This working group was created by the CCTF in 2005. The membership includes 20 individuals from 13 metrology organizations, including the Time, Frequency and Gravimetry Section of the BIPM. The current Chairman is Tom Parker from the National Institute of Standards and Technology (NIST) in Boulder, USA.

Terms of reference

The objectives of this working group as stated in the terms of reference are:

1. Develop and propose standards for the documentation of frequency biases and uncertainties, operational details, and frequency transfer uncertainties for a PFS. Develop and propose standards for the reporting of the results of a PFS evaluation to the BIPM.



2. Provide a forum to evaluate and discuss the consistency among primary frequency standards.



3. Provide a forum to discuss and assess the overall knowledge of the accuracy of the SI second for use in establishing the frequencies of secondary standards (microwave and optical) and possibly an eventual redefinition of the second.



4. Interact with the BIPM on issues related to PFS contributions to the accuracy of TAI, particularly in the process of integration of the first reports of a standard.



5. Encourage and facilitate direct comparisons between primary frequency standards.



6. Encourage and support laboratories with new standards under construction.