Calibration of system delays in the European Laser Timing to 10 ps accuracy

Recently the European Laser Timing experiment is under construction. It is an optical link prepared in the frame of the European Space Agency mission Atomic Clock Ensemble in Space. The objective of this laser time transfer is the synchronization of the ground based clocks and the clock on board the International Space Station with precision of the order of units of picoseconds and the accuracy of 50 ps. We are reporting on a progress and results in calibration of the system delays involved.