrinsic non-observability clock time readings, which makes problem underdetermined. However, case applied difference...
A test of the position invariance (LPI) principle embodied in Einstein equivalence (EEP) has been performed via a ``null'' gravitational redshift experiment. The rate magnesium frequency standard compared with that cesium reference clock searching for dependence on solar potential during period 430 days. Because Earth's orbital motion experiment, laboratory had peak-to-peak variation 6.7\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}10}$, allowing us to set an upper limit...
This work presents a study of the determination uncertainties in [UTC − UTC(k)] needed for publication Bureau Inernational des Poids et Mesures's (BIPM's) Circular T and Key Comparison Database, as required by Mutual Recognition Arrangement. In first part paper, an analytical solution based on law propagation uncertainty is derived. second part, verified numerically using software used BIPM generation UTC.
In recent years, many national timing laboratories have installed geodetic Global Positioning System receivers together with their traditional GPS/GLONASS Common View and Two Way Satellite Time Frequency Transfer equipment. Many of these operate continuously within the International GNSS Service (IGS), data are regularly processed by IGS Analysis Centers. From its global network over 350 stations Centers, generates precise combined GPS ephemeredes station satellite clock time series referred...