matrice

Compute the Earth rotation matrix / quaternion

         2025 4 28   21 h 41 min 45 s   UTC 

Matrix ITRF -> ICRF: 

-0.99924348221133         0.03881247872399         0.00246064086674 
-0.03881250424200        -0.99924651018446         0.00003739856122 
0.00246023832977        -0.00005813336554         0.99999697191935 

Quaternion (q1, q2, q3, q4):

        -0.01940991707586         0.00123045253596        -0.00000518468175         0.99981085265103

Transformation coordinate M from the international terrestrial reference system (ITRF) to the international celestial reference frame (ICRF) : Celestial coordinates ( X Y Z) = M x Terrestrial coordinates ( x y z ) and associated quaternion of rotation (Bizouard et Cheng, 2023). . Compution of Celestial Pole coordinates (X,Y), Earth rotation angle, Celestial Intermediate Origin locator, Terrestrial Intermediate Origin locator are performed by FORTRAN programs of the SOFA IAU library, consistent with the IAU 2000/2006 resolutions.

from 1962 to the current week the transformation can include the interpolated EOP of the daily IERS combined series C04, as well as diurnal and semidiurnal variations in UT1 and polar motion produced by oceanic tides (IERS 2000 conventions). Accuracy is 0.05 mas (milli-arc-seconds), corresponding to 2.5 10^-10rad.
from the current week to 6 months afterthe matrix is computed from the prediction of the polar motion and UT1-UTC.
outside the range [1962, current week+ 6 months prediction] the rotation matrix is restricted to the diurnal rotation and the precession-nutation model IAU 2000
the last digit (14) of the matrix element corresponds to the 10^-14 radian level or 2 10^-6 mas or a datation uncertainty of 0.14 nano seconds/1.6 10^-15 day (in reason of the diurnal rotation)