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# era00

erfa.era00(dj1, dj2)

  Earth rotation angle (IAU 2000 model).

  Parameters
    dj1 double array
    dj2 double array
  Returns
    c_retval double array

  Notes

  Wraps ERFA function `eraEra00`. The ERFA documentation is:

      - - - - - - - - -
       e r a E r a 0 0
      - - - - - - - - -

      Earth rotation angle (IAU 2000 model).

      Given:
         dj1,dj2   double    UT1 as a 2-part Julian Date (see note)

      Returned (function value):
                   double    Earth rotation angle (radians), range 0-2pi

      Notes:

      1) The UT1 date dj1+dj2 is a Julian Date, apportioned in any
         convenient way between the arguments dj1 and dj2.  For example,
         JD(UT1)=2450123.7 could be expressed in any of these ways,
         among others:

                 dj1            dj2

             2450123.7           0.0       (JD method)
             2451545.0       -1421.3       (J2000 method)
             2400000.5       50123.2       (MJD method)
             2450123.5           0.2       (date & time method)

         The JD method is the most natural and convenient to use in
         cases where the loss of several decimal digits of resolution
         is acceptable.  The J2000 and MJD methods are good compromises
         between resolution and convenience.  The date & time method is
         best matched to the algorithm used:  maximum precision is
         delivered when the dj1 argument is for 0hrs UT1 on the day in
         question and the dj2 argument lies in the range 0 to 1, or vice
         versa.

      2) The algorithm is adapted from Expression 22 of Capitaine et al.
         2000.  The time argument has been expressed in days directly,
         and, to retain precision, integer contributions have been
         eliminated.  The same formulation is given in IERS Conventions
         (2003), Chap. 5, Eq. 14.

      Called:
         eraAnp       normalize angle into range 0 to 2pi

      References:

         Capitaine N., Guinot B. and McCarthy D.D, 2000, Astron.
         Astrophys., 355, 398-405.

         McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
         IERS Technical Note No. 32, BKG (2004)

      This revision:  2021 May 11

      Copyright (C) 2013-2021, NumFOCUS Foundation.
      Derived, with permission, from the SOFA library.  See notes at end of file.