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

23ème Conférence générale des poids et mesures Paris, novembre 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 –Frequency accuracy of order (traceability to the SI second)

23ème Conférence générale des poids et mesures Paris, novembre International time scales TAI and UTC TAI Atomic scale (14 th CGPM,1971), Continuous Calculated in post-real time (~10 days after the last date of data), Frequency stability (0.5 x 10 days) Unit: SI second, Frequency accuracy (~ ) 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, novembre 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, novembre TAI/UTC ALGOS (algorithm for calculation) Time and frequency differences Clock dataTime transferdata EAL Optimized frequency stability No constrained to be accurate in frequency PFS data Frequency corrections + TAI + (-n x s)UTC Optimized frequency stability Accurate in frequency IERS leap second announcements

23ème Conférence générale des poids et mesures Paris, novembre

23ème Conférence générale des poids et mesures Paris, novembre

23ème Conférence générale des poids et mesures Paris, novembre 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 × improve the accuracy of the TAI

23ème Conférence générale des poids et mesures Paris, novembre 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, novembre Improvements in the algorithm 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

23ème Conférence générale des poids et mesures Paris, novembre Improvements in the algorithm

23ème Conférence générale des poids et mesures Paris, novembre 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, novembre

23ème Conférence générale des poids et mesures Paris, novembre 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, novembre 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, novembre 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, novembre 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, novembre Gill & Riehle 2006 Développements futurs Optical clocks

23ème Conférence générale des poids et mesures Paris, novembre 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??