FACT++  1.0
ttut1.c
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1 #include "erfa.h"
2 
3 int eraTtut1(double tt1, double tt2, double dt,
4  double *ut11, double *ut12)
5 /*
6 ** - - - - - - - - -
7 ** e r a T t u t 1
8 ** - - - - - - - - -
9 **
10 ** Time scale transformation: Terrestrial Time, TT, to Universal Time,
11 ** UT1.
12 **
13 ** Given:
14 ** tt1,tt2 double TT as a 2-part Julian Date
15 ** dt double TT-UT1 in seconds
16 **
17 ** Returned:
18 ** ut11,ut12 double UT1 as a 2-part Julian Date
19 **
20 ** Returned (function value):
21 ** int status: 0 = OK
22 **
23 ** Notes:
24 **
25 ** 1) tt1+tt2 is Julian Date, apportioned in any convenient way between
26 ** the two arguments, for example where tt1 is the Julian Day Number
27 ** and tt2 is the fraction of a day. The returned ut11,ut12 follow
28 ** suit.
29 **
30 ** 2) The argument dt is classical Delta T.
31 **
32 ** Reference:
33 **
34 ** Explanatory Supplement to the Astronomical Almanac,
35 ** P. Kenneth Seidelmann (ed), University Science Books (1992)
36 **
37 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
38 ** Derived, with permission, from the SOFA library. See notes at end of file.
39 */
40 {
41  double dtd;
42 
43 /* Result, safeguarding precision. */
44  dtd = dt / ERFA_DAYSEC;
45  if ( tt1 > tt2 ) {
46  *ut11 = tt1;
47  *ut12 = tt2 - dtd;
48  } else {
49  *ut11 = tt1 - dtd;
50  *ut12 = tt2;
51  }
52 
53 /* Status (always OK). */
54  return 0;
55 
56 }
57 /*----------------------------------------------------------------------
58 **
59 **
60 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
61 ** All rights reserved.
62 **
63 ** This library is derived, with permission, from the International
64 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
65 ** available from http://www.iausofa.org.
66 **
67 ** The ERFA version is intended to retain identical functionality to
68 ** the SOFA library, but made distinct through different function and
69 ** file names, as set out in the SOFA license conditions. The SOFA
70 ** original has a role as a reference standard for the IAU and IERS,
71 ** and consequently redistribution is permitted only in its unaltered
72 ** state. The ERFA version is not subject to this restriction and
73 ** therefore can be included in distributions which do not support the
74 ** concept of "read only" software.
75 **
76 ** Although the intent is to replicate the SOFA API (other than
77 ** replacement of prefix names) and results (with the exception of
78 ** bugs; any that are discovered will be fixed), SOFA is not
79 ** responsible for any errors found in this version of the library.
80 **
81 ** If you wish to acknowledge the SOFA heritage, please acknowledge
82 ** that you are using a library derived from SOFA, rather than SOFA
83 ** itself.
84 **
85 **
86 ** TERMS AND CONDITIONS
87 **
88 ** Redistribution and use in source and binary forms, with or without
89 ** modification, are permitted provided that the following conditions
90 ** are met:
91 **
92 ** 1 Redistributions of source code must retain the above copyright
93 ** notice, this list of conditions and the following disclaimer.
94 **
95 ** 2 Redistributions in binary form must reproduce the above copyright
96 ** notice, this list of conditions and the following disclaimer in
97 ** the documentation and/or other materials provided with the
98 ** distribution.
99 **
100 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
101 ** the International Astronomical Union nor the names of its
102 ** contributors may be used to endorse or promote products derived
103 ** from this software without specific prior written permission.
104 **
105 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
106 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
107 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
108 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
109 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
110 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
111 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
112 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
113 ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
114 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
115 ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
116 ** POSSIBILITY OF SUCH DAMAGE.
117 **
118 */
eraTtut1
int eraTtut1(double tt1, double tt2, double dt, double *ut11, double *ut12)
Definition: ttut1.c:3
ERFA_DAYSEC
#define ERFA_DAYSEC
Definition: erfam.h:75