heyoka.model.rot_icrs_itrs

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heyoka.model.rot_icrs_itrs#

heyoka.model.rot_icrs_itrs(xyz: Iterable[expression], time_expr: expression = heyoka.time, thresh: float = 1e-06, eop_data: eop_data = eop_data()) → list[expression]#

Rotation from ICRS to ITRS.

Added in version 7.3.0.

This function will rotate the input Cartesian coordinates xyz from the axes of the ICRS frame to the axes of the ITRS frame.

While the orientation of the ICRS is fixed in inertial space, the orientation of the ITRS is fixed relative to the Earth, and thus the rotation depends on the input time time_expr (which is expected to represent the number of Julian centuries elapsed since the epoch of J2000 in the terrestrial time scale (TT)).

The rotation also requires in input an Earth orientation parameters dataset eop_data and a truncation threshold thresh for the IAU2000/2006 precession-nutation theory. Please see the documentation of eop_data and iau2006() for more information.

Parameters:

  • xyz – the input Cartesian coordinates.

  • time_expr – the input time expression.

  • thresh – the truncation threshold for the IAU2000/2006 theory.

  • eop_data – the EOP data to be used for the computation.

Returns:

the rotated Cartesian coordinates.

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