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#include "erfa.h"
int eraUt1utc(double ut11, double ut12, double dut1,
double *utc1, double *utc2)
/*
** - - - - - - - - - -
** e r a U t 1 u t c
** - - - - - - - - - -
**
** Time scale transformation: Universal Time, UT1, to Coordinated
** Universal Time, UTC.
**
** Given:
** ut11,ut12 double UT1 as a 2-part Julian Date (Note 1)
** dut1 double Delta UT1: UT1-UTC in seconds (Note 2)
**
** Returned:
** utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 3,4)
**
** Returned (function value):
** int status: +1 = dubious year (Note 5)
** 0 = OK
** -1 = unacceptable date
**
** Notes:
**
** 1) ut11+ut12 is Julian Date, apportioned in any convenient way
** between the two arguments, for example where ut11 is the Julian
** Day Number and ut12 is the fraction of a day. The returned utc1
** and utc2 form an analogous pair, except that a special convention
** is used, to deal with the problem of leap seconds - see Note 3.
**
** 2) Delta UT1 can be obtained from tabulations provided by the
** International Earth Rotation and Reference Systems Service. The
** value changes abruptly by 1s at a leap second; however, close to
** a leap second the algorithm used here is tolerant of the "wrong"
** choice of value being made.
**
** 3) JD cannot unambiguously represent UTC during a leap second unless
** special measures are taken. The convention in the present
** function is that the returned quasi JD day UTC1+UTC2 represents
** UTC days whether the length is 86399, 86400 or 86401 SI seconds.
**
** 4) The function eraD2dtf can be used to transform the UTC quasi-JD
** into calendar date and clock time, including UTC leap second
** handling.
**
** 5) 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.
**
** Called:
** eraJd2cal JD to Gregorian calendar
** eraDat delta(AT) = TAI-UTC
** eraCal2jd Gregorian calendar to JD
**
** 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)
**
** Copyright (C) 2013-2014, NumFOCUS Foundation.
** Derived, with permission, from the SOFA library. See notes at end of file.
*/
{
int big1;
int i, iy, im, id, js;
double duts, u1, u2, d1, dats1, d2, fd, dats2, ddats, us1, us2, du;
/* UT1-UTC in seconds. */
duts = dut1;
/* Put the two parts of the UT1 into big-first order. */
big1 = ( ut11 >= ut12 );
if ( big1 ) {
u1 = ut11;
u2 = ut12;
} else {
u1 = ut12;
u2 = ut11;
}
/* See if the UT1 can possibly be in a leap-second day. */
d1 = u1;
dats1 = 0;
for ( i = -1; i <= 3; i++ ) {
d2 = u2 + (double) i;
if ( eraJd2cal(d1, d2, &iy, &im, &id, &fd) ) return -1;
js = eraDat(iy, im, id, 0.0, &dats2);
if ( js < 0 ) return -1;
if ( i == - 1 ) dats1 = dats2;
ddats = dats2 - dats1;
if ( fabs(ddats) >= 0.5 ) {
/* Yes, leap second nearby: ensure UT1-UTC is "before" value. */
if ( ddats * duts >= 0 ) duts -= ddats;
/* UT1 for the start of the UTC day that ends in a leap. */
if ( eraCal2jd(iy, im, id, &d1, &d2) ) return -1;
us1 = d1;
us2 = d2 - 1.0 + duts/ERFA_DAYSEC;
/* Is the UT1 after this point? */
du = u1 - us1;
du += u2 - us2;
if ( du > 0 ) {
/* Yes: fraction of the current UTC day that has elapsed. */
fd = du * ERFA_DAYSEC / ( ERFA_DAYSEC + ddats );
/* Ramp UT1-UTC to bring about ERFA's JD(UTC) convention. */
duts += ddats * ( fd <= 1.0 ? fd : 1.0 );
}
/* Done. */
break;
}
dats1 = dats2;
}
/* Subtract the (possibly adjusted) UT1-UTC from UT1 to give UTC. */
u2 -= duts / ERFA_DAYSEC;
/* Result, safeguarding precision. */
if ( big1 ) {
*utc1 = u1;
*utc2 = u2;
} else {
*utc1 = u2;
*utc2 = u1;
}
/* Status. */
return js;
}
/*----------------------------------------------------------------------
**
**
** Copyright (C) 2013-2014, NumFOCUS Foundation.
** All rights reserved.
**
** This library is derived, with permission, from the International
** Astronomical Union's "Standards of Fundamental Astronomy" library,
** available from http://www.iausofa.org.
**
** The ERFA version is intended to retain identical functionality to
** the SOFA library, but made distinct through different function and
** file names, as set out in the SOFA license conditions. The SOFA
** original has a role as a reference standard for the IAU and IERS,
** and consequently redistribution is permitted only in its unaltered
** state. The ERFA version is not subject to this restriction and
** therefore can be included in distributions which do not support the
** concept of "read only" software.
**
** Although the intent is to replicate the SOFA API (other than
** replacement of prefix names) and results (with the exception of
** bugs; any that are discovered will be fixed), SOFA is not
** responsible for any errors found in this version of the library.
**
** If you wish to acknowledge the SOFA heritage, please acknowledge
** that you are using a library derived from SOFA, rather than SOFA
** itself.
**
**
** TERMS AND CONDITIONS
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions
** are met:
**
** 1 Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
**
** 2 Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
**
** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
** the International Astronomical Union nor the names of its
** contributors may be used to endorse or promote products derived
** from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
** POSSIBILITY OF SUCH DAMAGE.
**
*/
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