heyoka.model.dY

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heyoka.model.dY#

heyoka.model.dY(time_expr: expression = heyoka.time, eop_data: eop_data = eop_data()) → expression#

Correction to the Earth’s precession/nutation model (y component).

Added in version 7.3.0.

This function will return an expression representing the \(y\) coordinate of the correction to the Earth’s precession-nutation model (IAU 2000/2006) as a function of the input time expression time_expr. time_expr is expected to represent the number of Julian centuries elapsed since the epoch of J2000 in the terrestrial time scale (TT). eop_data is the Earth orientation parameters dataset to be used for the computation.

This quantity is modelled as a piecewise linear function of time, where the switch points are given by the dates in eop_data. Evaluation outside the dates range of eop_data will produce a value of NaN.

The return value is expressed in radians.

Parameters:

  • time_expr – the input time expression.

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

Returns:

an expression for the y component of the correction to the Earth’s precession/nutation model.

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