source: trunk/FACT++/erfa/src/pr00.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: 6.2 KB
Line 
1#include "erfa.h"
2
3void eraPr00(double date1, double date2, double *dpsipr, double *depspr)
4/*
5** - - - - - - - -
6** e r a P r 0 0
7** - - - - - - - -
8**
9** Precession-rate part of the IAU 2000 precession-nutation models
10** (part of MHB2000).
11**
12** Given:
13** date1,date2 double TT as a 2-part Julian Date (Note 1)
14**
15** Returned:
16** dpsipr,depspr double precession corrections (Notes 2,3)
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 precession adjustments are expressed as "nutation
40** components", corrections in longitude and obliquity with respect
41** to the J2000.0 equinox and ecliptic.
42**
43** 3) Although the precession adjustments are stated to be with respect
44** to Lieske et al. (1977), the MHB2000 model does not specify which
45** set of Euler angles are to be used and how the adjustments are to
46** be applied. The most literal and straightforward procedure is to
47** adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and
48** to add dpsipr to psi_A and depspr to both omega_A and eps_A.
49**
50** 4) This is an implementation of one aspect of the IAU 2000A nutation
51** model, formally adopted by the IAU General Assembly in 2000,
52** namely MHB2000 (Mathews et al. 2002).
53**
54** References:
55**
56** Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions
57** for the precession quantities based upon the IAU (1976) System of
58** Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977)
59**
60** Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
61** and precession New nutation series for nonrigid Earth and
62** insights into the Earth's interior", J.Geophys.Res., 107, B4,
63** 2002. The MHB2000 code itself was obtained on 9th September 2002
64** from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
65**
66** Wallace, P.T., "Software for Implementing the IAU 2000
67** Resolutions", in IERS Workshop 5.1 (2002).
68**
69** Copyright (C) 2013-2016, NumFOCUS Foundation.
70** Derived, with permission, from the SOFA library. See notes at end of file.
71*/
72{
73 double t;
74
75/* Precession and obliquity corrections (radians per century) */
76 static const double PRECOR = -0.29965 * ERFA_DAS2R,
77 OBLCOR = -0.02524 * ERFA_DAS2R;
78
79
80/* Interval between fundamental epoch J2000.0 and given date (JC). */
81 t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC;
82
83/* Precession rate contributions with respect to IAU 1976/80. */
84 *dpsipr = PRECOR * t;
85 *depspr = OBLCOR * t;
86
87 return;
88
89}
90/*----------------------------------------------------------------------
91**
92**
93** Copyright (C) 2013-2016, NumFOCUS Foundation.
94** All rights reserved.
95**
96** This library is derived, with permission, from the International
97** Astronomical Union's "Standards of Fundamental Astronomy" library,
98** available from http://www.iausofa.org.
99**
100** The ERFA version is intended to retain identical functionality to
101** the SOFA library, but made distinct through different function and
102** file names, as set out in the SOFA license conditions. The SOFA
103** original has a role as a reference standard for the IAU and IERS,
104** and consequently redistribution is permitted only in its unaltered
105** state. The ERFA version is not subject to this restriction and
106** therefore can be included in distributions which do not support the
107** concept of "read only" software.
108**
109** Although the intent is to replicate the SOFA API (other than
110** replacement of prefix names) and results (with the exception of
111** bugs; any that are discovered will be fixed), SOFA is not
112** responsible for any errors found in this version of the library.
113**
114** If you wish to acknowledge the SOFA heritage, please acknowledge
115** that you are using a library derived from SOFA, rather than SOFA
116** itself.
117**
118**
119** TERMS AND CONDITIONS
120**
121** Redistribution and use in source and binary forms, with or without
122** modification, are permitted provided that the following conditions
123** are met:
124**
125** 1 Redistributions of source code must retain the above copyright
126** notice, this list of conditions and the following disclaimer.
127**
128** 2 Redistributions in binary form must reproduce the above copyright
129** notice, this list of conditions and the following disclaimer in
130** the documentation and/or other materials provided with the
131** distribution.
132**
133** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
134** the International Astronomical Union nor the names of its
135** contributors may be used to endorse or promote products derived
136** from this software without specific prior written permission.
137**
138** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
139** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
140** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
141** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
142** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
143** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
144** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
145** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
146** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
147** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
148** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
149** POSSIBILITY OF SUCH DAMAGE.
150**
151*/
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