Function lupnt::RotPolarMotion

Function Documentation

Mat3 lupnt::RotPolarMotion(Real t_tdb)

Returns the polar-motion rotation matrix R_po at epoch t_tdb, which rotates a vector from the Earth-fixed pseudo-ITRF (post-sidereal-rotation) frame into the true ITRF frame by the IERS polar-motion angles (x_pole, y_pole) and the TIO locator s’, i.e. v_ITRF = R_po * v_pseudo_itrf.

If InitFrameConversionFromSpice has fitted a SPICE-derived EOP model (see ComputeEopFromSpice) covering t_tdb, the fitted x_pole/y_pole are used in place of the loaded IERS EOP table.

Used internally by GcrfToItrf/ItrfToGcrf as the final stage of R_GcrfToItrf = R_po * R_s * R_pn. If InitFrameConversionFromSpice has fitted a SPICE-derived EOP model covering t_tdb, the fitted x_pole/y_pole are used in place of the loaded IERS EOP table.

Note

Astrodynamics Convention & Modeling Reference, Version 1.1, Page 36

Parameters:

t_tdb – Epoch [s, TDB since J2000]

Returns:

3x3 polar-motion rotation matrix R_po (dimensionless)