EarthOrientation

class ssapy.body.EarthOrientation(recalc_threshold=3600.0)

Bases: object

Orientation of earth in GCRF. This is a callable class that returns the orientation matrix at a given time.

Parameters:

recalc_threshold (float) – Seconds after which the precession-nutation matrix and UT1 - TT are recomputed; Earth rotation itself is evaluated at every call. Default 1 hour, which bounds the frame error at 0.003 arcsec. The previous 30-day default let the frame drift 1.0 arcsec in a week and 5.1 arcsec in 29 days (172 m at 7000 km, 1 km at GEO).

Methods Summary

__call__(t[, _E])

Return the orientation matrix at time t.

Methods Documentation

__call__(t, _E=None)

Return the orientation matrix at time t.

Parameters:

t (float) – Time in GPS seconds.

Returns:

E – Orientation matrix at time t.

Return type:

numpy.ndarray