source: branches/FACT++_lidctrl_usb/erfa/src/pr00.c@ 19875

Last change on this file since 19875 was 18711, checked in by tbretz, 10 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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