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In geodesy and astrometry, earth orientation parameters (EOP) describe irregularities in the rotation of planet Earth.EOP provide the rotational transform from the International Terrestrial Reference System (ITRS) to the International Celestial Reference System (ICRS), or vice versa, as a function of time.
The Sub-bureau for Rapid Service and Predictions of Earth Orientation Parameters of the IERS, located at the United States Naval Observatory, monitors the Earth's rotation. Part of its mission involves the determination of a time scale based on the current rate of the rotation of the Earth. Other services of IERS are at the Paris Observatory.
Earth's movement along its nearly circular orbit while it is rotating once around its axis requires that Earth rotate slightly more than once relative to the fixed stars before the mean Sun can pass overhead again, even though it rotates only once (360°) relative to the mean Sun. [n 5] Multiplying the value in rad/s by Earth's equatorial ...
Constructed with input data under the form of time series of station positions and Earth Orientation Parameters. [5] This version introduces extra parameters to describe the year-periodic motion of the stations: A (amplitude) and φ (phase) per-axis. This sort of seasonal variation has an amplitude of around 1 cm and is attributed to non-tidal ...
Models representing the ever-changing orientation of the Earth in space are available from the International Earth Rotation and Reference Systems Service. Examples include: J2000: One commonly used ECI frame is defined with the Earth's Mean Equator and Mean Equinox (MEME) at 12:00 Terrestrial Time on 1 January 2000.
The basic coordinate system is the ITRF reference frame, which is related to the ICRS celestial inertial system by means of very precise Earth Orientation Parameters (EOPs), containing polar coordinates, Earth rotation and nutation parameters. The ITRF data set is revised every 3–5 years, the actual accuracy is in the millimeter area.
Geodesy or geodetics [1] is the science of measuring and representing the geometry, gravity, and spatial orientation of the Earth in temporally varying 3D.It is called planetary geodesy when studying other astronomical bodies, such as planets or circumplanetary systems. [2]
Polar motion of the Earth is the motion of the Earth's rotational axis relative to its crust. [2]: 1 This is measured with respect to a reference frame in which the solid Earth is fixed (a so-called Earth-centered, Earth-fixed or ECEF reference frame). This variation is a few meters on the surface of the Earth.