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23ème Conférence générale des poids et mesures Rapport du Comité Consultatif

23ème Conférence générale des poids et mesures Rapport du Comité Consultatif du Temps et des Fréquences Luc ERARD Président du CCTF. Sommaire. TAI/UTC Comparaisons d’horloges Comparaisons clés (KC) Groupes de travail (WG) Développements futurs. International time scales TAI and UTC.

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23ème Conférence générale des poids et mesures Rapport du Comité Consultatif

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  1. 23ème Conférence générale des poids et mesures Rapport du Comité Consultatif du Temps et des Fréquences Luc ERARD Président du CCTF 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  2. Sommaire • TAI/UTC • Comparaisons d’horloges • Comparaisons clés (KC) • Groupes de travail (WG) • Développements futurs 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  3. International time scales TAI and UTC • The BIPM is responsible for realizing, maintaining and disseminating the international reference time scales; • International time keeping is the result of the cooperation of many laboratories distributed worldwide; • The efforts of the community dealing with time metrology are focused towards the construction of time scales adapted to the most demanding applications and requiring: • Continuity • Reliability • Accessibility • Frequency stability of order 10-15 • Frequency accuracy of order 10-15 (traceability to the SI second) 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  4. International time scales TAI and UTC TAI • Atomic scale (14th CGPM,1971), Continuous • Calculated in post-real time (~10 days after the last date of data), Frequency stability (0.5 x 10-15 @40 days) • Unit: SI second, Frequency accuracy (~10-15) • It has no representations through clocks, not disseminated • It has scientific applications and provides a frequency reference 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  5. International time scales TAI and UTC UTC (coordinated universal-time) • Atomic time scale (ITU-R, Rec. 460, 1970; 460-1, 1974) • Continuous with one-second steps at irregular intervals (leap second) • Differs from TAI in an integer number of seconds (33 s at present) • Post-processed (~10 days after last date of data) • Unit: SI second, Frequency stability and accuracy (idem TAI) • Represented by clocks • Local approximations UTC(k), [UTC-UTC(k)] < 100 ns (recomm.) • Disseminated • Circular T, CCTF-K001.UTC (delayed time), Time signals (real time approximations) • Legal applications • Basis of legal times 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  6. TAI/UTC ALGOS (algorithm for calculation) Time and frequency differences Clock data data Time transfer EAL • Optimized frequency stability • No constrained to be accurate in frequency + PFS data Frequency corrections • Optimized frequency stability • Accurate in frequency TAI + (-n x s) UTC IERS leap second announcements 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  7. 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  8. 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  9. PRIMARY FREQUENCY STANDARDS (PFS) • 11 regularly reporting measurements to BIPM • from 6 time National metrology laboratories • 7 are Caesium fountains • frequency accuracy 0.5 to 4 × 10-15 • improve the accuracy of the TAI 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  10. Typical characteristics of the calibrations of the TAI frequency provided by the different primary standards in 2006 Reports of operation of PFS are regularly published in the BIPM Annual Report 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  11. Model of instability of EAL is used to include PFS calibrations in a month of calculation of Circular T normalized filter coefficients (“weights”) that depend on uncertainty of the PFS evaluation distance between the intervals of evaluation and calculation instability of EAL Need of a refined model (Arias&Petit, 2005) negative filter coefficients stability of PFS better than that of EAL New model adopted since 2005.7 Improvements in the algorithm 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  12. Improvements in the algorithm 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  13. Comparaisons clés (KC) • CCTF-K001.UTC • Published since January 2005 • Reference value is UTC • Updated monthly • CCTF-K002.FREQ • Under construction • Coordination between CCTF WG on the MRA and the BIPM 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  14. 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  15. Groupes de travail (WG) • WG on TAI • Symposium on time scales algorithms in 2008 (San Fernando) • GPS CV to AV (with a pivot laboratory) • WG on Global navigation satellite system: means of implementing the use of carrier phase for time and frequency transfer in TAI 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  16. Groupes de travail (WG) • WG on TWSTFT: • Negociation of links with Intelsat • WG on Coordination of the Development of Advanced Time and Frequency Transfer Techniques • WG on Primary frequency standard: • Workshop in Geneva, 2007 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  17. Groupes de travail (WG) • CCL/CCTF WG on frequency standards: • Proposal for radiations suitable for secondary representations of the second; • Proposal for radiations for the practical realization of the meter; > Single list of radiations • WG on CIPM MRA: still missing representatives of RMOs 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  18. Développements futurs Improvement of the time scales • Better clocks: commercial and PFS, frequency prediction, clock weighing procedure,… • Clock comparison: less noisy techniques, accurate frequency transfer techniques GPS, TWTSTF, Galileo, ... 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  19. Développements futurs Optical clocks Gill & Riehle 2006 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

  20. Développements futurs • Comb technology for frequency comparisons (microwave to optical); • Optical fiber links for comparison; • Use of secondary representation of the second for TAI; • Redefinition of the second?? 23ème Conférence générale des poids et mesures Paris, 12-16 novembre 2007

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