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eraNumat

rmatn = ERFA.numat(epsa, dpsi, deps)

Form the matrix of nutation.

Given:

   epsa        double         mean obliquity of date (Note 1)
   dpsi,deps   double         nutation (Note 2)

Returned:

   rmatn       double[3][3]   nutation matrix (Note 3)

Notes:

  1. The supplied mean obliquity epsa, must be consistent with the precession-nutation models from which dpsi and deps were obtained.

  2. The caller is responsible for providing the nutation components; they are in longitude and obliquity, in radians and are with respect to the equinox and ecliptic of date.

  3. The matrix operates in the sense V(true) = rmatn * V(mean), where the p-vector V(true) is with respect to the true equatorial triad of date and the p-vector V(mean) is with respect to the mean equatorial triad of date.

Called:

   eraIr        initialize r-matrix to identity
   eraRx        rotate around X-axis
   eraRz        rotate around Z-axis

Reference:

Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992), Section 3.222-3 (p114).

This revision: 2021 May 11

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