Importance of a Common Framework for the Realization of Space-Time Reference Systems

  • Gérard Petit
Conference paper
Part of the International Association of Geodesy Symposia book series (IAG SYMPOSIA, volume 120)


General relativity establishes a distinction between proper quantities which are directly measurable and coordinate quantities which depend on some conventions. While basic mesurements are proper quantities (in nearly all cases either time or frequency is measured), coordinates are the necessary tool with which to study, by modeling, the interactions of physical phenomenon with the measurements. They are also the basic instrument for exchanging and summarizing the results of the measurements, mostly through the coordinates of objects (geodetic station, radio-source…) realizing a space reference.

The paper addresses the issue of how the realization of space-time references may be affected by the choice of coordinate conventions. Some techniques used in space geodesy and astrometry will be studied, stressing how the model chosen, or other assumptions made explicitly or implicitly, influence the results (coordinate quantities). Particular emphasis will be on the issues on time. Indeed the prospects in time metrology are such that new definitions should be drawn to make the best use of the next generation of clocks and be able to compare them. In all fields, however, it is of ever increasing importance for all users to deal with properly defined quantities and common conventions, since the measurement uncertainty in any technique is bound to decrease. For this reason, the Bureau International des Poids et Mesures and the International Astronomical Union have created in 1997 the Joint Committee on relativity for space-time reference systems and metrology, which has among its tasks “to establish definitions and conventions to provide a coherent relativistic frame for all activities in space-time references and metrology at a sufficient level of uncertainty”.


Frequency Standard Space Geodesy International Astronomical Barycentric System Atomic Time Scale 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Aces (1992): Proc. ACES Utilisation Workshop, Busca G. (ed), ESA.Google Scholar
  2. Bjerhammar A. (1985): Bull. Géod. 59, 207.CrossRefGoogle Scholar
  3. Bursa M. (1995): Report of the IAG SC3 Fundamental Constants, XXI IAG General Assembly.Google Scholar
  4. Clairon A. et al. (1995): Preliminary accuracy evaluation of a cesium fountain frequency standard. Proc. Fifth Symp. On Frequency Standards and Metrology, J.C. Bergquist (ed.), World Scientific, 49–59.Google Scholar
  5. Damour T., Soffel M., Xu C. (1991): General relativistic celectial echantcs. 1. Method and definition of reference systems. Phys. Rev. D 43, 3273.Google Scholar
  6. Eubanks T.M.E. (ed.) (1991: Proc. USNO Workshop on relativistic models for use in space geodesy.Google Scholar
  7. Fisk P.T.H., Sellars M.J., Lawn M.A., Coles C. (1995): A microwave frequency standard based on trapped, buffer gas-cooled 171 Yb + ions. Proc. Fifth Symp. on Frequency Standards and Metrology, J.C. Bergquist (ed.), World Scientific, 27–32.Google Scholar
  8. Fukushima T. (1995): Time ephemeris. Astron. Astrophys. 294, 895.Google Scholar
  9. Gontcharov G. (1998): Future galactic dynamical reference frame. Journées 1998 Systèmes de Références spatiotemporels, Obs. de Paris.Google Scholar
  10. Groten, E. (1998): Circular letter 98/1, IAG SC3 Fundamental Constants.Google Scholar
  11. Kopejkin, S.M. (1991): manuscripta geodetica 16, 301.Google Scholar
  12. IAU (1991): IAU Transactions Vol. XXIB, Kluwer pub.Google Scholar
  13. IERS (1992): IERS Standards (1992). IERS TN13, McCarthy D.D. (ed.), Obs. de Paris.Google Scholar
  14. IERS (1996): IERS Conventions (1996). IERS TN21, McCarthy D.D. (ed.), Obs. de Paris.Google Scholar
  15. Klioner S. (1998): Working document JCR03.C.Google Scholar
  16. Mann A.G. et al. (1998): Proc. 1998 IEEE Frequency Control Symposium, p. 13.Google Scholar
  17. Petit G., Tavella P. (1996): Pulsars and time scales. Astron. Astrophys. 308, 290.Google Scholar
  18. Petit G., Wolf P. (1997): Computation of the relativistic rate shift of a frequency standard. IEEE Trans. IM 46, 2 201.Google Scholar
  19. Simon E. et al. (1997): Proc. 11th European Frequency and Time Forum, p. 43.Google Scholar
  20. Soffel et al. (1988): manuscripta geodetica 13, 143.Google Scholar
  21. Tjoelker R.J., Prestage J.D., Maleki L., (1995): Record frequency stability with mercury in a linear ion trap. Proc. Fifth Symp. on Frequency Standards and Metrology, J.C. Bergquist (ed.), World Scientific, 33–38.Google Scholar
  22. Wolf P., Petit G. (1995): Relativistic theory for clock syntonization and the realization of geocentric coordinate times. Astron. Astrophys. 304, 653.Google Scholar
  23. Wolf P., Petit G. (1998): Working document JCR03.a.Google Scholar

Copyright information

© Springer-Verlag Berlin · Heidelberg 2000

Authors and Affiliations

  • Gérard Petit
    • 1
  1. 1.Bureau International des Poids et MesuresSèvres CedexFrance

Personalised recommendations