source: branches/FACT++_lidctrl_usb/erfa/src/starpm.c@ 19675

Last change on this file since 19675 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: 9.0 KB
Line 
1#include "erfa.h"
2
3int eraStarpm(double ra1, double dec1,
4 double pmr1, double pmd1, double px1, double rv1,
5 double ep1a, double ep1b, double ep2a, double ep2b,
6 double *ra2, double *dec2,
7 double *pmr2, double *pmd2, double *px2, double *rv2)
8/*
9** - - - - - - - - - -
10** e r a S t a r p m
11** - - - - - - - - - -
12**
13** Star proper motion: update star catalog data for space motion.
14**
15** Given:
16** ra1 double right ascension (radians), before
17** dec1 double declination (radians), before
18** pmr1 double RA proper motion (radians/year), before
19** pmd1 double Dec proper motion (radians/year), before
20** px1 double parallax (arcseconds), before
21** rv1 double radial velocity (km/s, +ve = receding), before
22** ep1a double "before" epoch, part A (Note 1)
23** ep1b double "before" epoch, part B (Note 1)
24** ep2a double "after" epoch, part A (Note 1)
25** ep2b double "after" epoch, part B (Note 1)
26**
27** Returned:
28** ra2 double right ascension (radians), after
29** dec2 double declination (radians), after
30** pmr2 double RA proper motion (radians/year), after
31** pmd2 double Dec proper motion (radians/year), after
32** px2 double parallax (arcseconds), after
33** rv2 double radial velocity (km/s, +ve = receding), after
34**
35** Returned (function value):
36** int status:
37** -1 = system error (should not occur)
38** 0 = no warnings or errors
39** 1 = distance overridden (Note 6)
40** 2 = excessive velocity (Note 7)
41** 4 = solution didn't converge (Note 8)
42** else = binary logical OR of the above warnings
43**
44** Notes:
45**
46** 1) The starting and ending TDB dates ep1a+ep1b and ep2a+ep2b are
47** Julian Dates, apportioned in any convenient way between the two
48** parts (A and B). For example, JD(TDB)=2450123.7 could be
49** expressed in any of these ways, among others:
50**
51** epna epnb
52**
53** 2450123.7 0.0 (JD method)
54** 2451545.0 -1421.3 (J2000 method)
55** 2400000.5 50123.2 (MJD method)
56** 2450123.5 0.2 (date & time method)
57**
58** The JD method is the most natural and convenient to use in
59** cases where the loss of several decimal digits of resolution
60** is acceptable. The J2000 method is best matched to the way
61** the argument is handled internally and will deliver the
62** optimum resolution. The MJD method and the date & time methods
63** are both good compromises between resolution and convenience.
64**
65** 2) In accordance with normal star-catalog conventions, the object's
66** right ascension and declination are freed from the effects of
67** secular aberration. The frame, which is aligned to the catalog
68** equator and equinox, is Lorentzian and centered on the SSB.
69**
70** The proper motions are the rate of change of the right ascension
71** and declination at the catalog epoch and are in radians per TDB
72** Julian year.
73**
74** The parallax and radial velocity are in the same frame.
75**
76** 3) Care is needed with units. The star coordinates are in radians
77** and the proper motions in radians per Julian year, but the
78** parallax is in arcseconds.
79**
80** 4) The RA proper motion is in terms of coordinate angle, not true
81** angle. If the catalog uses arcseconds for both RA and Dec proper
82** motions, the RA proper motion will need to be divided by cos(Dec)
83** before use.
84**
85** 5) Straight-line motion at constant speed, in the inertial frame,
86** is assumed.
87**
88** 6) An extremely small (or zero or negative) parallax is interpreted
89** to mean that the object is on the "celestial sphere", the radius
90** of which is an arbitrary (large) value (see the eraStarpv
91** function for the value used). When the distance is overridden in
92** this way, the status, initially zero, has 1 added to it.
93**
94** 7) If the space velocity is a significant fraction of c (see the
95** constant VMAX in the function eraStarpv), it is arbitrarily set
96** to zero. When this action occurs, 2 is added to the status.
97**
98** 8) The relativistic adjustment carried out in the eraStarpv function
99** involves an iterative calculation. If the process fails to
100** converge within a set number of iterations, 4 is added to the
101** status.
