source: trunk/FACT++/sofa/src/nut06a.c@ 18375

Last change on this file since 18375 was 18346, checked in by tbretz, 11 years ago
File size: 7.6 KB
Line 
1#include "sofa.h"
2
3void iauNut06a(double date1, double date2, double *dpsi, double *deps)
4/*
5** - - - - - - - - - -
6** i a u 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** Status: canonical model.
19**
20** Notes:
21**
22** 1) The TT date date1+date2 is a Julian Date, apportioned in any
23** convenient way between the two arguments. For example,
24** JD(TT)=2450123.7 could be expressed in any of these ways,
25** among others:
26**
27** date1 date2
28**
29** 2450123.7 0.0 (JD method)
30** 2451545.0 -1421.3 (J2000 method)
31** 2400000.5 50123.2 (MJD method)
32** 2450123.5 0.2 (date & time method)
33**
34** The JD method is the most natural and convenient to use in
35** cases where the loss of several decimal digits of resolution
36** is acceptable. The J2000 method is best matched to the way
37** the argument is handled internally and will deliver the
38** optimum resolution. The MJD method and the date & time methods
39** are both good compromises between resolution and convenience.
40**
41** 2) The nutation components in longitude and obliquity are in radians
42** and with respect to the mean equinox and ecliptic of date,
43** IAU 2006 precession model (Hilton et al. 2006, Capitaine et al.
44** 2005).
45**
46** 3) The function first computes the IAU 2000A nutation, then applies
47** adjustments for (i) the consequences of the change in obliquity
48** from the IAU 1980 ecliptic to the IAU 2006 ecliptic and (ii) the
49** secular variation in the Earth's dynamical form factor J2.
50**
51** 4) The present function provides classical nutation, complementing
52** the IAU 2000 frame bias and IAU 2006 precession. It delivers a
53** pole which is at current epochs accurate to a few tens of
54** microarcseconds, apart from the free core nutation.
55**
56** Called:
57** iauNut00a nutation, IAU 2000A
58**
59** References:
60**
61** Chapront, J., Chapront-Touze, M. & Francou, G. 2002,
62** Astron.Astrophys. 387, 700
63**
64** Lieske, J.H., Lederle, T., Fricke, W. & Morando, B. 1977,
65** Astron.Astrophys. 58, 1-16
66**
67** Mathews, P.M., Herring, T.A., Buffet, B.A. 2002, J.Geophys.Res.
68** 107, B4. The MHB_2000 code itself was obtained on 9th September
69** 2002 from ftp//maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
70**
71** Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
72** Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683
73**
74** Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
75** Astron.Astrophys.Supp.Ser. 135, 111
76**
77** Wallace, P.T., "Software for Implementing the IAU 2000
78** Resolutions", in IERS Workshop 5.1 (2002)
79**
80** This revision: 2013 June 18
81**
82** SOFA release 2015-02-09
83**
84** Copyright (C) 2015 IAU SOFA Board. See notes at end.
85*/
86{
87 double t, fj2, dp, de;
88
89/* Interval between fundamental date J2000.0 and given date (JC). */
90 t = ((date1 - DJ00) + date2) / DJC;
91
92/* Factor correcting for secular variation of J2. */
93 fj2 = -2.7774e-6 * t;
94
95/* Obtain IAU 2000A nutation. */
96 iauNut00a(date1, date2, &dp, &de);
97
98/* Apply P03 adjustments (Wallace & Capitaine, 2006, Eqs.5). */
99 *dpsi = dp + dp * (0.4697e-6 + fj2);
100 *deps = de + de * fj2;
101
102 return;
103
104/*----------------------------------------------------------------------
105**
106** Copyright (C) 2015
107** Standards Of Fundamental Astronomy Board
108** of the International Astronomical Union.
109**
110** =====================
111** SOFA Software License
112** =====================
113**
114** NOTICE TO USER:
115**
116** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
117** CONDITIONS WHICH APPLY TO ITS USE.
118**
119** 1. The Software is owned by the IAU SOFA Board ("SOFA").
120**
121** 2. Permission is granted to anyone to use the SOFA software for any
122** purpose, including commercial applications, free of charge and
123** without payment of royalties, subject to the conditions and
124** restrictions listed below.
125**
126** 3. You (the user) may copy and distribute SOFA source code to others,
127** and use and adapt its code and algorithms in your own software,
128** on a world-wide, royalty-free basis. That portion of your
129** distribution that does not consist of intact and unchanged copies
130** of SOFA source code files is a "derived work" that must comply
131** with the following requirements:
132**
133** a) Your work shall be marked or carry a statement that it
134** (i) uses routines and computations derived by you from
135** software provided by SOFA under license to you; and
136** (ii) does not itself constitute software provided by and/or
137** endorsed by SOFA.
138**
139** b) The source code of your derived work must contain descriptions
140** of how the derived work is based upon, contains and/or differs
141** from the original SOFA software.
142**
143** c) The names of all routines in your derived work shall not
144** include the prefix "iau" or "sofa" or trivial modifications
145** thereof such as changes of case.
146**
147** d) The origin of the SOFA components of your derived work must
148** not be misrepresented; you must not claim that you wrote the
149** original software, nor file a patent application for SOFA
150** software or algorithms embedded in the SOFA software.
151**
152** e) These requirements must be reproduced intact in any source
153** distribution and shall apply to anyone to whom you have
154** granted a further right to modify the source code of your
155** derived work.
156**
157** Note that, as originally distributed, the SOFA software is
158** intended to be a definitive implementation of the IAU standards,
159** and consequently third-party modifications are discouraged. All
160** variations, no matter how minor, must be explicitly marked as
161** such, as explained above.
162**
163** 4. You shall not cause the SOFA software to be brought into
164** disrepute, either by misuse, or use for inappropriate tasks, or
165** by inappropriate modification.
166**
167** 5. The SOFA software is provided "as is" and SOFA makes no warranty
168** as to its use or performance. SOFA does not and cannot warrant
169** the performance or results which the user may obtain by using the
170** SOFA software. SOFA makes no warranties, express or implied, as
171** to non-infringement of third party rights, merchantability, or
172** fitness for any particular purpose. In no event will SOFA be
173** liable to the user for any consequential, incidental, or special
174** damages, including any lost profits or lost savings, even if a
175** SOFA representative has been advised of such damages, or for any
176** claim by any third party.
177**
178** 6. The provision of any version of the SOFA software under the terms
179** and conditions specified herein does not imply that future
180** versions will also be made available under the same terms and
181** conditions.
182*
183** In any published work or commercial product which uses the SOFA
184** software directly, acknowledgement (see www.iausofa.org) is
185** appreciated.
186**
187** Correspondence concerning SOFA software should be addressed as
188** follows:
189**
190** By email: sofa@ukho.gov.uk
191** By post: IAU SOFA Center
192** HM Nautical Almanac Office
193** UK Hydrographic Office
194** Admiralty Way, Taunton
195** Somerset, TA1 2DN
196** United Kingdom
197**
198**--------------------------------------------------------------------*/
199}
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