FACT++  1.0
aper.c
Go to the documentation of this file.
1 #include "erfa.h"
2 
3 void eraAper(double theta, eraASTROM *astrom)
4 /*
5 ** - - - - - - - -
6 ** e r a A p e r
7 ** - - - - - - - -
8 **
9 ** In the star-independent astrometry parameters, update only the
10 ** Earth rotation angle, supplied by the caller explicitly.
11 **
12 ** Given:
13 ** theta double Earth rotation angle (radians, Note 2)
14 ** astrom eraASTROM* star-independent astrometry parameters:
15 ** pmt double not used
16 ** eb double[3] not used
17 ** eh double[3] not used
18 ** em double not used
19 ** v double[3] not used
20 ** bm1 double not used
21 ** bpn double[3][3] not used
22 ** along double longitude + s' (radians)
23 ** xpl double not used
24 ** ypl double not used
25 ** sphi double not used
26 ** cphi double not used
27 ** diurab double not used
28 ** eral double not used
29 ** refa double not used
30 ** refb double not used
31 **
32 ** Returned:
33 ** astrom eraASTROM* star-independent astrometry parameters:
34 ** pmt double unchanged
35 ** eb double[3] unchanged
36 ** eh double[3] unchanged
37 ** em double unchanged
38 ** v double[3] unchanged
39 ** bm1 double unchanged
40 ** bpn double[3][3] unchanged
41 ** along double unchanged
42 ** xpl double unchanged
43 ** ypl double unchanged
44 ** sphi double unchanged
45 ** cphi double unchanged
46 ** diurab double unchanged
47 ** eral double "local" Earth rotation angle (radians)
48 ** refa double unchanged
49 ** refb double unchanged
50 **
51 ** Notes:
52 **
53 ** 1) This function exists to enable sidereal-tracking applications to
54 ** avoid wasteful recomputation of the bulk of the astrometry
55 ** parameters: only the Earth rotation is updated.
56 **
57 ** 2) For targets expressed as equinox based positions, such as
58 ** classical geocentric apparent (RA,Dec), the supplied theta can be
59 ** Greenwich apparent sidereal time rather than Earth rotation
60 ** angle.
61 **
62 ** 3) The function eraAper13 can be used instead of the present
63 ** function, and starts from UT1 rather than ERA itself.
64 **
65 ** 4) This is one of several functions that inserts into the astrom
66 ** structure star-independent parameters needed for the chain of
67 ** astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.
68 **
69 ** The various functions support different classes of observer and
70 ** portions of the transformation chain:
71 **
72 ** functions observer transformation
73 **
74 ** eraApcg eraApcg13 geocentric ICRS <-> GCRS
75 ** eraApci eraApci13 terrestrial ICRS <-> CIRS
76 ** eraApco eraApco13 terrestrial ICRS <-> observed
77 ** eraApcs eraApcs13 space ICRS <-> GCRS
78 ** eraAper eraAper13 terrestrial update Earth rotation
79 ** eraApio eraApio13 terrestrial CIRS <-> observed
80 **
81 ** Those with names ending in "13" use contemporary ERFA models to
82 ** compute the various ephemerides. The others accept ephemerides
83 ** supplied by the caller.
84 **
85 ** The transformation from ICRS to GCRS covers space motion,
86 ** parallax, light deflection, and aberration. From GCRS to CIRS
87 ** comprises frame bias and precession-nutation. From CIRS to
88 ** observed takes account of Earth rotation, polar motion, diurnal
89 ** aberration and parallax (unless subsumed into the ICRS <-> GCRS
90 ** transformation), and atmospheric refraction.
91 **
92 ** Copyright (C) 2013-2015, NumFOCUS Foundation.
93 ** Derived, with permission, from the SOFA library. See notes at end of file.
94 */
95 {
96  astrom->eral = theta + astrom->along;
97 
98 /* Finished. */
99 
100 }
101 /*----------------------------------------------------------------------
102 **
103 **
104 ** Copyright (C) 2013-2015, 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
159 ** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
160 ** POSSIBILITY OF SUCH DAMAGE.
161 **
162 */
eraAper
void eraAper(double theta, eraASTROM *astrom)
Definition: aper.c:3
eraASTROM::eral
double eral
Definition: erfam.h:31
eraASTROM::along
double along
Definition: erfam.h:24