source: trunk/FACT++/erfa/src/ttut1.c@ 19887

Last change on this file since 19887 was 18921, checked in by tbretz, 7 years ago
Updated to ERFA 1.4.0
File size: 4.2 KB
Line 
1#include "erfa.h"
2
3int 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) 2013-2017, NumFOCUS Foundation.
38** Derived, with permission, from the SOFA library. See notes at end of file.
39*/
40{
41 double dtd;
42
43
44/* Result, safeguarding precision. */
45 dtd = dt / ERFA_DAYSEC;
46 if ( tt1 > tt2 ) {
47 *ut11 = tt1;
48 *ut12 = tt2 - dtd;
49 } else {
50 *ut11 = tt1 - dtd;
51 *ut12 = tt2;
52 }
53
54/* Status (always OK). */
55 return 0;
56
57}
58/*----------------------------------------------------------------------
59**
60**
61** Copyright (C) 2013-2017, NumFOCUS Foundation.
62** All rights reserved.
63**
64** This library is derived, with permission, from the International
65** Astronomical Union's "Standards of Fundamental Astronomy" library,
66** available from http://www.iausofa.org.
67**
68** The ERFA version is intended to retain identical functionality to
69** the SOFA library, but made distinct through different function and
70** file names, as set out in the SOFA license conditions. The SOFA
71** original has a role as a reference standard for the IAU and IERS,
72** and consequently redistribution is permitted only in its unaltered
73** state. The ERFA version is not subject to this restriction and
74** therefore can be included in distributions which do not support the
75** concept of "read only" software.
76**
77** Although the intent is to replicate the SOFA API (other than
78** replacement of prefix names) and results (with the exception of
79** bugs; any that are discovered will be fixed), SOFA is not
80** responsible for any errors found in this version of the library.
81**
82** If you wish to acknowledge the SOFA heritage, please acknowledge
83** that you are using a library derived from SOFA, rather than SOFA
84** itself.
85**
86**
87** TERMS AND CONDITIONS
88**
89** Redistribution and use in source and binary forms, with or without
90** modification, are permitted provided that the following conditions
91** are met:
92**
93** 1 Redistributions of source code must retain the above copyright
94** notice, this list of conditions and the following disclaimer.
95**
96** 2 Redistributions in binary form must reproduce the above copyright
97** notice, this list of conditions and the following disclaimer in
98** the documentation and/or other materials provided with the
99** distribution.
100**
101** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
102** the International Astronomical Union nor the names of its
103** contributors may be used to endorse or promote products derived
104** from this software without specific prior written permission.
105**
106** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
107** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
108** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
109** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
110** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
111** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
112** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
113** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
114** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
115** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
116** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
117** POSSIBILITY OF SUCH DAMAGE.
118**
119*/
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