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 contact us to report any issues you experience.