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Time and Frequency Comparisons Between Four European Timing Institutes and NIST Using Multiple Techniques



Andreas Bauch, Joseph Achkar, R Dach, R Hlavac, Luca Lorini, Thomas E. Parker, G. Petit, P Uhrich


Istituto Elettrotecnico Nazionale Galileo Ferraris (IEN), National Institute of Standards and Technology (NIST), National Physical Laboratory (NPL), Laboratoire National de M¿trologie et d¿Essais ¿ Observatoire de Paris / Syst¿mes de R¿f¿rence Temps Espace (OP), and Physikalisch-Technische Bundesanstalt (PTB) performed an intense comparison campaign of selected frequency references maintained in their laboratories during about 25 days in October/November 2004. The active hydrogen maser reference standards used at all laboratories served at the same time as frequency references for the institutes¿ fountain frequency standards. The fountains of IEN, NPL, and OP were operated for most of the time during the same period, and results of the fountain comparisons are given in an accompanying paper. Three techniques of frequency (and time) comparisons were employed. Going beyond the standard procedures, two-way satellite time and frequency transfer was performed in an intensified measurement schedule of 12 equally spaced measurements per day. The data of dual frequency geodetic GPS receivers were processed to yield an ionosphere-free linear combination of the code observations from both GPS frequencies, typically referred to as TAI P3 analysis. Last but not least, the same GPS raw data were separately processed allowing GPS carrier-phase based frequency comparisons to be made. These showed the lowest instability at short averaging times of all of the methods. The instability was at the level of 1 part in 1015 at one-day averaging time, similar to what was achieved with TWSTFT. The GPS TAI P3 analysis is capable of giving a similar quality of data provided that averaging over two days or longer is acceptable. The analysis presented here shows that all techniques provide the same mean frequency difference between the standards involved within the measurement uncertainty of a few parts in 1016.
Proceedings Title
19th European Frequency and Time Forum
Conference Location
Besancon, FR
Conference Title
European Frequency and Time Forum


Bauch, A. , Achkar, J. , Dach, R. , Hlavac, R. , Lorini, L. , Parker, T. , Petit, G. and Uhrich, P. (2005), Time and Frequency Comparisons Between Four European Timing Institutes and NIST Using Multiple Techniques, 19th European Frequency and Time Forum, Besancon, FR, [online], (Accessed June 23, 2024)


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Created March 21, 2005, Updated February 17, 2017