High Performance Clocks and Gravity Field Determination

Abstract

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${}^{-18}$. 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. 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.

Will be published in Space Science Reviews as special issue on High Performance Clocks which is organized by ISSI

References in corpus (11)

• The IAU 2000 resolutions for astrometry, celestial mechanics and metrology in the relativistic framework: explanatory supplement
• Optical two-way time and frequency transfer over free space
• Relativistic theory for time and frequency transfer to order c^{-3}
• A spaceborne gravity gradiometer concept based on cold atom interferometers for measuring Earth's gravity field
• A coherent optical link through the turbulent atmosphere
• Determination of a high spatial resolution geopotential model using atomic clock comparisons
• Lasers for coherent optical satellite links with large dynamics
• Relativistic Corrections for Time and Frequency Transfer in Optical Fibres
• Post-Newtonian reference-ellipsoid for relativistic geodesy
• Space-time Dynamics Estimation from Space Mission Tracking Data
• Erdmessung mit Quanten und Relativität

Cited by in corpus (19)

• Atomic Clocks for Geodesy
• Point-to-Point Stabilised Optical Frequency Transfer with Active Optics
• Comparing optical oscillators across the air to milliradians in phase and $10^{-17}$ in frequency
• Towards a Transportable Aluminium Ion Quantum Logic Optical Clock
• GENESIS: Co-location of Geodetic Techniques in Space
• The unit of time: present and future directions
• Probing Time Dilation in Coulomb Crystals in a high-precision Ion Trap
• Optical Atomic Clock Comparison through Turbulent Air
• Robust optical clock transitions in trapped ions
• Lunar Time in General Relativity
• The Relativistic Geoid: Gravity Potential and Relativistic Effects
• Potential and scientific requirements of optical clock networks for validating satellite gravity missions
• Normal gravity field in relativistic geodesy
• Cold Atoms in Space: Community Workshop Summary and Proposed Road-Map
• Relativistic theory for time and frequency transfer through flowing media with an application to the atmosphere of Earth
• International Optical Clock Comparison Using the European Optical Fiber Network
• Quantum Physics in Space
• Relativistic geoids and time dependence: quasilocal frames versus isochronometric surfaces
• The QTF-Backbone: Proposal for a Nationwide Optical Fibre Backbone in Germany for Quantum Technology and Time and Frequency Metrology