Earth rotation is an interdisciplinary topic that bridges astronomy and geodesy. Precise knowledge of the Earth's rotation and its variations is needed for positioning and navigating objects on Earth and in space. And the analysis of Earth rotation variations provides important information about interactions between the various components of the Earth system and about global change phenomena.

The objectives of Commission A2 on Rotation of the Earth are to:

1. Encourage and develop cooperation and collaboration in observation and theoretical studies of Earth orientation variations (the motions of the pole in the terrestrial and celestial reference systems and rotation about the pole).
2. Serve the astronomical community by linking it to the official organizations that provide the International Terrestrial and Celestial Reference Systems/Frames (ITRS/ITRF and ICRS/ICRF) and Earth orientation parameters (EOP): International Association of Geodesy (IAG), International Earth Rotation and Reference Systems Service (IERS), International VLBI Service for Geodesy and Astrometry (IVS), International GNSS Service (IGS), International Laser Ranging Service (ILRS), International DORIS Service (IDS).
3. Develop methods for improving the accuracy and understanding of Earth orientation variations and related reference systems/frames.
4. Ensure agreement and continuity of the reference frames used for studying Earth orientation variations with other astronomical reference frames and their densification.
5. Provide means of comparing observational and analysis methods and results to ensure accuracy of data and models and encourage the development of new observation techniques.

The Commission meets its objectives by fostering research and discussion on Earth rotation and reference frames, by organizing topical symposia and workshops, and by forming relevant Working Groups.

• Robert Heinkelmann (IAG Representative)
• Daniela Thaller (IERS Representative)
• Oleg Titov (IVS Representative)