Joint Working Groups

JWG 3.1: Improving Theories and Models of the Earth’s Rotation (joint with IAU)

Chair: Jose Manuel Ferrandiz Leal (University of Alicante, Spain)

Vice-Chair: Richard Gross (Jet Propulsion Laboratory, Pasadena, USA)

Program of Activities :

At short term, intended as two years in this context, the JWG is committed to derive supplementary models for the Celestial Pole Offsets (CPO) evolution, in part of semi-empirical and semi-analytical nature, and able to increase significantly the explained variance of the current theories and models. According to the recommendations of the 2019 GGOS-IERS Unified Analysis Workshop, the priority tasks of building such models will include:  

• updating the amplitudes of the leading nutations of the IAU2000 theory and testing shortened series for certain operational purposes;
• correcting the inconsistencies found in the precession-nutation models;
• test the available FCN models (for explaining CPO variance) and consider whether the IERS should recommend FCN models or not.

The two years term being too short to develop and publish a fully dynamically consistent theoretical approach to support those models, that activity will likely continue till the end of the term. Theoretical developments must also address to advancing in all the aspects made explicit on resolution 5, like using a consistent framework for all the Earth Orientation Parameters, with regard to reference systems and frames, background models, standards, and adaptation of the developments to the current knowledge of the dynamic Earth, from its inner components to its outer layers. The chairing people may assign specific tasks with delimited scopes to volunteer members and correspondents, according to their expertise, availability and initiative.

JWG 3.2: Global combined GNSS velocity field (joint with IAG Commissions 1 and 2)

Chair: Alvaro Santamaría-Gómez (GET, Université de Toulouse, CNES, CNRS, IRD, UPS, Toulouse, France)

Vice-Chair: Roelof Rietbroek (University of Bonn, Germany)

Program of Activities 

• Collect velocity fields from GNSS and other techniques.
• Combine the GNSS velocity fields.
• Assess the differences between the combined GNSS velocity field and other velocity fields.