File Coverage

erfasrc/src/tcbtdb.c
Criterion Covered Total %
statement 0 9 0.0
branch 0 2 0.0
condition n/a
subroutine n/a
pod n/a
total 0 11 0.0


line stmt bran cond sub pod time code
1             #include "erfa.h"
2              
3 0           int eraTcbtdb(double tcb1, double tcb2, double *tdb1, double *tdb2)
4             /*
5             ** - - - - - - - - - -
6             ** e r a T c b t d b
7             ** - - - - - - - - - -
8             **
9             ** Time scale transformation: Barycentric Coordinate Time, TCB, to
10             ** Barycentric Dynamical Time, TDB.
11             **
12             ** Given:
13             ** tcb1,tcb2 double TCB as a 2-part Julian Date
14             **
15             ** Returned:
16             ** tdb1,tdb2 double TDB as a 2-part Julian Date
17             **
18             ** Returned (function value):
19             ** int status: 0 = OK
20             **
21             ** Notes:
22             **
23             ** 1) tcb1+tcb2 is Julian Date, apportioned in any convenient way
24             ** between the two arguments, for example where tcb1 is the Julian
25             ** Day Number and tcb2 is the fraction of a day. The returned
26             ** tdb1,tdb2 follow suit.
27             **
28             ** 2) The 2006 IAU General Assembly introduced a conventional linear
29             ** transformation between TDB and TCB. This transformation
30             ** compensates for the drift between TCB and terrestrial time TT,
31             ** and keeps TDB approximately centered on TT. Because the
32             ** relationship between TT and TCB depends on the adopted solar
33             ** system ephemeris, the degree of alignment between TDB and TT over
34             ** long intervals will vary according to which ephemeris is used.
35             ** Former definitions of TDB attempted to avoid this problem by
36             ** stipulating that TDB and TT should differ only by periodic
37             ** effects. This is a good description of the nature of the
38             ** relationship but eluded precise mathematical formulation. The
39             ** conventional linear relationship adopted in 2006 sidestepped
40             ** these difficulties whilst delivering a TDB that in practice was
41             ** consistent with values before that date.
42             **
43             ** 3) TDB is essentially the same as Teph, the time argument for the
44             ** JPL solar system ephemerides.
45             **
46             ** Reference:
47             **
48             ** IAU 2006 Resolution B3
49             **
50             ** Copyright (C) 2013-2020, NumFOCUS Foundation.
51             ** Derived, with permission, from the SOFA library. See notes at end of file.
52             */
53             {
54              
55             /* 1977 Jan 1 00:00:32.184 TT, as two-part JD */
56             static const double t77td = ERFA_DJM0 + ERFA_DJM77;
57             static const double t77tf = ERFA_TTMTAI/ERFA_DAYSEC;
58              
59             /* TDB (days) at TAI 1977 Jan 1.0 */
60             static const double tdb0 = ERFA_TDB0/ERFA_DAYSEC;
61              
62             double d;
63              
64              
65             /* Result, safeguarding precision. */
66 0 0         if ( fabs(tcb1) > fabs(tcb2) ) {
67 0           d = tcb1 - t77td;
68 0           *tdb1 = tcb1;
69 0           *tdb2 = tcb2 + tdb0 - ( d + ( tcb2 - t77tf ) ) * ERFA_ELB;
70             } else {
71 0           d = tcb2 - t77td;
72 0           *tdb1 = tcb1 + tdb0 - ( d + ( tcb1 - t77tf ) ) * ERFA_ELB;
73 0           *tdb2 = tcb2;
74             }
75              
76             /* Status (always OK). */
77 0           return 0;
78              
79             }
80             /*----------------------------------------------------------------------
81             **
82             **
83             ** Copyright (C) 2013-2020, NumFOCUS Foundation.
84             ** All rights reserved.
85             **
86             ** This library is derived, with permission, from the International
87             ** Astronomical Union's "Standards of Fundamental Astronomy" library,
88             ** available from http://www.iausofa.org.
89             **
90             ** The ERFA version is intended to retain identical functionality to
91             ** the SOFA library, but made distinct through different function and
92             ** file names, as set out in the SOFA license conditions. The SOFA
93             ** original has a role as a reference standard for the IAU and IERS,
94             ** and consequently redistribution is permitted only in its unaltered
95             ** state. The ERFA version is not subject to this restriction and
96             ** therefore can be included in distributions which do not support the
97             ** concept of "read only" software.
98             **
99             ** Although the intent is to replicate the SOFA API (other than
100             ** replacement of prefix names) and results (with the exception of
101             ** bugs; any that are discovered will be fixed), SOFA is not
102             ** responsible for any errors found in this version of the library.
103             **
104             ** If you wish to acknowledge the SOFA heritage, please acknowledge
105             ** that you are using a library derived from SOFA, rather than SOFA
106             ** itself.
107             **
108             **
109             ** TERMS AND CONDITIONS
110             **
111             ** Redistribution and use in source and binary forms, with or without
112             ** modification, are permitted provided that the following conditions
113             ** are met:
114             **
115             ** 1 Redistributions of source code must retain the above copyright
116             ** notice, this list of conditions and the following disclaimer.
117             **
118             ** 2 Redistributions in binary form must reproduce the above copyright
119             ** notice, this list of conditions and the following disclaimer in
120             ** the documentation and/or other materials provided with the
121             ** distribution.
122             **
123             ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
124             ** the International Astronomical Union nor the names of its
125             ** contributors may be used to endorse or promote products derived
126             ** from this software without specific prior written permission.
127             **
128             ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
129             ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
130             ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
131             ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
132             ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
133             ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
134             ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
135             ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
136             ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
137             ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
138             ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
139             ** POSSIBILITY OF SUCH DAMAGE.
140             **
141             */