Anybody have more details about this? How it happened or what it might mean for practical timekeeping?
Rob -- -------- Forwarded Message -------- Subject: IERS Message No. 354: Recent changes to the IERS 14 C04 series / Bulletin B Date: Mon, 7 May 2018 10:57:14 +0200 (CEST) From: central_bur...@iers.org To: messa...@iers.org ************************************************************************ IERS Message No. 354 May 07, 2018 ************************************************************************ Recent changes to the IERS 14 C04 series / Bulletin B Dear IERS users, >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, 2018 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, of which the last UT1/CPO determination went back to February 12. So we had to update the C04 series from January 13. With this new solution, the pole coordinates and UT1-UTC were slightly changed. There was 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 was seriously downgraded between IVS dates. Whereas the precision of UT1 intensive is about 30 micros (against 10 micros for R1/R4 UT1), the error introduced by interpolation between two IVS dates is probably much larger. We came to this conclusion, after Frank Reinquin (CNES) put forward an 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. According to the decision of the IERS Directing Board of April 8, 2018 the 14 C04 solution for UT1 was modified on April 16, 2018 by including the contribution of UT1 intensive back to 1996. The old version, updated until 2018/04/16 was put in the directory ftp://hpiers.obspm.fr/iers/eop/eopc04/eopc04.2017/. Kind regards, Christian Bizouard Chair, IERS Earth Orientation Centre ************************************************************************ IERS Messages are edited and distributed by the IERS Central Bureau. If not stated otherwise, the IERS is only the distributor of the message and is not responsible for its content. To submit texts for distribution and to subscribe or unsubscribe, please write to <central_bur...@iers.org>. Archives: http://www.iers.org/Messages/ ************************************************************************
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