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Recommendation 4 of the 17th CCTF (2006)

Concerning the use of Global Navigation Satellite System (GNSS) carrier phase techniques for time and frequency transfer in International Atomic Time (TAI)

The Consultative Committee for Time and Frequency (CCTF),

realizing that

  • atomic frequency standards have achieved unprecedented precision and accuracy, and that further rapid advances in this field are underway,
  • the ability to compare these standards for the realization of International Atomic Time (TAI) is already limited by the accuracy and precision of current time transfer systems;

understanding the complementary nature of different time and frequency transfer techniques, and of different available manifestations of each technique;

noting that

  • GNSS carrier phase techniques have been developed, which are used to routinely generate time and frequency transfer with a sub-daily precision unattained by any other long-distance technology,
  • the costs associated with equipment acquisition, installation, operation, and maintenance are less than the purchase price of a single cesium frequency standard,
  • several institutions have manifested their willingness to reduce the data,
  • many promising software algorithms are either available or under active development;

and considering that instabilities of existing time transfer equipment remain a matter of concern at the nanosecond level;

recommends that

  • the laboratories participating in TAI consider acquiring state-of-the-art geodetic GNSS time receivers,
  • the several institutions currently generating routine solutions institute policies to reduce data from every timing laboratory that is willing to participate and can meet the documentation requirements,
  • the International Bureau of Weights and Measures (BIPM), in a highly cooperative manner, generate its own solutions, make them freely available to others, and add them to its time transfer comparison database,
  • the BIPM begin preparing software and techniques for introduction of the data into the computation of Circular T,
  • the BIPM institute the operational collection of calibration information from the geodetic receivers of participating laboratories, and
  • that the International Committee for Weights and Measures provide the required resources to the BIPM to carry out these recommendations.

The reader should note that the official version of this Resolution is the French text