Some Operational Aspects of the International Two-Way Satellite Time and Frequency Transfer (TWSTFT) Experiment using INTELSAT Satellites at 307 Degrees East

Eight labondoris are participating in an international TWSTFT experiment. Roguh time and frequency transfers have been performed over a period of almost two pears, including both European and transatlantic time transfers. The performance ofthe regulcv TWSTFT sessions over an esfended period has demonstrated conclusively the usefulness of the TWSTFT method for routine international tinu and frequency comparisons Regular mwsurements are performed three tim per week mulling in a regular but unevenly spaced data set. A mclhod is presented that allows an estimate ofthe values of u,(r) to befonnedfrom these data. In order to maximize eflicient use of paid satellite time an investigation to determine the optimal length of a single TWSTFT session is presenfed. The oplimd experiment length is ddennined by avaluding how long white PM instabilities are the dominant ndsc source during the typical 300-second sampling times currently used. A deiailed investigation ofthefrLqumcy transfers nol*Ld via the transatlantic TWSTFT links UTC(USN0)-UTCfNPL), UTC(USN0)-UTC(PTB), and UTC(PTB)-UTC(NPL) is presented. The investigation focuses on the frquonep instabilities realized, a three-cornered-hat resolution of the u,(r) values, and a cornporison of the transatlantic and inter-European determination of UTC(PTB)-UTC(NPL). Future directions of this TWSTFT experiment arc ourlined