Earth rotation parameters

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The Earth's rotation  parameters (ERP) are three numerical values ​​that change over time and that describe the state of the Earth's rotation :

The value of DUT1 changes mostly monotonically (always in one direction) and is the cause of the leap seconds by which the Coordinated Universal Time  UTC has to be readjusted every 1 to 3 years of the mean earth rotation. The two pole coordinates vary spirally in the rhythm of the Chandler period (about 430 days, overlaid by a 365 day period), but remain within a 20 meter circle.

The influences of the earth's rotation parameters can be continuously measured on special observatories , the geodetic - astronomical fundamental stations, because all observatories rotate around the earth's axis in 23.9345 hours with the earth's rotation. The measurements are uniformly evaluated by international services. The International Earth Rotation  Service IERS is primarily responsible for this.

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