Geodetic methods to determine the relativistic redshift at the level of 10 - 18 in the context of international timescales: a review and practical results

verfasst von
Heiner Denker, Ludger Timmen, Christian Voigt, Stefan Weyers, Ekkehard Peik, Helen S. Margolis, Pacôme Delva, Peter Wolf, Gérard Petit
Abstract

The frequency stability and uncertainty of the latest generation of optical atomic clocks is now approaching the one part in 10 18 level. Comparisons between earthbound clocks at rest must account for the relativistic redshift of the clock frequencies, which is proportional to the corresponding gravity (gravitational plus centrifugal) potential difference. For contributions to international timescales, the relativistic redshift correction must be computed with respect to a conventional zero potential value in order to be consistent with the definition of Terrestrial Time. To benefit fully from the uncertainty of the optical clocks, the gravity potential must be determined with an accuracy of about 0.1m2s-2, equivalent to about 0.01 m in height. This contribution focuses on the static part of the gravity field, assuming that temporal variations are accounted for separately by appropriate reductions. Two geodetic approaches are investigated for the derivation of gravity potential values: geometric levelling and the Global Navigation Satellite Systems (GNSS)/geoid approach. Geometric levelling gives potential differences with millimetre uncertainty over shorter distances (several kilometres), but is susceptible to systematic errors at the decimetre level over large distances. The GNSS/geoid approach gives absolute gravity potential values, but with an uncertainty corresponding to about 2 cm in height. For large distances, the GNSS/geoid approach should therefore be better than geometric levelling. This is demonstrated by the results from practical investigations related to three clock sites in Germany and one in France. The estimated uncertainty for the relativistic redshift correction at each site is about 2 × 10 - 18.

Organisationseinheit(en)
Institut für Erdmessung
Externe Organisation(en)
Physikalisch-Technische Bundesanstalt (PTB)
National Physical Laboratory
Observatoire de Paris (OBSPARIS)
Bureau International des Poids et Mesures (BIPM)
Typ
Artikel
Journal
Journal of geodesy
Band
92
Seiten
487-516
Anzahl der Seiten
30
ISSN
0949-7714
Publikationsdatum
05.2018
Publikationsstatus
Veröffentlicht
Peer-reviewed
Ja
ASJC Scopus Sachgebiete
Geophysik, Geochemie und Petrologie, Computer in den Geowissenschaften
Elektronische Version(en)
https://doi.org/10.1007/s00190-017-1075-1 (Zugang: Offen)
 

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