The Combined Solution C04 for Earth Orientation Parameters Consistent with International Terrestrial Reference Frame 2005

The Earth Orientation Center of the IERS, located at Paris Observatory, SYRTE, has the task to provide to the scientific community the international reference time series for the Earth Orientation Parameters (EOP), referred as ”IERS C04 ” (Combined 04), resulting from a combination of operational EOP series, each of them associated with a given geodetic technique. The procedure developed to derive the C04 solution was recently upgraded back to 1993. The main objective is to insurre its consistency with respect to the newly release ITRF 2008. Due to the separate determination of both terrestrial reference frames and EOP, there has been a slow degradation of the overall consistency since the least ITRF release in 2005, and discrepancies at the level of 50 micoarseconds for x pole coordinate exists between the current IERS C04 and the ITRF realization. We have taken this opportunity to upgrade the numerical combination procedure. Now there are better estimates of the errors of combined values. Individual EOP series have been reprocessed since 1993. Pole coordinates are now fully consistent with ITRF. The new C04 solution, referred as 08 C04, updated two times per week became the official C04 solution since february 2010