{"id":7,"date":"2017-06-12T09:35:12","date_gmt":"2017-06-12T09:35:12","guid":{"rendered":"http:\/\/www.issibern.ch\/teams\/spacetimemetrology\/?page_id=2"},"modified":"2017-06-12T09:35:12","modified_gmt":"2017-06-12T09:35:12","slug":"sample-page","status":"publish","type":"page","link":"https:\/\/www.issibern.ch\/teams\/spacetimemetrology\/","title":{"rendered":"Overview"},"content":{"rendered":"

Research Domains<\/strong><\/span><\/h2>\n
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Fundamental Gravity Theory \u2212 Applied General Relativity \u2212 Relativistic Geodesy \u2212 Relativistic Reference Frames \u2212 Global Gravity Field \u2212 Optical Clocks \u2212 Optical Fibers \u2013 Radio and Laser Links in Space\u2212 Time and Frequency Transfer<\/span><\/p>\n

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Soon after the advent of atomic clocks more than 50 years ago, their unprecedented uncertainties and widespread use required that the definition of time scales and clock comparison procedures be considered rigorously within the theoretical framework of general relativity. Today, the most advanced optical atomic clocks have reached levels of stability and accuracy that significantly surpass the performance of cesium primary standards, for which the best reported results are a stability of 1.4 x 10-14\u00a0 <\/sup>\u03c4-1\/2 <\/sup>where \u03c4\u00a0is the averaging time, and an accuracy of\u00a0 1.1 x 10-16<\/sup> (Heavner et al., 2014). Presently, optical clocks, based on ions or on neutral atoms, exhibit an accuracy of a few parts in 10-18<\/sup> , and neutral lattice clocks achieve a stability down to a few parts in 10-18<\/sup> in a few hours (Schioppo et al. 2017). The workshop team will discuss the reproducibility of optical clocks measurements coming from independent absolute frequency comparisons made in different laboratories, and how to achieve the remote comparison of clocks in consistency with their challenging accuracy level.<\/p>\n

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The team will also review the present procedures and analyze various aspects of the current relativistic modelling to ensure that it is adequate for the need of clocks and time transfer techniques. Accounting for the expected – in near future – improvements in clock and time transfer technology, the team will investigate possible implications in relation to the fundamental physics of relativistic effects influencing time and frequency comparisons between clocks at the10-18<\/sup> level of accuracy, and beyond. The team will also explore how to establish a connection of time metrology to geodetic models of Earth\u2019s gravitational field in order to describe the variation of the clock frequencies due to changes in the gravity potential. High accuracy optical atomic clocks are expected to have a huge impact on the field of Earth science such as geophysics, geodesy, navigation, etc. by using them to measure the gravity potential difference between two, well-defined locations with high temporal (daily) and geospatial resolution at the clock locations. \u00a0This new way to determine the gravity potential will help us to define the geoid (Philipp et al. 2017) and other geodetic parameter needed to describe the gravitational field and other properties of the Earth on a fully relativistic basis, to establish and connect regional and global height systems, to resolve their present discrepancies and to improve gravity field recovery on Earth\u2019s surface and in space. On the long run Relativistic Geodesy will lead to novel services in geodetic and geophysical monitoring.<\/p>\n

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The workshop goal is to establish a tight connection between the theory and practice of precise space geodesy, spacetime metrology, atomic clocks and optical fibers network. This is a rapidly developing new branch of the fundamental physics of time and space with a wide range of applications from geophysics\/geodesy – through realization of the next generation of terrestrial reference frames – to the most fundamental theory of gravity \u2013 general relativity. The workshop continues developments of the topics which were intensively discussed over a week 30 Nov \u2013 4 Dec 2015 at a major ISSI\/HISPAC workshop on \u201cHigh Performance Clocks with Special Emphasis on Geodesy and Geophysics, and Applications to other bodies of the Solar System\u201d (M\u00fcller et al. 2017).<\/p>\n

Project Goals<\/strong><\/span><\/h2>\n