What is Earth Orientation?
The term "Earth orientation" refers to the direction in space
of axes which have been defined on the Earth. It is usually measured
using five quantities: two angles which identify the direction of the
Earth's rotation axis within the Earth (polar motion), an angle describing the rotational
motion of the Earth (UT1-UTC), and two angles which characterize the direction of
the Earth's rotation axis in space (celestial pole). With these coordinates, the
orientation of the Earth in space is fully described. The
Rapid Service/Prediction Center
of the International Earth Rotation and Reference Systems Service (IERS) monitors the Earth's orientation and disseminates this information to
many organizations on a continuous basis.
