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

Abstract

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, J 2 , 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, z A , ζ A , and θ A , 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. 352 J. L. HILTON ET AL.Finally, we recommend that the terms precession of the equator and precession of the ecliptic replace the terms lunisolar precession and planetary precession, respectively.

The Geodesist’s Handbook 2016

“…The IERS should take appropriate measures, in conjunction with the IAU Working Group on reference frames, to maintain the ICRF and its ties to the reference frames at other wavelengths. [J. L. Hilton et al 2006], and recommends that the terms lunisolar precession and planetary precession be replaced by precession of the equator and precession of the ecliptic, respectively, and that, beginning on 1 January 2009, the precession component of the IAU 2000A precession-nutation model be replaced by the P03 precession theory [Capitaine et al 2003] in order to be consistent with both dynamical theories and the IAU 2000 nutation. (2006) is a supplement to the IAU 2000 resolutions on reference systems, containing primarily two recommendations, the first to harmonize the name of the pole and origin to "intermediate" and a second recommendation fixing the default orientation of the BCRS and GCRS, which are assumed to be oriented according to the ICRS axes (for more information see the IERS Conventions 2010 [Petit et al 2010]).…”

Data Association Algorithms for Tracking Satellites

“…Effective Jan 1, 2009, the IERS recommends the use of the new International Astronomical Union (IAU) models for nutation and precession to perform this GCRF/ITRF transformation. [3,22,23,24,25,26,27 [3,5,28].…”

The IAU 2009 system of astronomical constants: the report of the IAU working group on numerical standards for Fundamental Astronomy

“…The value is taken from Capitaine et al (2005). A discussion about the uncertainty can be found in Bourda and Capitaine (2004) and in Hilton et al (2006) while a discussion about the components of the J 2 variation can be found in Cheng and Tapley (2004) with a 2008 AGU update (2008AGUFM.G33A0673C).…”

“…Obliquity of the ecliptic at J2000.0, J2000 The obliquity of the ecliptic at J2000.0, J2000 , is from the Hilton et al (2006) report from the IAU Working Group on precession and the ecliptic. This value is taken from the P03 precession model of Capitaine et al (2003) and was adopted in IAU 2006 Resolution B1.…”