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era.utcut1.md

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eraUtcut1

[rv, ut11, ut12] = ERFA.utcut1(utc1, utc2, dut1)

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