FACT++  1.0
era00.c
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1 #include "erfa.h"
2 
3 double eraEra00(double dj1, double dj2)
4 /*
5 ** - - - - - - - - -
6 ** e r a E r a 0 0
7 ** - - - - - - - - -
8 **
9 ** Earth rotation angle (IAU 2000 model).
10 **
11 ** Given:
12 ** dj1,dj2 double UT1 as a 2-part Julian Date (see note)
13 **
14 ** Returned (function value):
15 ** double Earth rotation angle (radians), range 0-2pi
16 **
17 ** Notes:
18 **
19 ** 1) The UT1 date dj1+dj2 is a Julian Date, apportioned in any
20 ** convenient way between the arguments dj1 and dj2. For example,
21 ** JD(UT1)=2450123.7 could be expressed in any of these ways,
22 ** among others:
23 **
24 ** dj1 dj2
25 **
26 ** 2450123.7 0.0 (JD method)
27 ** 2451545.0 -1421.3 (J2000 method)
28 ** 2400000.5 50123.2 (MJD method)
29 ** 2450123.5 0.2 (date & time method)
30 **
31 ** The JD method is the most natural and convenient to use in
32 ** cases where the loss of several decimal digits of resolution
33 ** is acceptable. The J2000 and MJD methods are good compromises
34 ** between resolution and convenience. The date & time method is
35 ** best matched to the algorithm used: maximum precision is
36 ** delivered when the dj1 argument is for 0hrs UT1 on the day in
37 ** question and the dj2 argument lies in the range 0 to 1, or vice
38 ** versa.
39 **
40 ** 2) The algorithm is adapted from Expression 22 of Capitaine et al.
41 ** 2000. The time argument has been expressed in days directly,
42 ** and, to retain precision, integer contributions have been
43 ** eliminated. The same formulation is given in IERS Conventions
44 ** (2003), Chap. 5, Eq. 14.
45 **
46 ** Called:
47 ** eraAnp normalize angle into range 0 to 2pi
48 **
49 ** References:
50 **
51 ** Capitaine N., Guinot B. and McCarthy D.D, 2000, Astron.
52 ** Astrophys., 355, 398-405.
53 **
54 ** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
55 ** IERS Technical Note No. 32, BKG (2004)
56 **
57 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
58 ** Derived, with permission, from the SOFA library. See notes at end of file.
59 */
60 {
61  double d1, d2, t, f, theta;
62 
63 /* Days since fundamental epoch. */
64  if (dj1 < dj2) {
65  d1 = dj1;
66  d2 = dj2;
67  } else {
68  d1 = dj2;
69  d2 = dj1;
70  }
71  t = d1 + (d2- ERFA_DJ00);
72 
73 /* Fractional part of T (days). */
74  f = fmod(d1, 1.0) + fmod(d2, 1.0);
75 
76 /* Earth rotation angle at this UT1. */
77  theta = eraAnp(ERFA_D2PI * (f + 0.7790572732640
78  + 0.00273781191135448 * t));
79 
80  return theta;
81 
82 }
83 /*----------------------------------------------------------------------
84 **
85 **
86 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
87 ** All rights reserved.
88 **
89 ** This library is derived, with permission, from the International
90 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
91 ** available from http://www.iausofa.org.
92 **
93 ** The ERFA version is intended to retain identical functionality to
94 ** the SOFA library, but made distinct through different function and
95 ** file names, as set out in the SOFA license conditions. The SOFA
96 ** original has a role as a reference standard for the IAU and IERS,
97 ** and consequently redistribution is permitted only in its unaltered
98 ** state. The ERFA version is not subject to this restriction and
99 ** therefore can be included in distributions which do not support the
100 ** concept of "read only" software.
101 **
102 ** Although the intent is to replicate the SOFA API (other than
103 ** replacement of prefix names) and results (with the exception of
104 ** bugs; any that are discovered will be fixed), SOFA is not
105 ** responsible for any errors found in this version of the library.
106 **
107 ** If you wish to acknowledge the SOFA heritage, please acknowledge
108 ** that you are using a library derived from SOFA, rather than SOFA
109 ** itself.
110 **
111 **
112 ** TERMS AND CONDITIONS
113 **
114 ** Redistribution and use in source and binary forms, with or without
115 ** modification, are permitted provided that the following conditions
116 ** are met:
117 **
118 ** 1 Redistributions of source code must retain the above copyright
119 ** notice, this list of conditions and the following disclaimer.
120 **
121 ** 2 Redistributions in binary form must reproduce the above copyright
122 ** notice, this list of conditions and the following disclaimer in
123 ** the documentation and/or other materials provided with the
124 ** distribution.
125 **
126 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
127 ** the International Astronomical Union nor the names of its
128 ** contributors may be used to endorse or promote products derived
129 ** from this software without specific prior written permission.
130 **
131 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
132 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
133 ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
134 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
135 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
136 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
137 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
138 ** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
139 ** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
140 ** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
141 ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
142 ** POSSIBILITY OF SUCH DAMAGE.
143 **
144 */
ERFA_DJ00
#define ERFA_DJ00
Definition: erfam.h:87
eraEra00
double eraEra00(double dj1, double dj2)
Definition: era00.c:3
ERFA_D2PI
#define ERFA_D2PI
Definition: erfam.h:48
t
TT t
Definition: test_client.c:26
eraAnp
double eraAnp(double a)
Definition: anp.c:3