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# utcut1

erfa.utcut1(utc1, utc2, dut1)

  Time scale transformation: Coordinated Universal Time, UTC, to Universal Time, UT1.

  Parameters:
    utc1 double array
    utc2 double array
    dut1 double array
  Returns:
    ut11 double array
    ut12 double array

  Notes

  Wraps ERFA function `eraUtcut1`. The ERFA documentation is:

      - - - - - - - - - -
       e r a U t c u t 1
      - - - - - - - - - -

      Time scale transformation:  Coordinated Universal Time, UTC, to
      Universal Time, UT1.

      Given:
         utc1,utc2  double   UTC as a 2-part quasi Julian Date (Notes 1-4)
         dut1       double   Delta UT1 = UT1-UTC in seconds (Note 5)

      Returned:
         ut11,ut12  double   UT1 as a 2-part Julian Date (Note 6)

      Returned (function value):
                    int      status: +1 = dubious year (Note 3)
                                      0 = OK
                                     -1 = unacceptable date

      Notes:

      1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
         convenient way between the two arguments, for example where utc1
         is the Julian Day Number and utc2 is the fraction of a day.

      2) JD cannot unambiguously represent UTC during a leap second unless
         special measures are taken.  The convention in the present
         function is that the JD day represents UTC days whether the
         length is 86399, 86400 or 86401 SI seconds.

      3) The warning status "dubious year" flags UTCs that predate the
         introduction of the time scale or that are too far in the future
         to be trusted.  See eraDat for further details.

      4) The function eraDtf2d converts from calendar date and time of
         day into 2-part Julian Date, and in the case of UTC implements
         the leap-second-ambiguity convention described above.

      5) Delta UT1 can be obtained from tabulations provided by the
         International Earth Rotation and Reference Systems Service.
         It is the caller's responsibility to supply a dut1 argument
         containing the UT1-UTC value that matches the given UTC.

      6) The returned ut11,ut12 are such that their sum is the UT1 Julian
         Date.

      References:

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

         Explanatory Supplement to the Astronomical Almanac,
         P. Kenneth Seidelmann (ed), University Science Books (1992)

      Called:
         eraJd2cal    JD to Gregorian calendar
         eraDat       delta(AT) = TAI-UTC
         eraUtctai    UTC to TAI
         eraTaiut1    TAI to UT1

      This revision:  2021 May 11

      Copyright (C) 2013-2023, NumFOCUS Foundation.
      Derived, with permission, from the SOFA library.  See notes at end of file.