source: trunk/FACT++/erfa/src/tcgtt.c@ 18348

Last change on this file since 18348 was 18348, checked in by tbretz, 9 years ago
File size: 4.3 KB
Line 
1#include "erfa.h"
2
3int eraTcgtt(double tcg1, double tcg2, double *tt1, double *tt2)
4/*
5** - - - - - - - - -
6** e r a T c g t t
7** - - - - - - - - -
8**
9** Time scale transformation: Geocentric Coordinate Time, TCG, to
10** Terrestrial Time, TT.
11**
12** Given:
13** tcg1,tcg2 double TCG 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** tcg1+tcg2 is Julian Date, apportioned in any convenient way
24** between the two arguments, for example where tcg1 is the Julian
25** Day Number and tcg22 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** IAU 2000 Resolution B1.9
34**
35** Copyright (C) 2013-2015, NumFOCUS Foundation.
36** Derived, with permission, from the SOFA library. See notes at end of file.
37*/
38{
39
40/* 1977 Jan 1 00:00:32.184 TT, as MJD */
41 static const double t77t = ERFA_DJM77 + ERFA_TTMTAI/ERFA_DAYSEC;
42
43/* Result, safeguarding precision. */
44 if ( tcg1 > tcg2 ) {
45 *tt1 = tcg1;
46 *tt2 = tcg2 - ( ( tcg1 - ERFA_DJM0 ) + ( tcg2 - t77t ) ) * ERFA_ELG;
47 } else {
48 *tt1 = tcg1 - ( ( tcg2 - ERFA_DJM0 ) + ( tcg1 - t77t ) ) * ERFA_ELG;
49 *tt2 = tcg2;
50 }
51
52/* OK status. */
53 return 0;
54
55}
56/*----------------------------------------------------------------------
57**
58**
59** Copyright (C) 2013-2015, NumFOCUS Foundation.
60** All rights reserved.
61**
62** This library is derived, with permission, from the International
63** Astronomical Union's "Standards of Fundamental Astronomy" library,
64** available from http://www.iausofa.org.
65**
66** The ERFA version is intended to retain identical functionality to
67** the SOFA library, but made distinct through different function and
68** file names, as set out in the SOFA license conditions. The SOFA
69** original has a role as a reference standard for the IAU and IERS,
70** and consequently redistribution is permitted only in its unaltered
71** state. The ERFA version is not subject to this restriction and
72** therefore can be included in distributions which do not support the
73** concept of "read only" software.
74**
75** Although the intent is to replicate the SOFA API (other than
76** replacement of prefix names) and results (with the exception of
77** bugs; any that are discovered will be fixed), SOFA is not
78** responsible for any errors found in this version of the library.
79**
80** If you wish to acknowledge the SOFA heritage, please acknowledge
81** that you are using a library derived from SOFA, rather than SOFA
82** itself.
83**
84**
85** TERMS AND CONDITIONS
86**
87** Redistribution and use in source and binary forms, with or without
88** modification, are permitted provided that the following conditions
89** are met:
90**
91** 1 Redistributions of source code must retain the above copyright
92** notice, this list of conditions and the following disclaimer.
93**
94** 2 Redistributions in binary form must reproduce the above copyright
95** notice, this list of conditions and the following disclaimer in
96** the documentation and/or other materials provided with the
97** distribution.
98**
99** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
100** the International Astronomical Union nor the names of its
101** contributors may be used to endorse or promote products derived
102** from this software without specific prior written permission.
103**
104** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
105** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
106** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
107** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
108** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
109** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
110** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
111** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
112** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
113** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
114** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
115** POSSIBILITY OF SUCH DAMAGE.
116**
117*/
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