Modelling and prediction of the FCN
Abstract
In this paper we investigated the Free Core Nutation (FCN) which is the most significant oscillation in the celestial pole offset residuals with respect to the current IAU 2000 precession-nutation model. A wavelet phase spectrum analysis of the IERS C04 (IAU 2000) data was performed in order to determine areas of stable phase, which would be seen as times of constant period of the FCN. The results show that the retrograde period of the FCN appears to be a function of time, apparently changing between 410 and 490 days. These ''changes" are correlated with Niño 4 data as well as with C20 coefficients of the gravity field. The wavelet modulus for the FCN period is correlated with negative change of the pressure term of the Atmospheric Angular Momentum excitation function. In order to fit the data, a combination of complex least-squares solutions was used to model and predict the FCN oscillation.
- Publication:
-
Journées 2005 - systèmes de référence spatio-temporels
- Pub Date:
- October 2006
- Bibcode:
- 2006jsrs.conf..181K
- Keywords:
-
- Earth rotation;
- reference systems;
- relativity;
- time;
- ephemerides