Resources for Time & Frequency Metrology
With the advent of atomic frequency standards (atomic clocks), it has become possible to measure frequencies with extremely high precision and accuracy. The definition of frequency has been referenced to a microwave transition of the cesium atom, and it is routinely measured to a few parts in 10-16 by individual laboratories. On shorter scales, frequency standards under development are already capable of measuring frequencies to precisions of 10-18 and even below. For these reasons frequency measurements may well be the most precise and accurate types of measurements ever made by humankind. Time, as the integral of the frequency, is operationally measured at the level of nanoseconds over long distances, and at the several picosecond level within laboratories.
The construction of atomic clocks is an experimental art drawing heavily on quantum mechanics, relativity, and statistics. Conversely, data from atomic clocks has provided important tests of physical theories, and inspired the development of new mathematical and statistical techniques. The applications to atomic clock development are paralleled by the development of new ways to convert time signals from one form to another, such as from microwave to optical, and by the development of the electronic infrastructure and mathematical techniques for combining and differencing data from nearby clocks.
The high precision and accuracy of atomic clocks has also brought about the need for improved long-distance clock comparisons, referred to as time transfer (time and frequency transfer). Long-distance time transfer is operationally carried out by use of geostationary satellites as well as Global Navigational Satellite Systems, while fiber-optic and free-space time and frequency transfer are under active development and finding more and more operational applications. Conversely, GNSS rely on atomic clocks and their characterization for their continuous day-by-day operations.
The field of time and frequency metrology has followed a kind of Moores Law in which the accuracy, frequency, and stability of its techniques have improved by orders of magnitude every few years. We expect this to continue at least for the next decade.
Short-duration Training Events
- European Frequency and Time Seminar, http://www.efts.eu/dokuwiki/doku.php?id=current:00_start
- GNSS Summer School, http://www.gnss-pnt.org/SummerSchool2017/programme.php
- NIST Time and Frequency Seminar, search for event here: http://www.nist.gov/news-events/events
- NICT T&F Activites Web Page: http://www2.nict.go.jp/sts/lab/activities.html (Google Chrome can translate into English)
- Asia-Pacific Workshop on Time and Frequency, http://www2.nict.go.jp/sts/lab/ATF/index.html
- Conference on Precision Electromagnetic Measurements, https://ieeexplore.ieee.org/xpl/conhome.jsp?punumber=1000590
- European Forum on Time and Frequency and associated tutorials, http://www.eftf.org
- International Frequency Control Seminar and associated tutorials (IFCS 2016.org.) https://ieeexplore.ieee.org/xpl/conhome.jsp?punumber=1000296
- Institute of Navigation Precise Time and Time Interval Meeting (ION-PTTI), and associated tutorials, www.ion.org
- URSI General Assemblies and other meetings, www.ursi.org
- Institute of Electrical and Electronic Engineers (IEEE) http://www.ieee-uffc.org/frequency-control
Open Source Publications
- Institutions whose web pages host an extensive set of open-source publications: NIST (www.nist.gov), BIPM (www.bipm.org)
- PTTI papers prior to 2013 available from behind a paywall to the Institute of Navigation and as open-source from https://tycho.usno.navy.mil/ptti/
- Documents from APMP TCTF Technical Workshop on Guidelines for CMC (Tokyo, Japan 2011): http://www2.nict.go.jp/sts/lab/CMC2011/workshop/documents.html
Books at Graduate Level and above
- TIME, From Earth Rotation to Atomic Physics, D. McCarthy and K. Seidelmann, 2009, Wiley-VCH Press
- The Measurement of Time: Time, Frequency, and the Atomic Clock, C. Adouin and B. Guinot, 2001, Cambridge University Press
Refereed Professional Journals
- Metrologia, www.iopscience.org/met
- Transactions of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society (T-UFFC), http://www.ieee-uffc.org/publications/tr/
- IEEE Transactions on Instrumentation and Measurement, (http://ieeexplore.ieee.org)
- IEEE Distinguished Lecturer http://www.ieee-uffc.org/main/distinguished-lecturer-reports.asp
- The French national time and frequency network in French: http://first-tf.fr/ and in English http://first-tf.com