Recommendation 2 of the 18th CCTF (2009)

Characterization of delays of global navigation satellite system (GNSS) equipment in laboratories contributing to International Atomic Time (TAI)

The Consultative Committee for Time and Frequency,

considering that

• the characterization of the delays of time-transfer equipment is essential to ensure the accuracy of the time links for International Atomic Time (TAI);
• uncompensated changes of the hardware delays in a time link may cause significant instability in TAI;
• the Consultative Committee for the Definition of the Second (CCDS) and subsequently the Consultative Committee for Time and Frequency (CCTF) have stressed the importance of calibrating the time-transfer equipment in laboratories contributing data for the calculation of TAI at the BIPM;

aware that

• the Time, Frequency and Gravimetry Section of the BIPM devotes effort to measuring the relative delays of GNSS equipment in laboratories contributing data to the formation of TAI;
• considerable human resources and equipment are necessary to calibrate all the GNSS equipment involved in the formation of the TAI, and to keep these calibrations up to date;

recommends that

• the BIPM continues to organize and run campaigns to measure delays in GNSS equipment in laboratories;
• the principal objective of these campaigns be principally organized to calibrate the equipment in a selected subset of laboratories;
• the Regional Metrology Organizations (RMOs) support the BIPM by organizing campaigns of measurement delays within the frame of regional comparisons to be linked to those conducted by the BIPM;
• the BIPM develop guidelines for this, in consultation with the RMOs.

DOI : 10.59161/CCTF2009REC2E