Dr. Dirk Piester, the time-frequency expert of Physikalisch-Technische Bundesanstalt (PTB) was invited to visit National Time Service Center (NTSC) from January 12 to 15. 

During the visit, Dr. Piester gave us a report titled "PTB time-frequency and the Asia-Pacific cooperation TWSTFT."  In his report, he briefly introduced the present situation of the Two Way Satellite Time and Frequency Transfer (TWSTFT) in Germany, and the progress of the work on TWSTFT between Europe and Asia. Dr. Piester Then visited the time-keeping room and the TWSTFT ground station. Besides, he had a further discussion with the researchers there. 

PTB is a key Computing link in the comparison framework of international automatic time (TAI). The visit of Dr. Piester strengthened the partnership between PTB and NTSC. And it will further promote the development of our time-maintaining and the TWSTFT.