102**
103** Called:
104** eraStarpv star catalog data to space motion pv-vector
105** eraPvu update a pv-vector
106** eraPdp scalar product of two p-vectors
107** eraPvstar space motion pv-vector to star catalog data
108**
109** Copyright (C) 2013-2016, NumFOCUS Foundation.
110** Derived, with permission, from the SOFA library. See notes at end of file.
111*/
112{
113 double pv1[2][3], tl1, dt, pv[2][3], r2, rdv, v2, c2mv2, tl2,
114 pv2[2][3];
115 int j1, j2, j;
116
117
118/* RA,Dec etc. at the "before" epoch to space motion pv-vector. */
119 j1 = eraStarpv(ra1, dec1, pmr1, pmd1, px1, rv1, pv1);
120
121/* Light time when observed (days). */
122 tl1 = eraPm(pv1[0]) / ERFA_DC;
123
124/* Time interval, "before" to "after" (days). */
125 dt = (ep2a - ep1a) + (ep2b - ep1b);
126
127/* Move star along track from the "before" observed position to the */
128/* "after" geometric position. */
129 eraPvu(dt + tl1, pv1, pv);
130
131/* From this geometric position, deduce the observed light time (days) */
132/* at the "after" epoch (with theoretically unneccessary error check). */
133 r2 = eraPdp(pv[0], pv[0]);
134 rdv = eraPdp(pv[0], pv[1]);
135 v2 = eraPdp(pv[1], pv[1]);
136 c2mv2 = ERFA_DC*ERFA_DC - v2;
137 if (c2mv2 <= 0) return -1;
138 tl2 = (-rdv + sqrt(rdv*rdv + c2mv2*r2)) / c2mv2;
139
140/* Move the position along track from the observed place at the */
141/* "before" epoch to the observed place at the "after" epoch. */
142 eraPvu(dt + (tl1 - tl2), pv1, pv2);
143
144/* Space motion pv-vector to RA,Dec etc. at the "after" epoch. */
145 j2 = eraPvstar(pv2, ra2, dec2, pmr2, pmd2, px2, rv2);
146
147/* Final status. */
148 j = (j2 == 0) ? j1 : -1;
149
150 return j;
151
152}
153/*----------------------------------------------------------------------
154**
155**
156** Copyright (C) 2013-2016, NumFOCUS Foundation.
157** All rights reserved.
158**
159** This library is derived, with permission, from the International
160** Astronomical Union's "Standards of Fundamental Astronomy" library,
161** available from http://www.iausofa.org.
162**
163** The ERFA version is intended to retain identical functionality to
164** the SOFA library, but made distinct through different function and
165** file names, as set out in the SOFA license conditions. The SOFA
166** original has a role as a reference standard for the IAU and IERS,
167** and consequently redistribution is permitted only in its unaltered
168** state. The ERFA version is not subject to this restriction and
169** therefore can be included in distributions which do not support the
170** concept of "read only" software.
171**
172** Although the intent is to replicate the SOFA API (other than
173** replacement of prefix names) and results (with the exception of
174** bugs; any that are discovered will be fixed), SOFA is not
175** responsible for any errors found in this version of the library.
176**
177** If you wish to acknowledge the SOFA heritage, please acknowledge
178** that you are using a library derived from SOFA, rather than SOFA
179** itself.
180**
181**
182** TERMS AND CONDITIONS
183**
184** Redistribution and use in source and binary forms, with or without
185** modification, are permitted provided that the following conditions
186** are met:
187**
188** 1 Redistributions of source code must retain the above copyright
189** notice, this list of conditions and the following disclaimer.
190**
191** 2 Redistributions in binary form must reproduce the above copyright
192** notice, this list of conditions and the following disclaimer in
193** the documentation and/or other materials provided with the
194** distribution.
195**
196** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
197** the International Astronomical Union nor the names of its
198** contributors may be used to endorse or promote products derived
199** from this software without specific prior written permission.
200**
201** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
202** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
203** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
204** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
205** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
206** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
207** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
208** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
209** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
210** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
211** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
212** POSSIBILITY OF SUCH DAMAGE.
213**
214*/
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