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IERS Message No. 547                                    January 12, 2026
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Fourth update of the 2020 C04 solution


Following a decision taken during the IERS DB No. 81, the pole
coordinates (xp, yp) and their rates (xrt, yrt) will be updated on the
period 1/1/2021 - 31/12/2024 by taking the values corresponding to the
ITRF2020-u2024. 
<https://itrf.ign.fr/ftp/pub/itrf/itrf2020-u2024/
ITRF2020-u2024_EOP-F1.DAT>

This change will eliminate systematic effects coming from the IGS finals
solution, that was not fully recalculated in the ITRF2020 solution over
this period. The name of the updated series will remain unchanged as
well as their path:

https://hpiers.obspm.fr/iers/eop/eopc04

Values for (xp, yp) and (xrt, yrt) sampled at 12h UTC are exactly those
of ITRF2020-u2024, whereas values at 0h result from a spline
interpolation.

The change will be effective from February 5, 2026 (Thursday).

The former solution will be archived in the repository
 
https://hpiers.obspm.fr/iers/eop/eopc04_20_v3

Beyond February 5, 2026 these series will no longer have any future
updates. 

Christian Bizouard
IERS Earth Orientation Centre


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