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Earth Orientation Products


We will continue making every reasonable effort to ensure the accuracy and timely publication of our EOP products throughout the current pandemic.

If you have questions or concerns, please contact the EOP C/P Division at: (202 550 6407 or 202 876 6543) or contact the USNO Operations center at: 202 762 0001

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(Please note that several of the links below are broken.  As soon as personnel can remove the broken links, we will do so.)

USNO, as the IERS Rapid Service/Prediction Center, provides daily, weekly, and long-term data products.  Data files and plots are categorized into daily, weekly, and long-term products.  The Bulletin A, updated every Thursday, is available here.  An archive of past issues of Bulletin A is here.  If you would like to receive (or unsubscribe from) the Bulletin A electronically, use the document request form.

Daily Solutions

Daily data files available by anonymous ftp at cddis.  Updated daily

(normally around 17:05 UTC), for highest accuracy real-time applications.

Weekly Solutions

Standard data files available by anonymous ftp at cddis.  Updated weekly

on Thursdays.  Plots of Bulletin A combination and residuals.  Statistical report for contributed series.

Long-term Delta T

Monthly determination of Delta T (TT - UT1) since 1973 and long-term predictions.  Determinations of Delta T are updated approximately quarterly, and long-term predictions from are updated annually.  Data available at cddis.

USNO Master Clock Time
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