The contribution of atomic clocks to the study of spatial-temporal variations of the earth's gravity potential field

Atomic clocks went through tremendous evolutions and ameliorations since their invention in the middle of the twentieth century. The constant amelioration of their accuracy and stability permitted numerous applications in the field of metrology and fundamental physics. For a long time cold atom Caesium fountain clocks remained unchallenged in terms of accuracy and stability. However, this is no longer true with the recent development of optical clocks. This new generation of atomic clock opens new possibilities for applications in chronometric geodesy.

With this progress in clock technology heading towards a relative clock accuracy of 10⁻18, geodetic applications become feasible, such as determining gravity potential differences over large distances at the level of 0.1 m2 s⁻2. In this context, the effect of temporal gravity field variations on the new observable has to be considered. In addition, the clocks could provide results with a high temporal resolution (e.g. 7 to 1 h or less) for understanding the daily to annual evolution of corresponding phenomena, which makes the clocks unique in their ability to continuously monitor regional variations of the gravity potential field, especially when using a well-distributed clock network.

The goal of this paper is firstly to present an extensive review on the contribution of chronometric geodesy to the study of geodynamic phenomena. The second one is to present and analyze the mathematical framework for the estimation of the spatial-temporal variations of the gravity potential field using temporal networks of clocks. The mathematical background of this analysis was inspired from the 4-dimensional integrated geodesy developed in the last decades of the twentieth century.