Improvement Of Comparisons Between T2l2 & Rf Links

The Time Transfer by Laser Link (T2L2) experiment, developed by both CNES and OCA, performs ground to ground time transfer over intercontinental distances. The principle is derived from laser telemetry technology with dedicated space equipment designed to record arrival time of laser pulses at the satellite. Using laser pulses instead of radio frequency signals, T2L2 permits to realize some links between distant clocks with time stability of a few picoseconds and accuracy better than 100 ps.The T2L2 space instrument on board the satellite Jason 2 is in operation since June 2008. Several campaigns were done to estimate both the ultimate time accuracy and time stability capabilities. A first comparison between T2L2 and RF links was performed in 2010 from a campaign between the Observatoire de Paris and the Observatoire de la Cote d'Azur. This campaign required the installation of a transportable laser station in Paris and a first calibration of the links between the laser stations in Paris and Grasse and the local time references. It has demonstrated a phase difference between T2L2 and GPS Carrier Phase or TWSTFT lower than 2 ns rms during 2 months.Since that campaign, T2L2 data processing has been widely improved. This will permit to envision a most extensive comparison between laser and RF techniques. This paper will present some new results of these comparisons in a common view configuration.