Report of the International Astronomical Union Division I Working Group on Precession and the Ecliptic

A Correction to this article is available

This article has been updated


The IAU Working Group on Precession and the Equinox looked at several solutions for replacing the precession part of the IAU 2000A precession–nutation model, which is not consistent with dynamical theory. These comparisons show that the (Capitaine et al., Astron. Astrophys., 412, 2003a) precession theory, P03, is both consistent with dynamical theory and the solution most compatible with the IAU 2000A nutation model. Thus, the working group recommends the adoption of the P03 precession theory for use with the IAU 2000A nutation. The two greatest sources of uncertainty in the precession theory are the rate of change of the Earth’s dynamical flattening, ΔJ2, and the precession rates (i.e. the constants of integration used in deriving the precession). The combined uncertainties limit the accuracy in the precession theory to approximately 2 mas cent−2.

Given that there are difficulties with the traditional angles used to parameterize the precession, zA, ζA, and θA, the working group has decided that the choice of parameters should be left to the user. We provide a consistent set of parameters that may be used with either the traditional rotation matrix, or those rotation matrices described in (Capitaine et al., Astron. Astrophys., 412, 2003a) and (Fukushima Astron. J., 126, 2003).

We recommend that the ecliptic pole be explicitly defined by the mean orbital angular momentum vector of the Earth–Moon barycenter in the Barycentric Celestial Reference System (BCRS), and explicitly state that this definition is being used to avoid confusion with previous definitions of the ecliptic.

Finally, we recommend that the terms precession of the equator and precession of the ecliptic replace the terms lunisolar precession and planetary precession, respectively.

This is a preview of subscription content, access via your institution.

Change history


  1. G. Bourda N. Capitaine (2004) Astron. Astrophys. 428 691 Occurrence Handle10.1051/0004-6361:20041533 Occurrence Handle2004A&A...428..691B

    Article  ADS  Google Scholar 

  2. P. Bretagnon A. Fienga J.-L. Simon (2003) Astron. Astrophys. 400 785 Occurrence Handle10.1051/0004-6361:20021912 Occurrence Handle2003A&A...400..785B

    Article  ADS  Google Scholar 

  3. N. Capitaine P.T. Wallace J. Chapront (2003a) Astron. Astrophys. 412 567 Occurrence Handle10.1051/0004-6361:20031539 Occurrence Handle2003A&A...412..567C

    Article  ADS  Google Scholar 

  4. N. Capitaine J. Chapront S. Lambert P.T. Wallace (2003b) Astron. Astrophys. 400 1145 Occurrence Handle10.1051/0004-6361:20030077 Occurrence Handle2003A&A...400.1145C

    Article  ADS  Google Scholar 

  5. N. Capitaine P.T. Wallace J. Chapront (2004) Astron. Astrophys. 421 365 Occurrence Handle10.1051/0004-6361:20035942 Occurrence Handle2004A&A...421..365C

    Article  ADS  Google Scholar 

  6. N. Capitaine P.T. Wallace J. Chapront (2005) Astron. Astrophys. 432 355 Occurrence Handle10.1051/0004-6361:20041908 Occurrence Handle2005A&A...432..355C

    Article  ADS  Google Scholar 

  7. T. Fukushima (2003) Astron. J. 126 494 Occurrence Handle10.1086/375641 Occurrence Handle2003AJ....126..494F

    Article  ADS  Google Scholar 

  8. W. Harada T. Fukushima (2004) Astron. J. 127 531 Occurrence Handle10.1086/380220 Occurrence Handle2004AJ....127..531H

    Article  ADS  Google Scholar 

  9. Hilton, J. L.: 2006, in preparation.

  10. IAU 2001, “Proceedings of the Twenty-fourth General Assembly, Manchester 2000,” In: H. Rickman, (ed.), Transactions of the International Astronomical Union, Vol. XXIVB, (Astronomical Society of the Pacific 2001, Provo, UT), pp. 43–44.

  11. IERS 2004, “IERS Conventions (2003),” IERS Technical Note 32, In: D.D. McCarthy and G. Petit (eds.), Frankfurt am Main: Verlag des Bundesamts für Kartographie und Geodäsie.

  12. J.H. Lieske T. Lederle W. Fricke B. Morando (1977) Astron. Astrophys. 58 1 Occurrence Handle1977A&A....58....1L

    ADS  Google Scholar 

  13. J.H. Lieske (1979) Astron. Astrophys. 73 282 Occurrence Handle1979A&A....73..282L

    ADS  Google Scholar 

  14. P.M. Mathews T.A. Herring B.A. Buffet (2002) J. Geophys. Res. 107 B4 Occurrence Handle10.1029/2001JB000390

    Article  Google Scholar 

  15. Newcomb, S.: 1894, Astron. Papers Am. Ephemeris, 5, Part 4, 301–378

    Google Scholar 

  16. E.M. Standish SuffixJr. (1981) Astron. Astrophys. 101 L17 Occurrence Handle1981A&A...101L..17S

    ADS  Google Scholar 

  17. Wilkins, G. A.: 1987, IAU Trans., XXB, S1.

  18. J.G. Williams (1994) Astron. J. 108 711 Occurrence Handle10.1086/117108 Occurrence Handle1994AJ....108..711W

    Article  ADS  Google Scholar 

Download references

Author information



Corresponding author

Correspondence to J. L. Hilton.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Hilton, J.L., Capitaine, N., Chapront, J. et al. Report of the International Astronomical Union Division I Working Group on Precession and the Ecliptic. Celestial Mech Dyn Astr 94, 351–367 (2006).

Download citation


  • precession and the ecliptic
  • reference systems