Two-way satellite time and frequency transfer (TWSTFT) is one of the time and frequency transfer methods which contributes to the generation of Coordinated Universal Time. A pair of earth stations transmits and receives CDMA (Code Division Multiple Access) signals through a geostationary communication satellite and is connected to a reference signal.

TWSTFT Modem for Earth Station A

TWSTFT Modem for Earth Station B

Satellite Time and Ranting Equipment (SATRE)

  • 1 – 3 receiver channels
  • Automated measurements
  • Operates unmanned, 24 / 7
  • Remote control over TCP/IP
  • Data transfer via TWSTFT link from remote site
  • Sub-nanosecond precision TWSTFT with real time results
  • Internal measurement database for the last three months on a one minute basis

A TWTFT modem is capable of synchronizing a slave station clock to an accuracy of less than 5 ns with respect to the Master’s reference clock. Moreover, in the absence of the satellite link, once synchronized, the Modem can keep the time accurate to less than one microsecond over the next 24 hours.


  • Synchronization of one station clock to a remote Master station clock at nanosecond accuracy via a satellite link
  • Comparison of a station clock reference to a remote station Clock reference for time keeping purpose

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