T2L2 - Time transfer by Laser link: a new optical time transfer generation

The T2L2 experiment allows the synchronisation of remote clocks on Earth, and the monitoring of a satellite clock with an accuracy in the 50 ps range. It is based on the propagation of light pulses in space which is better controlled than the radio waves propagation. Some new optical timer and the definition of a new time origin allow direct accurate time transfer without external calibration. The time equations and the uncertainty budget are presented so as to justify the announced performance. This optical time transfer associated to an ultra-stable clock in space has many scientific application as the study of some aspects of the gravitation.