source: trunk/FACT++/erfa/src/tttai.c@ 19713

Last change on this file since 19713 was 18921, checked in by tbretz, 7 years ago
Updated to ERFA 1.4.0
File size: 4.3 KB
Line 
1#include "erfa.h"
2
3int eraTttai(double tt1, double tt2, double *tai1, double *tai2)
4/*
5** - - - - - - - - -
6** e r a T t t a i
7** - - - - - - - - -
8**
9** Time scale transformation: Terrestrial Time, TT, to International
10** Atomic Time, TAI.
11**
12** Given:
13** tt1,tt2 double TT as a 2-part Julian Date
14**
15** Returned:
16** tai1,tai2 double TAI as a 2-part Julian Date
17**
18** Returned (function value):
19** int status: 0 = OK
20**
21** Note:
22**
23** tt1+tt2 is Julian Date, apportioned in any convenient way between
24** the two arguments, for example where tt1 is the Julian Day Number
25** and tt2 is the fraction of a day. The returned tai1,tai2 follow
26** suit.
27**
28** References:
29**
30** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
31** IERS Technical Note No. 32, BKG (2004)
32**
33** Explanatory Supplement to the Astronomical Almanac,
34** P. Kenneth Seidelmann (ed), University Science Books (1992)
35**
36** Copyright (C) 2013-2017, NumFOCUS Foundation.
37** Derived, with permission, from the SOFA library. See notes at end of file.
38*/
39{
40
41/* TT minus TAI (days). */
42 static const double dtat = ERFA_TTMTAI/ERFA_DAYSEC;
43
44
45/* Result, safeguarding precision. */
46 if ( tt1 > tt2 ) {
47 *tai1 = tt1;
48 *tai2 = tt2 - dtat;
49 } else {
50 *tai1 = tt1 - dtat;
51 *tai2 = 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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