Achievements, needs and prospects of updating the standards, theories and models of the Earth's rotation

• Autores: Ferrándiz, J. M.; Escapa, A.; Karbon, M.; Belda, S.; Baenas, T.; Huang, C. L.; Liu, J. C.
• Año de publicación: 2025
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Ciencias Astronómicas; Precession and nutation theory; Earth rotation models; Celestial pole offsets (CPO)
• Institución: Universidad Nacional de La Plata

Over the last decade, the IAU and the International Association of Geodesy (IAG) have organised successive Joint Working Groups (JWGs) to improve the theories and models of the Earth's rotation. Their reports revealed inconsistencies and obsolescence of the standard theories and models, and some of underlying concepts, and led to the 2019 IAG and 2021 IAU Resolutions encouraging their improvement in terms of accuracy, consistency, and better adaptation to present knowledge of the actual Earth. The current IAU/IAG JWG on Consistent Improvement of Earth's Rotation Theory (CIERT) is addressing this problem with a particular focus on the theories of precession and nutation (PN). Improving consistency requires that all components of theories and analyses of observational data refer to and use identical reference frames, basic and ancillary Earth models and parameters. In contrast, these in the official PN theories are over 20 years old and do not meet the current standards. Worse, the three main components of these theories are inconsistent with each other regarding underlying geophysical models, free Earth oscillation modes, and some fundamental parameters: e.g. the dynamical ellipticity in IAU2006 is a linear function of time, while in IAU2000 it is a constant whose value needs updating; moreover, the planetary nutations are still a rigid-Earth solution, unlike the lunisolar ones. This presentation reports on the main achievements of several JWG members and their advantages and limitations, focusing on those more consistent and capable of drastically reducing the unexplained variance of the determined celestial pole offsets in the short term.
Facultad de Ciencias Astronómicas y Geofísicas