Determination of differential delays of earth stations in Paris and Torino from the calibrated OP-IT TWSTFT link

INRiM (Torino) and LNE-SYRTE (Paris) operate two earth stations from which a calibrated two-way link, at the nanosecond level, is established and regularly works in the context of contributions to ongoing activities (TAI of the BIPM) or specific activities (Galileo). Torino and Paris also use two additional earth stations that can be used for specific scientific applications or for redundancy to regular scientific operations. This paper describes the determination of the relative differential delays of the additional stations, from the reference calibrated link, with a combined uncertainty of 1 ns and highlights a bias around 370 ps on the reference calibrated link that may be caused by interference problems between codes at 1 MChip/s within the TWSTFT network.