Changes in 14 C04 / Bulletin B
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2018 March 3
From its production in February 2017, 14 C04 nutation was only based upon the IVS combined solution according to a
recommendation issued by representatives of IVS and IERS. But, on March 3, it turned out that IVS combined solution
had not been updated since January 13, when Bulletin B was made. So, celestial pole offsets (CPO) were set to zero
after this date.
In order to fix this problem, on March 3 we run again the C04 combination by taking all VLBI solutions, which the
last UT1/CPO determination went back to February 12. So we had to update the C04 from January 13. With this new
solution, the pole coordinates and UT1-UTC were slightly changed.
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2018 January
There is a also a serious flaw in UT1 values till January 2018, where UT1 intensive values are no more accounted
after we wrongly follow an advise of an IVS/IERS representative. Because of the error interpolation, UT1 solution is
seriously downgraded between IVS dates. Whereas precision of UT1 intensive is about 30 micros (against 10 micros for
R1/R4 UT1), error introduced by interpolation between two IVS dates is probably much larger. We came to this
conclusion, after Frank Reinquin (CNES) put forward anomalous increase of SLR LAGEOS 1/2 orbital residuals using the
14 C04. Then we discovered that these anomalies were precisely located at the dates where UT1 intensive had been
ignored, and replaced by a pure interpolated values between neighbouring R1/R4 sessions.
Status: wait for IERS DB of April 2018 before to update the whole set of UT1 values since 1996, accounting for UT1
intensives.
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2017 June 7
A 14 C04 version is now sampled at 12hUTC since 1984 (with CPO dX,dY referred to IERS conventional precession-nutation model). With this version IGS pole coordinates are no more inteprolated.
http://hpiers.obspm.fr/iers/eop/eopc04/eopc04.dX_dY.12h.84-now