Progress in accurate frequency transfer by GPS and GEO carrier phase at CNES

This paper presents the recent improvements in accurate frequency transfer by GPS and GEO (SBAS) carrier phase at CNES. In a previous paper we described the software used at CNES for GPS frequency transfer using carrier phase and we reviewed the performances obtained with two different clock resolution algorithms. In the best case, we obtained a stability of σ_y(τ)=4.10^-15 for τ=10⁴ s between ALGO and NRC1, both stations being driven by a hydrogen maser. In this paper, we present the improvements performed on this software to process GEO measurements. The GEO satellites provide some advantages and drawbacks that are discussed. For the time being, in our configuration, the GEO carrier phase frequency transfer is limited by code noise and ionosphere correction.