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eraEors

rv = ERFA.eors(rnpb, s)

Equation of the origins, given the classical NPB matrix and the quantity s.

Given:

   rnpb  double[3][3]  classical nutation x precession x bias matrix
   s     double        the quantity s (the CIO locator) in radians

Returned (function value):

         double        the equation of the origins in radians

Notes:

  1. The equation of the origins is the distance between the true equinox and the celestial intermediate origin and, equivalently, the difference between Earth rotation angle and Greenwich apparent sidereal time (ERA-GST). It comprises the precession (since J2000.0) in right ascension plus the equation of the equinoxes (including the small correction terms).

  2. The algorithm is from Wallace & Capitaine (2006).

References:

Capitaine, N. & Wallace, P.T., 2006, Astron.Astrophys. 450, 855

Wallace, P. & Capitaine, N., 2006, Astron.Astrophys. 459, 981

This revision: 2021 May 11

Copyright (C) 2013-2021, NumFOCUS Foundation. Derived, with permission, from the SOFA library.