A study of ionospheric delay corrections for next-generation two-way satellite time and frequency transfer

Time scale difference has been compared at nanosecond level so far by using two-way satellite time and frequency transfer (TWSTFT), benefiting from many signal delays are pretty canceled out due to the reciprocity of propagation path. For next-generation TWSTFT which compares time scale difference at sub-nanosecond level, further studies for signal delays are necessary. This work studies the impact of the ionospheric delay corrections on next-generation TWSTFT. The results demonstrate that the ionospheric corrections vary with both latitude and solar activity. At low latitudes and during moderate or high solar activity, they can reach 200 picoseconds, and thus can affect the time precision of sub-nanosecond next-generation TWSTFT.