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IERS Message No. 566                                    October 15, 2026
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IERS Rapid Service/Prediction Centre algorithm update


Starting with the weekly Bulletin A products published on 15 October
2026, the daily and weekly products from the IERS Rapid Service/
Prediction Centre will be computed using a new algorithm along with
improved pre-processing of Atmospheric Angular Momentum inputs. The new
algorithm is a Kalman smoother and weighted cubic spline. Going forward,
users should expect to see improvements in the 0-7 day predictions of
UT1-UTC from the current day of computation, with polar motion and
celestial pole offset values remaining mostly unchanged.  After
implementation, slight changes may result if comparing to previous daily
and weekly published values up to one year in the past of the date of
this change.  It is expected that these values are less than 0.05 mas in
polar motion and 20 us in UT1-UTC.

We expect to present more detailed information about the algorithm and
results at upcoming meetings.

The daily and Bulletin A filenames will remain unchanged and continue to
be available at:
https://maia.usno.navy.mil/ser7/

Please report any issues you experience to:
eopcp@us.navy.mil


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