source: trunk/FACT++/erfa/src/taitt.c@ 18403

Last change on this file since 18403 was 18348, checked in by tbretz, 9 years ago
File size: 4.3 KB
Line 
1#include "erfa.h"
2
3int eraTaitt(double tai1, double tai2, double *tt1, double *tt2)
4/*
5** - - - - - - - - -
6** e r a T a i t t
7** - - - - - - - - -
8**
9** Time scale transformation: International Atomic Time, TAI, to
10** Terrestrial Time, TT.
11**
12** Given:
13** tai1,tai2 double TAI as a 2-part Julian Date
14**
15** Returned:
16** tt1,tt2 double TT as a 2-part Julian Date
17**
18** Returned (function value):
19** int status: 0 = OK
20**
21** Note:
22**
23** tai1+tai2 is Julian Date, apportioned in any convenient way
24** between the two arguments, for example where tai1 is the Julian
25** Day Number and tai2 is the fraction of a day. The returned
26** tt1,tt2 follow 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) 2013-2015, 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/* Result, safeguarding precision. */
45 if ( tai1 > tai2 ) {
46 *tt1 = tai1;
47 *tt2 = tai2 + dtat;
48 } else {
49 *tt1 = tai1 + dtat;
50 *tt2 = tai2;
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*/
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