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IERS Message No. 333                                       July 03, 2017
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Changes in the IERS EOP C01 series


IERS EOP C01 series is the long term combined EOP solution of IERS
starting in 1846 and ending now.

Since 2017 June 25 C01 files have undergone the following changes:

- We provide UT1 - TAI (or UT1 - TE + 32.184 s before 1958) from 1956
instead of UT1 - UTC for two reason: 1) the time scale UTC does not
formally exist before 1961; 2) UT1 - TAI is more appropriate than
discontinuous UT1 - UTC for geophysical studies. Note that
d(UT1-TAI)/dTAI = - Delta (LOD)/LOD,
where LOD = 86400 SI and Delta LOD is the length of day change.

- The format has been upgraded consequently, headers specify the
parameters and unit of the C01 data, given in 6 files depending on
format, reference precession-nutation model, and time span. Details are
given in http://hpiers.obspm.fr/iers/eop/eopc01/EOPC01.GUIDE.

All files can be downloaded from http://hpiers.obspm.fr/iers/eop/eopc01/


Christian Bizouard
IERS EOP Center
Observatoire de Paris / SYRTE
77 av. Denfert-Rochereau
75014 Paris


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