E.F. Arias is a member of the International Astronimical Union (IAU) and participates in its working group on the International Celestial Reference System. She is an associate member of the International Earth Rotation and Reference Systems Service (IERS), a member of the International Celestial Reference System Centre, and of the Conventions Centre of the IERS. She is a member of the International VLBI Service (IVS), and of its Analysis Working Group on the International Celestial Reference Frame. She is the BIPM representative to the Governing Board of the International GNSS Service (IGS). She is the BIPM representative to the International Committee for GNSS and she is the chairperson of the Task Force on Time References. She represents the BIPM in the Global Geodetic Observing System (GGOS) Steering Committee, a scientific service of the International Association of Geodesy (IAG). She is a member of the Argentine Council of Research (CONICET) and an associated astronomer at the LNE-SYRTE, Paris Observatory. She is a corresponding member of the Bureau des Longitudes. She is the BIPM representative to the Working Party 7A of the Study Group 7 of the ITU Radiocommunication Sector (ITU-R).

W. Lewandowski is the BIPM representative to the Civil GPS Service Interface Committee (CGSIC) and chairman of its Timing Sub-committee. He is a member of the Scientific Council of the Space Research Centre of the Polish Academy of Sciences. He is also a member of a consultative Group on the Reform of Metrology at the Polish Ministry of Economy, an adviser to a Parliamentary Group on Space, and a member of the Committee on Research on Space Techniques of Polish Academy of Sciences. He is member of European Commission Advisory Group on Galileo Time Infrastructure. Together with E.F. Arias, he is the BIPM representative to the Working Party 7A of the Study Group 7 of the ITU-R, and the UN International Committee on GNSS (ICG).

G. Petit is co-director of the Conventions Centre of the IERS. He is president of the IAU Commission 52 “Relativity in fundamental astronomy”, member of the IAU Working Group on Numerical Standards in Fundamental Astronomy, of the IGS Working Group on Clock Products, of the GNSS Science Advisory Committee of the European Space Agency (ESA), and of the Fundamental Physics Group of the Centre National d'Études Spatiales (CNES).

G. Panfilo collaborates with the Working Group 1 (WG1) on the Expression of uncertainty in Measurement (GUM) of the Joint Committee for Guides in Metrology (JCGM) to provide an example for the new version of the GUM.

E.F. Arias is Executive Secretary of the CCTF and shares with L. Robertsson the Secretariat of CCL/CCTF Frequency Standards Working Group. She is a member of the CCTF WG on Two-Way Satellite Time and Frequency Transfer (TWSTFT), the CCTF WG on Primary Frequency Standards (WGPFS) and the CCTF WG on TAI.

Z. Jiang is a member of the CCTF WG on TWSTFT.

W. Lewandowski is Secretary of the CCTF WG on TWSTFT and Secretary of the CCTF WG on Global Navigation Satellite Systems Time-Transfer Standards (CGGTTS).

G. Panfilo is a member of the CCTF WGPFS and of the Sub-Group on Algorithms of the CCTF WG on TAI and collaborates with the CCTF WGMRA.

G. Petit is a member of the CCTF WG on TAI and its Sub-Group on Algorithms, of the WGPFS, and of the CGGTTS.

L. Robertsson is Executive Secretary of the CCL and a member of the CCL WG on strategic planning and of the Discussion group DG-11 (Lasers). He is the BIPM representative on the Working Group on Gravimetry of the CCM.