Evaluation of the secondary representations of the second and their impact on UTC

One-year secondment


The International Bureau of Weights and Measures (BIPM) is an intergovernmental organization whose mandate is to provide the basis for a coherent system of measurements throughout the world, traceable to the International System of Units (SI). The BIPM Headquarters is based in Sèvres, in the outskirts of Paris (France), and has an international staff of about 70. Further information can be found at https://www.bipm.org/en/.

To this aim, the BIPM is seeking a Secondee to support research on the Optimal use of Primary and Secondary Frequency Standards (PSFS) measurements in UTC for the BIPM Time Department:

  • Deadline for applications: 30 September 2023 (23h59 Paris time)
  • Starting date: Early 2024
  • Type of contract: Secondment, one year – Full-time basis


Principal tasks

The joint CCL-CCTF Working Group on Frequency Standards (CCL-CCTF-WGFS) is in charge of the evaluation of the recommended values of standard frequencies for the secondary representations of the second that are regularly updated and published on the BIPM website. The BIPM Time Department is strongly involved in the analysis and further development is needed to finalize the algorithm, the related software and to define the rules for the evaluation of the associated correlations. This work is closely related to the redefinition of the second, one of the main topics of the Consultative Committee for Time and Frequency (CCTF). Part of the work will be devoted to testing the consequences of the work in UTC and in the next evaluation of standard frequencies in preparation for the redefinition of the second.

Additionally, the increasing number of PSFS measurements, submitted by the National Metrology Institutes (NMIs), including direct comparison by optical links, calls for an update of the algorithms of UTC, UTCr, and TT(BIPM).

Main duties and responsibilities

In collaboration with the BIPM Time Department’s physicists, the secondee shall:

  1. Study the current algorithms for the estimation of the standard frequencies for the secondary representation of the second, including the correlation among measurements;
  2. Develop a robust software solution to implement these algorithms, including the estimation of correlations;
  3. Use these tools to test the impact on UTC and on future estimation of the standard frequencies, based on the different scenarios for the redefinition of the second;
  4. Analyze the current algorithm used for the calculation of TT(BIPM) and develop the first updated version, including direct frequency comparison by optical link (constrained solution);
  5. Undertake collaboration with NMIs to get additional data;
  6. Present the obtained results in meetings/conferences and publish in journals.

Qualifications and experience



  • advanced university degree in metrology, physics, mathematics, or a related engineering field.


  • a minimum of 3 year experience in time and frequency metrology
  • experience in developing algorithms and related software
  • good knowledge of statistics and of Python/Matlab coding
  • experience handling any of the above-mentioned tasks and activities, including direct involvement at some level in UTC or PSFS evaluation, is considered an advantage
  • a high-level knowledge of written and spoken English is essential; a working knowledge of French is desirable
  • self-motivation and a willingness to travel
  • ability to maintain good working relations inside and outside the organization.

Background and Employment conditions

The Secondee shall be seconded to the BIPM on a full-time basis in Sèvres in the context of a secondment contract for one (1) year.

The Secondee will remain an employee of the Seconding Party or Releasing Organization (whether an NMI/DI, UTC institute or academic institution). As a result, the Secondee shall continue to receive his/her salary and emoluments as well as respective insurances and allowances, where applicable, from the Seconding Party or Releasing Organization during the secondment period. The Secondee shall not at any time be considered as a staff member of the BIPM.

The BIPM shall pay a monthly subsistence allowance of an amount of EURO 3 000 (three thousand Euro) to the Secondee. No additional allowances, indemnities, insurance coverage or any sums of any kind and no social contributions and advantages shall be paid by the BIPM to the Secondee.

If needed, the BIPM may provide support in facilitating the issuance of visa by the competent authorities and may assist the Secondee in finding local accommodation.


Applications should be sent to the BIPM Time Department Director, Dr Patrizia Tavella, patrizia.tavella(a)bipm.org, by 30 September 2023, 23:59 Paris time. Applications should include a CV, a motivational letter, a letter of support from the Seconding Party or Releasing Organization (for example from the NMI/DI Director) and the names of two referees that can possibly be contacted.

General inquiries about this work opportunity should be addressed to patrizia.tavella(a)bipm.org.

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