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High performance clocks and gravity field determination / Jurgen Müller in Space Science Reviews, vol 214 n° 1 (February 2018)  

Public [article]  inSpace Science Reviews > vol 214 n° 1 (February 2018) Titre : High performance clocks and gravity field determination Type de document : Article/Communication Auteurs : Jurgen Müller, Auteur ; D. Dirkx, Auteur ; S. M. Kopeikin, Auteur ; Guillaume Lion , Auteur ; Isabelle Panet , Auteur ; Gérard Petit, Auteur ; Pieter N.A.M. Visser, Auteur Année de publication : 2018 Projets : 3-projet - voir note / , AdOC / Note générale : bibliographie Jürgen Müller gratefully acknowledges support by the DFG Sonderforschungsbereich (SFB 1128: geo-Q) Relativistic Geodesy and Gravimetry with Quantum Sensors. Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] chronométrie [Termes IGN] échelle de temps [Termes IGN] gravimétrie spatiale [Termes IGN] horloge atomique [Termes IGN] International Terrestrial Reference Frame [Termes IGN] potentiel de pesanteur terrestre [Termes IGN] relativité générale Résumé : (auteur) Time measured by an ideal clock crucially depends on the gravitational potential and velocity of the clock according to general relativity. Technological advances in manufacturing high-precision atomic clocks have rapidly improved their accuracy and stability over the last decade that approached the level of 10−18. This notable achievement along with the direct sensitivity of clocks to the strength of the gravitational field make them practically important for various geodetic applications that are addressed in the present paper. Based on a fully relativistic description of the background gravitational physics, we discuss the impact of those highly-precise clocks on the realization of reference frames and time scales used in geodesy. We discuss the current definitions of basic geodetic concepts and come to the conclusion that the advances in clocks and other metrological technologies will soon require the re-definition of time scales or, at least, clarification to ensure their continuity and consistent use in practice. The relative frequency shift between two clocks is directly related to the difference in the values of the gravity potential at the points of clock’s localization. According to general relativity the relative accuracy of clocks in 10−18 is equivalent to measuring the gravitational red shift effect between two clocks with the height difference amounting to 1 cm. This makes the clocks an indispensable tool in high-precision geodesy in addition to laser ranging and space geodetic techniques. We show how clock measurements can provide geopotential numbers for the realization of gravity-field-related height systems and can resolve discrepancies in classically-determined height systems as well as between national height systems. Another application of clocks is the direct use of observed potential differences for the improved recovery of regional gravity field solutions. Finally, clock measurements for space-borne gravimetry are analyzed along with closely-related deficiencies of this method like an extra-ordinary knowledge of the spacecraft velocity, etc. For all these applications besides the near-future prospects, we also discuss the challenges that are related to using those novel clock data in geodesy. Numéro de notice : A2018-197 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s11214-017-0431-z Date de publication en ligne : 30/11/2017 En ligne : https://doi.org/10.1007/s11214-017-0431-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=89864 [article]

The Fresnel–Fizeau effect and the atmospheric time delay in geodetic VLBI / S. M. Kopeikin in Journal of geodesy, vol 89 n° 8 (August 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 8 (August 2015) . - pp 829 - 834 Titre : The Fresnel–Fizeau effect and the atmospheric time delay in geodetic VLBI Type de document : Article/Communication Auteurs : S. M. Kopeikin, Auteur ; B. Han, Auteur Année de publication : 2015 Article en page(s) : pp 829 - 834 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement du signal [Termes IGN] correction atmosphérique [Termes IGN] données ITGB [Termes IGN] interférométrie à très grande base [Termes IGN] International Earth Rotation Service [Termes IGN] rayonnement électromagnétique [Termes IGN] retard troposphérique Résumé : (auteur) The Fresnel–Fizeau effect is a special relativistic effect that makes the speed of light dependent on the velocity of a transparent, moving medium. We present a theoretical formalism for discussing propagation of electromagnetic signals through the moving Earth atmosphere taking into account the Fresnel–Fizeau effect. It provides the rigorous relativistic derivation of the atmospheric time delay equation in the consensus model of geodetic VLBI observations which has never been published before. The paper confirms the atmospheric time delay of the consensus VLBI model used in IERS standards and provides a firm theoretical basis for calculation of even more subtle relativistic corrections. Numéro de notice : A2015-378 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0812-6 Date de publication en ligne : 24/04/2015 En ligne : https://doi.org/10.1007/s00190-015-0812-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76856 [article]