主要参考说明：
https://hpiers.obspm.fr/iers/eop/eopc04/eopc04.txt
https://hpiers.obspm.fr/iers/eop/eopc04/updateC04.txt
https://celestrak.org/SpaceData/EOP-All.txt
Changes in 20 C04 / Bulletin B---------------- 2023 February 14The 14 C04 ERP solution is replaced by the series 20 C04, consistent with ITRF 2020. Repertory remains the same. The format is changed, pole rates coordinates are included, except for the file eoppc04_IAU2000.62-now. See https://hpiers.obspm.fr/iers/eop/eopc04/eopc04.txt for the description of the new solution. The 14 C04 series will be produced until a non defined date, and put in the neighbouring directory eopc04_14. ------------ 2023 April 8Maria Davis (USNO) noticed that the pole coordinates at 0hUTC were unsually noisy over the period 2021-April 2023. The problem was fixed. ------------- 2023 April 21Until 2023 April 6, extrapolation of the biases of the inter-technique pole coordinate solution entering the C04 over 2019-2021 to the period 2021-2023, and removed accordingly from those series before combination. But, that caused spurious biases with other pole coordinate series, as Maria Davis points out biases, especially in x: +30 µas in the differences USNO Final / JPL - C04. From April 21, intra-technique solutions entering in the C04 over the period 2021-current date are aligned with the IGS repro3 solution recalculated in the ITRF 2020 by Paul Rebishung (IGN).The UT1, celestial pole offsets dX, dY are aligned with ICRF 3, namely the IVS quarterly solution released on 2022 0ctober 31.------------- 2023 April 24From that date we produce of version of the 20 C04 celestial pole offsets dPsi, dEps with respect to IAU 1980 precession-nutation model and named: eopc04.dPsi_dEps.IAU1980.1962-now
C04 2020 solution: 2023, February 14Combined 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 (ms)
- Celestial pole offsets dX, dY or dPsi, dEps (")
- Pole coordinate rates xrt, yrt ("/day)
- Lenght of day offset LOD (ms)2) Download from https://hpiers.obspm.fr/iers/eop/eopc04/4 versions with a new format since 2023, February 14:i) eopc04.1962-now : sampled values at 0hUT / dX, dY IAU 2000 ii) eopc04.dPsi_dEps.1962-now : 0hUT / dPsi, dEps IAU 2000 iii) eopc04.12h.1984-now : 12hUT / dX, dY IAU 2000 iv) eopc04.dPsi_dEps.12h.1984-now : 12hUT / dPsi, dEps IAU 2000 v) eopc04.dPsi_dEps.IAU1980.1962-now: 0hUT / dPsi, dEps IAU 1980The 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) From 1/1/1994 to 31/12/2020 the 12hUT values of the pole coordinates x,y and of their rates xrt and yrt
exactly coincide with the corresponding values obtained for the ITRF 2020 solution. 4) Vondrak combined smoothing: from 1/1/1984 for UT1 and LOD from 1/1/2021 for x,y and ther rates 5) From 1/1/962 to 31/12/1984, ERP values of those of the C0414 solution6) Calibration of the formal uncertainties of the input individual ERP series according to the dispersion with other kindred series 7) Removal of systematic bais / annual terms with respect to ITRF 2020 solution (x, y) and IVS (UT1, dX, dY) 8) Centers contributing to x, y : ITRF 2020 (1994-2021), IGS F (1998-1994, 2021- ), ILRS (2021-), IDS (2021-), IVSR (2021-)
UT1 : IVSF (&984-2020), IVSR (from 2021), IAA Intensive, USNO Intensive, BKG Intensive
dX, dY : IVSF (1984-2020), IVSR (from 2021)
xrt, yrt : ITRF 2020 (1994-2021), IGS F (1998-1994, 2021- )
LOD : IGS F (1998- ), IGS-R (current year), CODE (current year)
EOP: earth orientation parameters
