Observational Validation of Enhanced Earth Rotation Models for the Next IERS Conventions Update

In response to the requirements for GGOS Earth, an international effort is currently underway to revise Earth rotation theory and models involvend in EOP determination to achieve the necessary mas accuracy level. This work, conducted by Joint Working Group IAG 3.1, is divided into a Core of Theory component and an Observations component. While the theoretical team is responsible for developing an extended Earth rotation model through the recomputation of the precession-nutation solution and the refinement of nutation and polar motion separation for enhanced Free Core Nutation (FCN) modeling, this presentation details the outcomes of the observational validation phase. The analysis involves a systematic fit of these emerging models to VLBI data, supported by independent validation using SLR and GNSS orbit determination. This multi-technique approach allows for the quantification of residual signals, the verification of theoretical consistency, and the confirmation that new formulations are correctly implemented within operational analysis software. These validation results serve as a critical contribution to the evaluation and eventual adoption of the revised models for the upcoming IERS Conventions update, guaranteeing that future geodetic standards remain both theoretically robust and empirically sound. We acknowledge the essential contributions of all collaborators involved in this progress.