numat¶

erfa.numat(epsa, dpsi, deps)[source]¶

Form the matrix of nutation.

Parameters:

epsadouble array
dpsidouble array
depsdouble array

Returns:

rmatndouble array

Notes

Wraps ERFA function eraNumat. The ERFA documentation is:

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 e r a N u m a t
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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) 2013-2023, NumFOCUS Foundation.
Derived, with permission, from the SOFA library.  See notes at end of file.

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