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IERS Message No. 478                                       June 15, 2023
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Updated Alignment Date of the IERS Bulletin A to IERS EOP 20 C04 series


As of Bulletin A Vol XXXVI, No. 026, on 29 June 2023, the IERS Rapid
Service/Prediction Centre will transition the EOP solution to be
consistent with the 20 C04 for polar motion, UT1-UTC, and celestial pole
offsets. This change will result in a difference of less than a RMS of
0.015 mas in polar motion and 15 us in UT1-UTC since MJD 59214 (the end
of ITRF2020). The only users who need to be concerned with this change
are those who need EOP accuracy to be better than 0.1 mas (~0.3 cm at
the Earth's surface, ~1.2 cm at GPS orbit.)

A notice of the change will be contained near the top of the IERS
Bulletin A Vol XXXVI, No. 026, on 29 June 2023, where notes to users are
placed. Users are strongly encouraged to review this message to confirm
the change or to note if the change was not implemented due to technical
issues.

Nick Stamatakos,
IERS Rapid Service / Prediction Centre:
Primary scientist and representative to the IERS Directing Board

Sharyl Byram,
IERS Rapid Service / Prediction Centre:
Production director and lead project scientist


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