After successful completion of the course, students are able to specify the transformation between space fixed and Earth fixed reference systems and the corresponding Earth orientation parameters and to explain the mechanisms and effects associated with the variable rotation of the Earth.

Transformation between celestial and terrestrial reference systems: definition of Earth orientation parameters (EOP), determination of EOP by means of space geodetic techniques; Theoretical background: rotation of a rigid Earth, rotation of a deformable Earth, polar motion, changes of the rotation speed, precession-nutation. Modeling of geophysical effects: angular momentum approach, torque approach, excitation functions.

Explanation of the relevant reference systems, the Earth orientation parameters and the effects and mechanisms affecting Earth rotation with power point slides.

The lecture is given in English at TU Wien and broadcast live with Zoom. The lecturer will provide the recorded presentations via the TUWEL course.

The following topics are discussed in parts during the oral exam:

• Which reference systems are relevant for the treatment of the variable Earth rotation, how are they realized?
• How are changes in the orientation of the Earth described formally?
• How are Earth orientation parameters determined – which techniques deliver which components?
• Which equations are used to describe the rotation of the rigid Earth, which quantities do they contain?
• Why is the rigid Earth's rotation speed constant?
• Which components make up the polar motion of the rigid Earth?
• What is tidal potential? – Where do different frequencies in the spectrum come from, which main periods are present (rough overview)?
• Which axes are considered for the rotation of the rigid Earth and how do they move with respect to the space fixed system?
• How does the body fixed reference system change due to the transition to a deformable Earth, which components are added to the equations of motion?
• Which deformation effects are considered in the solution of the Euler-Liouville equation?
• What is the difference between polar motion of the deformable Earth and polar motion of the rigid Earth?
• What causes variations in the speed of rotation of a deformable Earth model (without atmosphere and oceans)?
• Which effects arise when extending the Earth model for a fluid core?
• Which approaches are used for modelling geophysical effects?
• What is the name of the functions applied for modelling geophysical effects according to the angular momentum approach, into which terms are they split up?
• Variations of length of day / universal time: time scales, periods and causes?
• Phenomena of polar motion: time scales, periods and causes?

Earth Rotation: Theory and Observation (Moritz & Mueller, 1988), The Earth's Variable Rotation: Geophysical causes and consequences (Lambeck, 1980), The Earth and its Rotation (Zharkov et al., 1996), Earth Rotation Variations - Long Period (Gross, 2007)

Lectures of mathematics and physics of the three first semesters required, higher geodesy, Earth gravity field.