FACT++  1.0
bi00.c
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1 #include "erfa.h"
2 
3 void eraBi00(double *dpsibi, double *depsbi, double *dra)
4 /*
5 ** - - - - - - - -
6 ** e r a B i 0 0
7 ** - - - - - - - -
8 **
9 ** Frame bias components of IAU 2000 precession-nutation models (part
10 ** of MHB2000 with additions).
11 **
12 ** Returned:
13 ** dpsibi,depsbi double longitude and obliquity corrections
14 ** dra double the ICRS RA of the J2000.0 mean equinox
15 **
16 ** Notes:
17 **
18 ** 1) The frame bias corrections in longitude and obliquity (radians)
19 ** are required in order to correct for the offset between the GCRS
20 ** pole and the mean J2000.0 pole. They define, with respect to the
21 ** GCRS frame, a J2000.0 mean pole that is consistent with the rest
22 ** of the IAU 2000A precession-nutation model.
23 **
24 ** 2) In addition to the displacement of the pole, the complete
25 ** description of the frame bias requires also an offset in right
26 ** ascension. This is not part of the IAU 2000A model, and is from
27 ** Chapront et al. (2002). It is returned in radians.
28 **
29 ** 3) This is a supplemented implementation of one aspect of the IAU
30 ** 2000A nutation model, formally adopted by the IAU General
31 ** Assembly in 2000, namely MHB2000 (Mathews et al. 2002).
32 **
33 ** References:
34 **
35 ** Chapront, J., Chapront-Touze, M. & Francou, G., Astron.
36 ** Astrophys., 387, 700, 2002.
37 **
38 ** Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
39 ** and precession New nutation series for nonrigid Earth and
40 ** insights into the Earth's interior", J.Geophys.Res., 107, B4,
41 ** 2002. The MHB2000 code itself was obtained on 9th September 2002
42 ** from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
43 **
44 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
45 ** Derived, with permission, from the SOFA library. See notes at end of file.
46 */
47 {
48 /* The frame bias corrections in longitude and obliquity */
49  const double DPBIAS = -0.041775 * ERFA_DAS2R,
50  DEBIAS = -0.0068192 * ERFA_DAS2R;
51 
52 /* The ICRS RA of the J2000.0 equinox (Chapront et al., 2002) */
53  const double DRA0 = -0.0146 * ERFA_DAS2R;
54 
55 /* Return the results (which are fixed). */
56  *dpsibi = DPBIAS;
57  *depsbi = DEBIAS;
58  *dra = DRA0;
59 
60  return;
61 
62 }
63 /*----------------------------------------------------------------------
64 **
65 **
66 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
67 ** All rights reserved.
68 **
69 ** This library is derived, with permission, from the International
70 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
71 ** available from http://www.iausofa.org.
72 **
73 ** The ERFA version is intended to retain identical functionality to
74 ** the SOFA library, but made distinct through different function and
75 ** file names, as set out in the SOFA license conditions. The SOFA
76 ** original has a role as a reference standard for the IAU and IERS,
77 ** and consequently redistribution is permitted only in its unaltered
78 ** state. The ERFA version is not subject to this restriction and
79 ** therefore can be included in distributions which do not support the
80 ** concept of "read only" software.
81 **
82 ** Although the intent is to replicate the SOFA API (other than
83 ** replacement of prefix names) and results (with the exception of
84 ** bugs; any that are discovered will be fixed), SOFA is not
85 ** responsible for any errors found in this version of the library.
86 **
87 ** If you wish to acknowledge the SOFA heritage, please acknowledge
88 ** that you are using a library derived from SOFA, rather than SOFA
89 ** itself.
90 **
91 **
92 ** TERMS AND CONDITIONS
93 **
94 ** Redistribution and use in source and binary forms, with or without
95 ** modification, are permitted provided that the following conditions
96 ** are met:
97 **
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99 ** notice, this list of conditions and the following disclaimer.
100 **
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105 **
106 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
107 ** the International Astronomical Union nor the names of its
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110 **
111 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
112 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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114 ** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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124 */
ERFA_DAS2R
#define ERFA_DAS2R
Definition: erfam.h:60
eraBi00
void eraBi00(double *dpsibi, double *depsbi, double *dra)
Definition: bi00.c:3