The IAU 2006 precession quantities with an improved Earth’s J2 long-term variation

In 2006, the IAU adopted a standard precession theory, the IAU2006 model, in which the time variation of the Earth's dynamical flattening J₂ has an important contribution to the precession rate in longitude. However, a linear J₂ trend, which was valid at that time, is no longer a good approximation and may limit the accuracy of the theory. In this work, we use the most recent satellite laser ranging (SLR) data to model the Earth's J₂ long-term variation with a parabola. It was then implemented in calculating the polynomial expressions for precession quantities with a method similar to the IAU2006 approach.

 

The new precession solution, named IAU2006_J2, is checked against high accurate VLBI data over 45 years. It is clearly more consistent with observations: the overall difference between the observed and modeled positions decreases by about 20%, and most of the curvature signals in the CPO series are reduced. Besides the basic precession parameters, the full set of precession-nutation quantities (X, Y, s, EO ...) compatible with the IAU2006_J2 model are developed, for both classical and CIO-based transformation from the GCRS to the ITRS. Considering its significant improvement, we propose that the IAU2006_J2 precession model be considered in the update of the IERS Conventions which is currently in progress.