CoAuthors

Pierre Exertier (CNRS Géoazur, France); Frank G. Lemoine (NASA GSFC, USA); Nikita P. Zelensky (Stinger Ghaffarian Technologies, USA); Douglas S. Chinn (NASA GSFC, USA); Hugues Capdeville (CLS, France)

The Time Transfer by Laser Link (T2L2) experiment on-board the Jason-2 satellite aims to synchronize remote ground clocks which provide Time & Frequency references in Satellite Laser Ranging (SLR) stations. We recently developed a dedicated time transfer method in order to measure the time differences between SLR stations relative to the Grasse Geodetic observatory. It reveals at the measurement level systematic errors in the laser ranging data leading to a desynchronization of the network relative to UTC at the level of several hundreds of nanoseconds to a few microseconds. We show some examples of the time series of time biases for a set of SLR stations and we describe how the time series have been summarized into a unique correction file.

In addition, the T2L2 experiment gave us the opportunity to describe the frequency behavior of the Jason-2 oscillator, by using data from the ground-to-space time transfer passes above some SLR stations. The resulting deterministic model enables to describe the main non linear effects (frequency responses of the oscillator during successive exposures of the satellite above the SAA area, and additionally temperature variations) that affect the on-board oscillator of the Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) system. These are at the level of a few 10^(-12) over tens of minutes, which corresponds to around 0.3-0.4 mm/s and thus have the potentiality to improve both the Precise Orbit Determination process and the computation of station-coordinate solutions.
We present the method that has been established to extract these a priori quantities, and we show how these Doppler corrections affect the Doppler measurements over a set of beacons, namely Toulouse, Kourou, Hartebeesthoek and Terre Adelie.