1 #include "erfa.h"
2 #include "erfam.h"
3 
eraPr00(double date1,double date2,double * dpsipr,double * depspr)4 void eraPr00(double date1, double date2, double *dpsipr, double *depspr)
5 /*
6 **  - - - - - - - -
7 **   e r a P r 0 0
8 **  - - - - - - - -
9 **
10 **  Precession-rate part of the IAU 2000 precession-nutation models
11 **  (part of MHB2000).
12 **
13 **  Given:
14 **     date1,date2    double  TT as a 2-part Julian Date (Note 1)
15 **
16 **  Returned:
17 **     dpsipr,depspr  double  precession corrections (Notes 2,3)
18 **
19 **  Notes:
20 **
21 **  1) The TT date date1+date2 is a Julian Date, apportioned in any
22 **     convenient way between the two arguments.  For example,
23 **     JD(TT)=2450123.7 could be expressed in any of these ways,
24 **     among others:
25 **
26 **            date1          date2
27 **
28 **         2450123.7           0.0       (JD method)
29 **         2451545.0       -1421.3       (J2000 method)
30 **         2400000.5       50123.2       (MJD method)
31 **         2450123.5           0.2       (date & time method)
32 **
33 **     The JD method is the most natural and convenient to use in
34 **     cases where the loss of several decimal digits of resolution
35 **     is acceptable.  The J2000 method is best matched to the way
36 **     the argument is handled internally and will deliver the
37 **     optimum resolution.  The MJD method and the date & time methods
38 **     are both good compromises between resolution and convenience.
39 **
40 **  2) The precession adjustments are expressed as "nutation
41 **     components", corrections in longitude and obliquity with respect
42 **     to the J2000.0 equinox and ecliptic.
43 **
44 **  3) Although the precession adjustments are stated to be with respect
45 **     to Lieske et al. (1977), the MHB2000 model does not specify which
46 **     set of Euler angles are to be used and how the adjustments are to
47 **     be applied.  The most literal and straightforward procedure is to
48 **     adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and
49 **     to add dpsipr to psi_A and depspr to both omega_A and eps_A.
50 **
51 **  4) This is an implementation of one aspect of the IAU 2000A nutation
52 **     model, formally adopted by the IAU General Assembly in 2000,
53 **     namely MHB2000 (Mathews et al. 2002).
54 **
55 **  References:
56 **
57 **     Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions
58 **     for the precession quantities based upon the IAU (1976) System of
59 **     Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977)
60 **
61 **     Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation
62 **     and precession   New nutation series for nonrigid Earth and
63 **     insights into the Earth's interior", J.Geophys.Res., 107, B4,
64 **     2002.  The MHB2000 code itself was obtained on 9th September 2002
65 **     from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.
66 **
67 **     Wallace, P.T., "Software for Implementing the IAU 2000
68 **     Resolutions", in IERS Workshop 5.1 (2002).
69 **
70 **  This revision:  2021 May 11
71 **
72 **  Copyright (C) 2013-2021, NumFOCUS Foundation.
73 **  Derived, with permission, from the SOFA library.  See notes at end of file.
74 */
75 {
76    double t;
77 
78 /* Precession and obliquity corrections (radians per century) */
79    static const double PRECOR = -0.29965 * ERFA_DAS2R,
80                        OBLCOR = -0.02524 * ERFA_DAS2R;
81 
82 
83 /* Interval between fundamental epoch J2000.0 and given date (JC). */
84    t = ((date1 - ERFA_DJ00) + date2) / ERFA_DJC;
85 
86 /* Precession rate contributions with respect to IAU 1976/80. */
87    *dpsipr = PRECOR * t;
88    *depspr = OBLCOR * t;
89 
90 /* Finished. */
91 
92 }
93 /*----------------------------------------------------------------------
94 **
95 **
96 **  Copyright (C) 2013-2021, NumFOCUS Foundation.
97 **  All rights reserved.
98 **
99 **  This library is derived, with permission, from the International
100 **  Astronomical Union's "Standards of Fundamental Astronomy" library,
101 **  available from http://www.iausofa.org.
102 **
103 **  The ERFA version is intended to retain identical functionality to
104 **  the SOFA library, but made distinct through different function and
105 **  file names, as set out in the SOFA license conditions.  The SOFA
106 **  original has a role as a reference standard for the IAU and IERS,
107 **  and consequently redistribution is permitted only in its unaltered
108 **  state.  The ERFA version is not subject to this restriction and
109 **  therefore can be included in distributions which do not support the
110 **  concept of "read only" software.
111 **
112 **  Although the intent is to replicate the SOFA API (other than
113 **  replacement of prefix names) and results (with the exception of
114 **  bugs;  any that are discovered will be fixed), SOFA is not
115 **  responsible for any errors found in this version of the library.
116 **
117 **  If you wish to acknowledge the SOFA heritage, please acknowledge
118 **  that you are using a library derived from SOFA, rather than SOFA
119 **  itself.
120 **
121 **
122 **  TERMS AND CONDITIONS
123 **
124 **  Redistribution and use in source and binary forms, with or without
125 **  modification, are permitted provided that the following conditions
126 **  are met:
127 **
128 **  1 Redistributions of source code must retain the above copyright
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130 **
131 **  2 Redistributions in binary form must reproduce the above copyright
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133 **    the documentation and/or other materials provided with the
134 **    distribution.
135 **
136 **  3 Neither the name of the Standards Of Fundamental Astronomy Board,
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155