Time and Frequency Transfers to Order 1/c^4
Le Poncin-Lafitte, Ch.
Observatoire de Paris

The current progress in absolute frequency measurements of some optical transitions would provide in a foreseeable future a time-keeping accuracy of the order of 10^(-18) in fractional frequency. Such a level of accuracy will require a fully relativistic modelling of time and frequency transfers up to the order of 1/c^4. A general method enabling to perform the calculations within the post-Newtonian approximation of a large class of metric theories is outlined. The order of magnitude of the main terms is analyzed for a clock onboard a satellite compared with a terrestrial clock.