10:45 〜 11:00
[G04-2-02] Corrections to IAU2000 nutation series for consistency with IAU2006 precession
A central issue in modern nutation and precession theories is to guarantee consistency among their different parts. This fact is motivated because IAU standards considered in the last decades tackle precession and nutation as separated models that are interconnected, but just partially. However, current accuracies in the determination of the EOPs require, at least, adopting some corrections aimed at suppressing the inconsistencies that have been found between IAU2000 nutation and IAU2006 precession. In fact, IERS Conventions (2010) already includes some corrections to amend the IAU2000 nutation series, but they only cover a small part of the inconsistencies discovered so far.
We will present various corrections that must be accounted for to ensure full consistency and discuss their sources. They can be separated into two groups. The first one is due to the changes of the value of the dynamical ellipticity of the Earth, resulting from components of the precession theory not considered or modeled with insufficient accuracy. These changes induce indirect variations of the nutation amplitudes. In addition the change of ellipticity has a part related with the redistribution of mass within the Earth of tidal and centrifugal nature.
The second group stems from some differences assumed for the Earth model in IAU2006 precession with respect to IAU2000 nutation. The main one was the consideration of a constant J2 rate acting on the precession motion. Its incorporation to the nutation model introduces some out–of–phase and mixed secular nutations. Besides, it is also necessary to consider other effects like those related to the changes in some precession quantities, the time–dependent part of the orbital coefficients, etc.
These corrections should be considered in the updating of the IAU/IAG models of the Earth Rotation or incorporated in the most important standards like IERS Conventions to prevent the appearance of systematics associated to these inconsistencies.
We will present various corrections that must be accounted for to ensure full consistency and discuss their sources. They can be separated into two groups. The first one is due to the changes of the value of the dynamical ellipticity of the Earth, resulting from components of the precession theory not considered or modeled with insufficient accuracy. These changes induce indirect variations of the nutation amplitudes. In addition the change of ellipticity has a part related with the redistribution of mass within the Earth of tidal and centrifugal nature.
The second group stems from some differences assumed for the Earth model in IAU2006 precession with respect to IAU2000 nutation. The main one was the consideration of a constant J2 rate acting on the precession motion. Its incorporation to the nutation model introduces some out–of–phase and mixed secular nutations. Besides, it is also necessary to consider other effects like those related to the changes in some precession quantities, the time–dependent part of the orbital coefficients, etc.
These corrections should be considered in the updating of the IAU/IAG models of the Earth Rotation or incorporated in the most important standards like IERS Conventions to prevent the appearance of systematics associated to these inconsistencies.