C04 2020 solution: 2023, February 14
Modfified on 2023, July 20

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 (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 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) 

- From 1/1/1962 to 31/12/1984, ERP values of those of the C0414 solution

- 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, 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 1/1/2021 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 

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-current year), 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)