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The Time Transfer by Laser Link experiment (T2L2)

Launched on MeteoSat-P2 in 1992, the "LAser Synchronization from a Stationary Orbit" or LASSO payload validated the concept of optical time transfer by laser link and, more importantly, demonstrated the interest and potential of this high precision method of time transfer. Time transfers were realized between OCA (France) and MacDonald (Texas, USA) stations with a precision better than 100 ps and an accuracy of 1,5 ns.

The T2L2 space payload, initially planned to be onboard MIR in 1999, then with the ACES mission on the ISS, has been accepted in 2005 by the French space agency (CNES) as a passenger of the Jason-2 altimetry satellite. Successfully launched on the 20th of June 2008, the T2L2 instrument was switched on five days after. Once operational, he has began to detect laser pulses from telemetry stations of ILRS network (International Laser Ranging Service).

The Observatoire de la Cote d’Azur (OCA) adapted the technique of satellite laser telemetry (SLR) and lunar laser telemetry (LLR) to the needs of time transfer in order to synchronize remote clocks. Today, the T2L2 instrument has the objective of picosecond stability and sub-nanosecond accuracy.

T2L2 on Jason-2 will allow the precise characterization of the USO (ultra-stable oscillator) used by the DORIS positioning system. Relying on this clock, T2L2 may also permit to perform some orbit restitutions of Jason-2 uniquely by one-way laser ranging. Jason-2 represents an excellent opportunity as its high altitude allows for time transfer with very long integration times in common view mode for most of the continental links.... read more

 MeO Laser Ranging Station at OCA JASON-2 satellite
MeO Laser Ranging Station at OCA JASON-2 satellite