Time and frequency comparisons using radiofrequency signals from satellites

Bauch, A.

doi:10.1016/j.crhy.2015.02.006

Cited by 24 publications

(17 citation statements)

References 24 publications

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“…The frequencies of two Sr lattice clocks between Japan and Germany were compared via two-way carrier phase time and frequency transfer using a geostationary satellite in a first demonstration [56]. The fractional uncertainty of 1.6 × 10 −15 for a measurement time of one day shows that the currently available standard techniques are not capable to support the accuracy and instability of optical clocks in the 10 −18 range.…”

Section: Comparisons Of Optical Clocks Remote From Each Othermentioning

confidence: 99%

“…The frequent comparisons of clocks that are necessary to maintain the International Atomic Time Scale TAI and the International Coordinated Time Scale UTC rely on well-established technologies using radiofrequency signals from and via satellites (see, e.g., [55] in this dossier). The frequencies of two Sr lattice clocks between Japan and Germany were compared via two-way carrier phase time and frequency transfer using a geostationary satellite in a first demonstration [56].…”

Section: Comparisons Of Optical Clocks Remote From Each Othermentioning

confidence: 99%

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Towards a redefinition of the second based on optical atomic clocks

Riehle

2015

Comptes Rendus. Physique

149

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Future redefinition of the second Frequency and time dissemination Mots-clés :Horloges optiques atomiques Étalons de fréquence Redéfinition future de la seconde Diffusion des fréquences et des signaux horairesThe rapid increase in accuracy and stability of optical atomic clocks compared to the caesium atomic clock as the primary standard of time and frequency asks for a future redefinition of the second in the International System of Units (SI). The status of the optical clocks based on either single ions in radio-frequency traps or on neutral atoms stored in an optical lattice is described, with special emphasis on the current work at the Physikalisch-Technische Bundesanstalt (PTB, Braunschweig, Germany). Besides the development and operation of different optical clocks with estimated fractional uncertainties in the 10 −18 range, the supporting work on ultra-stable lasers as core elements and the means to compare remote optical clocks with transportable standards, optical fibres, or frequency ratios is reported. Finally, the conditions, methods and next steps are discussed, which are the prerequisites for a future redefinition of the second. © 2015 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.r é s u m é L'amélioration rapide en termes de précision et de stabilité des horloges atomiques optiques par rapport à l'horloge atomique au césium, qui constitue la référence primaire pour le temps et la fréquence, appelle une future redéfinition de la seconde dans le système international d'unités (SI). L'état d'avancement des horloges optiques basées sur des ions uniques dans des pièges radiofréquence ou sur des atomes neutres confinés dans le réseau optique est décrit, en insistant particulièrement sur le travail en cours à la PhysikalischTechnische Bundesanstalt (PTB, Brunswick, Allemagne). À côté du développement et de la mise en oeuvre de différentes horloges optiques avec des incertitudes fractionnelles estimées d'un ordre de grandeur de 10 −18 , les travaux sous-jacents sur les lasers ultra-stables comme éléments centraux ainsi que les moyens de comparer les horloges optiques lointaines avec des étalons transportables, des fibres optiques ou des rapports de fréquence * 507 sont exposés. Finalement, les conditions, les méthodes et les prochaines étapes sont discutées, qui sont des prérequis à une redéfinition de la seconde.

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Section: Comparisons Of Optical Clocks Remote From Each Othermentioning

confidence: 99%

Section: Comparisons Of Optical Clocks Remote From Each Othermentioning

confidence: 99%

Towards a redefinition of the second based on optical atomic clocks

Riehle

2015

Comptes Rendus. Physique

149

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“…Detailed reviews of these two well-established approaches their variants and state-of-art in year 2002 are given by (Bauch and Telle 2002, pages 828-834) and (Levine 2002) and references therein, in addition to many books. An excellent recent summary of both techniques is provided by (Bauch 2015).…”

Section: Satellite Linksmentioning

confidence: 99%

Atomic clocks for geodesy

et al. 2018

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We review experimental progress on optical atomic clocks and frequency transfer, and consider the prospects of using these technologies for geodetic measurements. Today, optical atomic frequency standards have reached relative frequency inaccuracies below 10, opening new fields of fundamental and applied research. The dependence of atomic frequencies on the gravitational potential makes atomic clocks ideal candidates for the search for deviations in the predictions of Einstein's general relativity, tests of modern unifying theories and the development of new gravity field sensors. In this review, we introduce the concepts of optical atomic clocks and present the status of international clock development and comparison. Besides further improvement in stability and accuracy of today's best clocks, a large effort is put into increasing the reliability and technological readiness for applications outside of specialized laboratories with compact, portable devices. With relative frequency uncertainties of 10, comparisons of optical frequency standards are foreseen to contribute together with satellite and terrestrial data to the precise determination of fundamental height reference systems in geodesy with a resolution at the cm-level. The long-term stability of atomic standards will deliver excellent long-term height references for geodetic measurements and for the modelling and understanding of our Earth.

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“…In these applications, the local optical time scale would be either compared against or synchronized to a distant time scale via terrestrial or satellite free-space links. Existing rf-based techniques can support time transfer over free-space links but are limited to 10-to 100-ps accuracy and ∼1-ps stability, 100 to 1000 times worse than optical oscillators [21][22][23]. The highest performance rf system to date is planned for the ACES mission and will support 300-fs timing stability at 300-s integration and <6-ps timing stability over days from ground to space [24,25].…”

Section: Introductionmentioning

confidence: 99%

Synchronization of Distant Optical Clocks at the Femtosecond Level

et al. 2016

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The use of optical clocks or oscillators in future ultraprecise navigation, gravitational sensing, coherent arrays, and relativity experiments will require time comparison and synchronization over terrestrial or satellite free-space links. Here, we demonstrate full unambiguous synchronization of two optical time scales across a free-space link. The time deviation between synchronized time scales is below 1 fs over durations from 0.1 to 6500 s, despite atmospheric turbulence and kilometer-scale path length variations. Over 2 days, the time wander is 40 fs peak to peak. Our approach relies on the two-way reciprocity of a single-spatial-mode optical link, valid to below 225 attoseconds across a turbulent 4-km path. This femtosecond level of time-frequency transfer should enable optical networks using state-of-the-art optical clocks or oscillators.

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Time and frequency comparisons using radiofrequency signals from satellites

Cited by 24 publications

References 24 publications

Towards a redefinition of the second based on optical atomic clocks

Towards a redefinition of the second based on optical atomic clocks

Atomic clocks for geodesy

Synchronization of Distant Optical Clocks at the Femtosecond Level

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