source: trunk/FACT++/erfa/src/nut06a.c@ 18711

Last change on this file since 18711 was 18711, checked in by tbretz, 9 years ago
Updated to ERFA 1.3.0 (no relevant code change except the leap second at the beginning of 2017)
File size: 6.4 KB
Line 
1#include "erfa.h"
2
3void 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) 2013-2016, 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
85/* Interval between fundamental date J2000.0 and given date (JC). */
86 t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC;
87
88/* Factor correcting for secular variation of J2. */
89 fj2 = -2.7774e-6 * t;
90
91/* Obtain IAU 2000A nutation. */
92 eraNut00a(date1, date2, &dp, &de);
93
94/* Apply P03 adjustments (Wallace & Capitaine, 2006, Eqs.5). */
95 *dpsi = dp + dp * (0.4697e-6 + fj2);
96 *deps = de + de * fj2;
97
98 return;
99
100}
101/*----------------------------------------------------------------------
102**
103**
104** Copyright (C) 2013-2016, NumFOCUS Foundation.
105** All rights reserved.
106**
107** This library is derived, with permission, from the International
108** Astronomical Union's "Standards of Fundamental Astronomy" library,
109** available from http://www.iausofa.org.
110**
111** The ERFA version is intended to retain identical functionality to
112** the SOFA library, but made distinct through different function and
113** file names, as set out in the SOFA license conditions. The SOFA
114** original has a role as a reference standard for the IAU and IERS,
115** and consequently redistribution is permitted only in its unaltered
116** state. The ERFA version is not subject to this restriction and
117** therefore can be included in distributions which do not support the
118** concept of "read only" software.
119**
120** Although the intent is to replicate the SOFA API (other than
121** replacement of prefix names) and results (with the exception of
122** bugs; any that are discovered will be fixed), SOFA is not
123** responsible for any errors found in this version of the library.
124**
125** If you wish to acknowledge the SOFA heritage, please acknowledge
126** that you are using a library derived from SOFA, rather than SOFA
127** itself.
128**
129**
130** TERMS AND CONDITIONS
131**
132** Redistribution and use in source and binary forms, with or without
133** modification, are permitted provided that the following conditions
134** are met:
135**
136** 1 Redistributions of source code must retain the above copyright
137** notice, this list of conditions and the following disclaimer.
138**
139** 2 Redistributions in binary form must reproduce the above copyright
140** notice, this list of conditions and the following disclaimer in
141** the documentation and/or other materials provided with the
142** distribution.
143**
144** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
145** the International Astronomical Union nor the names of its
146** contributors may be used to endorse or promote products derived
147** from this software without specific prior written permission.
148**
149** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
150** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
151** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
152** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
153** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
154** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
155** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
156** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
157** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
158** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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160** POSSIBILITY OF SUCH DAMAGE.
161**
162*/
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