FACT++  1.0
nut06a.c
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1 #include "erfa.h"
2 
3 void eraNut06a(double date1, double date2, double *dpsi, double *deps)
4 /*
5 ** - - - - - - - - - -
6 ** e r a N u t 0 6 a
7 ** - - - - - - - - - -
8 **
9 ** IAU 2000A nutation with adjustments to match the IAU 2006
10 ** precession.
11 **
12 ** Given:
13 ** date1,date2 double TT as a 2-part Julian Date (Note 1)
14 **
15 ** Returned:
16 ** dpsi,deps double nutation, luni-solar + planetary (Note 2)
17 **
18 ** Notes:
19 **
20 ** 1) The TT date date1+date2 is a Julian Date, apportioned in any
21 ** convenient way between the two arguments. For example,
22 ** JD(TT)=2450123.7 could be expressed in any of these ways,
23 ** among others:
24 **
25 ** date1 date2
26 **
27 ** 2450123.7 0.0 (JD method)
28 ** 2451545.0 -1421.3 (J2000 method)
29 ** 2400000.5 50123.2 (MJD method)
30 ** 2450123.5 0.2 (date & time method)
31 **
32 ** The JD method is the most natural and convenient to use in
33 ** cases where the loss of several decimal digits of resolution
34 ** is acceptable. The J2000 method is best matched to the way
35 ** the argument is handled internally and will deliver the
36 ** optimum resolution. The MJD method and the date & time methods
37 ** are both good compromises between resolution and convenience.
38 **
39 ** 2) The nutation components in longitude and obliquity are in radians
40 ** and with respect to the mean equinox and ecliptic of date,
41 ** IAU 2006 precession model (Hilton et al. 2006, Capitaine et al.
42 ** 2005).
43 **
44 ** 3) The function first computes the IAU 2000A nutation, then applies
45 ** adjustments for (i) the consequences of the change in obliquity
46 ** from the IAU 1980 ecliptic to the IAU 2006 ecliptic and (ii) the
47 ** secular variation in the Earth's dynamical form factor J2.
48 **
49 ** 4) The present function provides classical nutation, complementing
50 ** the IAU 2000 frame bias and IAU 2006 precession. It delivers a
51 ** pole which is at current epochs accurate to a few tens of
52 ** microarcseconds, apart from the free core nutation.
53 **
54 ** Called:
55 ** eraNut00a nutation, IAU 2000A
56 **
57 ** References:
58 **
59 ** Chapront, J., Chapront-Touze, M. & Francou, G. 2002,
60 ** Astron.Astrophys. 387, 700
61 **
62 ** Lieske, J.H., Lederle, T., Fricke, W. & Morando, B. 1977,
63 ** Astron.Astrophys. 58, 1-16
64 **
65 ** Mathews, P.M., Herring, T.A., Buffet, B.A. 2002, J.Geophys.Res.
66 ** 107, B4. The MHB_2000 code itself was obtained on 9th September
67 ** 2002 from ftp//maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
68 **
69 ** Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
70 ** Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
71 **
72 ** Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
73 ** Astron.Astrophys.Supp.Ser. 135, 111
74 **
75 ** Wallace, P.T., "Software for Implementing the IAU 2000
76 ** Resolutions", in IERS Workshop 5.1 (2002)
77 **
78 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
79 ** Derived, with permission, from the SOFA library. See notes at end of file.
80 */
81 {
82  double t, fj2, dp, de;
83 
84 /* Interval between fundamental date J2000.0 and given date (JC). */
85  t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC;
86 
87 /* Factor correcting for secular variation of J2. */
88  fj2 = -2.7774e-6 * t;
89 
90 /* Obtain IAU 2000A nutation. */
91  eraNut00a(date1, date2, &dp, &de);
92 
93 /* Apply P03 adjustments (Wallace & Capitaine, 2006, Eqs.5). */
94  *dpsi = dp + dp * (0.4697e-6 + fj2);
95  *deps = de + de * fj2;
96 
97  return;
98 
99 }
100 /*----------------------------------------------------------------------
101 **
102 **
103 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
104 ** All rights reserved.
105 **
106 ** This library is derived, with permission, from the International
107 ** Astronomical Union's "Standards of Fundamental Astronomy" library,
108 ** available from http://www.iausofa.org.
109 **
110 ** The ERFA version is intended to retain identical functionality to
111 ** the SOFA library, but made distinct through different function and
112 ** file names, as set out in the SOFA license conditions. The SOFA
113 ** original has a role as a reference standard for the IAU and IERS,
114 ** and consequently redistribution is permitted only in its unaltered
115 ** state. The ERFA version is not subject to this restriction and
116 ** therefore can be included in distributions which do not support the
117 ** concept of "read only" software.
118 **
119 ** Although the intent is to replicate the SOFA API (other than
120 ** replacement of prefix names) and results (with the exception of
121 ** bugs; any that are discovered will be fixed), SOFA is not
122 ** responsible for any errors found in this version of the library.
123 **
124 ** If you wish to acknowledge the SOFA heritage, please acknowledge
125 ** that you are using a library derived from SOFA, rather than SOFA
126 ** itself.
127 **
128 **
129 ** TERMS AND CONDITIONS
130 **
131 ** Redistribution and use in source and binary forms, with or without
132 ** modification, are permitted provided that the following conditions
133 ** are met:
134 **
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137 **
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142 **
143 ** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
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147 **
148 ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
149 ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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152 ** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
153 ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
154 ** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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ERFA_DJ00
#define ERFA_DJ00
Definition: erfam.h:87
ERFA_DJC
#define ERFA_DJC
Definition: erfam.h:81
eraNut00a
void eraNut00a(double date1, double date2, double *dpsi, double *deps)
Definition: nut00a.c:3
eraNut06a
void eraNut06a(double date1, double date2, double *dpsi, double *deps)
Definition: nut06a.c:3
t
TT t
Definition: test_client.c:26