Research project MO/33/013 (Research action MO)
Theme: Astronomy – Earth's rotation – Global dynamics of geophysical fluids
Problem:
The planets and moons of our solar system are all animated by a rotational movement about their own axis. If these bodies were spherical, rigid and isolated, their rotation would not fluctuate over time. However, gravitational interaction between close or very massive celestial bodies disturbs their rotation by creating variations in the duration of one revolution (day length) and by modifying the orientation of the axis of rotation relative to the planet's surface (movement of pole) and in space (precession/nutation). Also, the presence on a planet of surface fluid layers (atmosphere, hydrosphere, ocean) and/or an internal fluid layer (liquid core) induces additional variations in rotation. This area of research is currently very important as recognised by the International Earth Rotation Service(IERS) in setting up the geophysical fluids centre in 1998; within this framework, the ORB is in charge of the Special Bureau dedicated to investigating the Core. In the current context of geodetic research, the International Association of Geodesy has launched the Global Geodetic Observation System (GGOS) project, into which this research project integrates naturally.
