Analysis of Two-Way Satellite Time and Frequency Transfer with C-Band

Two-Way Satellite Time and Frequency Transfer (TWSTFT) with C-band is influenced more seriously by ionosphere delay than that with Ku-band. The TWSTFT link between Xi'an and Urumchi with C-band has been established and it works via SINOSAT-1 geostationary satellite at 110.5° E with the uplink frequency 6.3 GHz and downlink frequency 4.1 GHz. To study and evaluate the instability introduced by ionosphere delay in the TWSTFT link with C-band, we calculated the influence of ionosphere delay based on global TEC map in 2006 provided by the International GNSS Services (IGS). First, we build a sphere harmonious model based on IGS TEC data file, so that we can easily obtain the TEC at any penetration point on the sphere 450 km above the earth surface at any time. Then, we calculate the two penetration point positions with the coordinates of two stations and the nominal coordinate of the satellite. After that, the uplink and downlink ionosphere delay of each station are calculated, and the influence to TWSTFT is also obtained. The result shows that the non-reciprocity introduced by ionosphere delay in the TWSTFT link with C-band varies day by day, and the maximum amplitude of the daily variation is 0.38 ns in 2006.