################################################################# Combined Earth Rotation Parameter solution consistent with the International Terrestrial Reference Frame (ITRF) 2020 C04 2020 solution Started on 2023, February 14 Last version (v4) started on 2026, February 5 Former versions in repositories <../eopc04_20_v1> <../eopc04_20_v2> <../eopc04_20_v3> See also https://hpiers.obspm.fr/iers/eop/eopc04/updateC04.txt ################################################################# Combined Earth Rotation Parameter solution consistent with the International Terrestrial Reference Frame (ITRF) 2020 Features: 1) Contain daily values of 8 Earth Rotation parameters with their formal errors: - Pole coordinates x, y (") - UT1 - UTC (s) - Celestial pole offsets dX, dY or dPsi, dEps (") - Pole coordinate rates xrt, yrt ("/day) - Lenght of day offset LOD (s) 2) Download from https://hpiers.obspm.fr/iers/eop/eopc04/ 5 options with a new format since 2023, February 14: i) eopc04.1962-now : sampled values at 0hUT / dX, dY IAU 2006/2000A ii) eopc04.dPsi_dEps.1962-now : 0hUT / dPsi, dEps IAU 2006/2000A iii) eopc04.12h.1984-now : 12hUT / dX, dY IAU 2006/2000A iv) eopc04.dPsi_dEps.12h.1984-now : 12hUT / dPsi, dEps IAU 2006/2000A v) eopc04.dPsi_dEps.IAU1980.1962-now : 0hUT / dPsi, dEps IAU 1980 The former format with the file "eopc04_IAU2000.62-now" is maintained (without xrt and yrt parameters) : vi) eopc04_IAU2000.62-now : 0hUT / dX, dY IAU 2000 3) Alignement with ITRF and corresponding updates - From 1/1/1962 to 31/12/1984, ERP values of those of the C0414 solution consistent with ITRF 2014 - From 1/1/1994 to 31/12/2020 the 12hUT values of the pole coordinates x,y and of their rates xrt and yrt are taken equal to the values obtained for the ITRF 2020 solution. - From 1/1/2021 to 31/12/2024 x,y, xrt, yrt are taken (12h values) or interpolated (0h values) from the ITRF2020-u2024 solution (https://itrf.ign.fr/ftp/pub/itrf/itrf2020-u2024/ITRF2020-u2024_EOP-F1.DAT). Update effective on February 5, 2026. Former solution was put in repository ../eopc04_20_v3. - From 25/2/2024, x,y, xrt, xyrt are derived by a weighted combination of IVS Quaterly/Rapid, IGS Final/Rapid, ILRS series 4) Vondrak combined smoothing: from 1/1/1984 for UT1 and LOD from 25/2/2024 for x,y and ther rates 5) Calibration of the formal uncertainties of the input individual ERP series according to the dispersion with other kindred series 6) Removal of systematic bais / annual terms with respect to ITRF 2020 solution prolongated until the current year (x,y) and IVS Final (UT1, dX, dY) 7) Centers contributing to the final C04 solution (stopping 30 days before the current date): x, y : ITRF 2020 + extension (1994-2024), IGS F (2024-from 1 to 3 months before the current date), ILRS (2024-), IDS (1994-2025), IVSR (up to the last 3 months) UT1 : IVSF-quaterly (1984-from 1 to 3 months before the current date), IVSR (up to the last 3 months), IAA Intensive, USNO Intensive, BKG Intensive dX, dY : IVSF-quaterly (1984-up to 3 months before the current date), IVSR (up to the last 3 months) xrt, yrt : ITRF 2020 + extension (1994-2024), IGS F quaterly (2024-from 1 to 3 months before the current date), IGS R (up to the last 3 months) LOD : IGS F (1998-), IGS-R (up to the last 3 months) Combined series since 2025/1/1 #============================================================================ # TECHNIQUE : CENTER #============================================================================ 1rd line ; EOP selection and rescaling error : 0 for no EOP / selection for a non zero value 0 giving the factor to be applied to formal error 2nd : reference epoch (MJD) for the annual term : A cos(arg) + B sin(arg) with arg = 2 pi/365.2 d * (MJD - MJD0) 3rd : x bias A B unit : micro-arc-second 4th : y bias A B micro-arc-second 5th : UT1 bias A B micros 6th : dX bias A B micro-arc-second 7th : dY bias A B micro-arc-second 8th : xrt bias A B micro-arc-second 9th : yrt bias A B micro-arc-second 10th : LOD bias A B micros #============================================================================ # VLBI : IVS-R #============================================================================ x y UT1 dX dY xrt yrt LOD 3.01 1.99 2.87 1.98 1.95 0.00 0.00 1.09 60676.0000 -19.800 -20.6000 -19.6000 12.800 -82.2000 -0.9000 2.800 1.8000 -2.0000 -1.500 8.9000 -4.4000 3.200 4.5000 -12.5000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.100 1.1000 1.7000 #============================================================================ # VLBI : IVS-F #============================================================================ 7.59 7.78 10.51 4.19 4.01 0.00 0.00 2.33 60661.2000 0.400 -1.8000 28.0000 -11.300 -22.4000 -34.6000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 #============================================================================ # VLBI - BKG #============================================================================ 0.00 0.00 2.00 1.48 1.39 0.00 0.00 0.61 60676.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 4.100 0.5000 -0.6000 55.600 -0.4000 -13.5000 35.200 -8.7000 -12.8000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.100 0.4000 -1.2000 #============================================================================ # VLBI : USNO #============================================================================ 0.00 0.00 0.00 0.70 0.60 0.00 0.00 0.18 60676.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 10.200 -8.2000 9.1000 -14.600 4.5000 0.5000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 1.100 -2.6000 -1.8000 #============================================================================ # VLBI Intensive : BKG I #============================================================================ 0.00 0.00 4.75 0.00 0.00 0.00 0.00 0.00 60676.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 -2.000 -8.7000 5.7000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 #============================================================================ # VLBI Intensive : IAA I #============================================================================ 0.00 0.00 2.03 0.00 0.00 0.00 0.00 0.00 60676.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 5.900 -18.3000 2.8000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 #============================================================================ # VLBI Intensive : IAAR I #============================================================================ 0.00 0.00 1.23 0.00 0.00 0.00 0.00 0.00 60676.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 -56.800 -9.9000 -10.7000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 #============================================================================ # VLBI Intensive : USNO I #============================================================================ 0.00 0.00 1.86 0.00 0.00 0.00 0.00 0.00 60676.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 14.400 -4.2000 0.5000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 #============================================================================ # GNSS : IGS-R #============================================================================ 2.59 2.07 0.00 0.00 0.00 2.48 2.63 3.70 60676.0000 -1.200 8.3000 10.3000 -1.800 -9.5000 -1.1000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 -25.000 12.6000 8.1000 -2.000 -0.5000 20.9000 1.000 -2.5000 3.4000 #============================================================================ # GNSS : IGS-F #============================================================================ 3.56 2.76 0.00 0.00 0.00 3.04 3.02 5.29 60676.0000 -10.900 9.1000 6.4000 -6.700 -10.7000 -6.6000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 -9.800 -0.7000 10.7000 -1.700 5.9000 5.5000 0.300 -1.9000 2.6000 #============================================================================ # SLR : ILRS #============================================================================ 5.19 5.38 0.00 0.00 0.00 0.00 0.00 10.03 60676.0000 75.300 51.1000 -54.9000 63.300 -25.3000 32.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 0.000 0.0000 0.0000 5.300 -6.5000 1.7000