Joint Working Group

JWG 3.1: Consistent improvement of the Earth’s rotation theory (joint with IAU)

Chair: José M. Ferrándiz (University of Alicante, Spain)

Vice-Chair: Cheng-Li Huang (Shanghai Observatory, China)

Tasks are cast into two groups for the clarity’s sake. Members and correspondents must participate in an interactive and coordinated way.

Core of Theory (chaired by Alberto Escapa):

Revision of the reference system and frames used in theoretical developments to ensure they are or can be made consistent with the reference frames used in observation processing, and that all EOP are referred to the same frames;
Extend the basic Earth model to get it closer to state of the art models and relaxing tight hypothesis on structure invariance (e.g., triaxial, updated tidal models for solid earth and oceans, possibility of accounting better for motion components of angular moment, time-varying gravity and realistic J2 variation, possibility of allowing for relative motions of the main layers…);
Update the tidal potential raised by external bodies;
Assess deeply the impact of relativity;
Recompute consistently second order effects and deriving a solution for precession-nutation accurate at the observation (or GGOS) level;
Revisit the problem of separation of nutations and polar motion, in particular at the sub-diurnal level.

Observations (chaired by Maria Karbon):

Ensure that hypothesis, equations and models used in the data analysis packages are consistent with those in theory and compliant with the IAU-IAG-IUGG resolutions;
Providing guidance and help to the potential update and revision of definitions;
Check the new theory and fit it to observations.