heyoka.model.pm_x

Contents

heyoka.model.pm_x#

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

Polar motion (x component).

Added in version 7.3.0.

This function will return an expression representing the \(x\) coordinate of the polar motion 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 x component of the polar motion as a function of time.

Contents