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IERS Message No. 485                                     August 09, 2023
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Updated ITRF2020 UT1/LOD series


Dear colleagues,

The UT1 and LOD values initially published with ITRF2020 were recently
discovered to be erroneous. The issue could be traced back to a sign
error in the LOD zonal tide corrections applied by the IVS Combination
Center when propagating their ITRF2020 inputs from the middle epochs of
the VLBI sessions to noon. The impact of this error on the UT1 and LOD
values initially published with ITRF2020 was of the order of a few
tenths of milliseconds.

ITRF2020 EOP time series with corrected UT1 and LOD values are now
available at:
* ftp://itrf-ftp.ign.fr/pub/itrf/itrf2020/ITRF2020_EOP-F1.DAT
* ftp://itrf-ftp.ign.fr/pub/itrf/itrf2020/ITRF2020_EOP-F1.DAT
and through the ITRF2020 web page at
https://itrf.ign.fr/en/solutions/ITRF2020.

These files replace the previous erroneous ones. Users who downloaded
either of those two files before 9 August 2023 are advised to download
them again.

As the impact of the error on all other ITRF2020 parameters (pole
coordinates and rates, station coordinates) is completely insignificant,
all other ITRF2020 files have been left unchanged.

Best regards,
Paul Rebischung,
on behalf of the IERS ITRS Center


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