Abstract: The ionosphere errors are corrected in Two-way satellite time and frequency transfer(TWSTFT) using the ionosphere data provided by IGS. The ionosphere total electron content(TEC) is released by IGS at fixed time and geographic grid. The TEC of pierce point at requisite time is calculated by spatial four grids interpolation algorithms and temporal two linear interpolation algorithms. Then it is used to TWSTFT corrected after some processing. The results show that the ionosphere effect on C-band is about (0～0.5)ns range. It is must be considered for time comparison at sub-nanosecond level. The ionosphere product provided by IGS is suit TWSTFT ionosphere correction. It has the advantages of simple method, low cost and high accuracy.

Key words: International GNSS service product, Ionosphere, Two-way time and frequency transfer