source: branches/FACT++_part_filenames/erfa/src/pmsafe.c@ 20115

Last change on this file since 20115 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: 8.6 KB
Line 
1#include "erfa.h"
2
3int eraPmsafe(double ra1, double dec1, double pmr1, double pmd1,
4 double px1, double rv1,
5 double ep1a, double ep1b, double ep2a, double ep2b,
6 double *ra2, double *dec2, double *pmr2, double *pmd2,
7 double *px2, double *rv2)
8/*
9** - - - - - - - - - -
10** e r a P m s a f e
11** - - - - - - - - - -
12**
13** Star proper motion: update star catalog data for space motion, with
14** special handling to handle the zero parallax case.
15**
16** Given:
17** ra1 double right ascension (radians), before
18** dec1 double declination (radians), before
19** pmr1 double RA proper motion (radians/year), before
20** pmd1 double Dec proper motion (radians/year), before
21** px1 double parallax (arcseconds), before
22** rv1 double radial velocity (km/s, +ve = receding), before
23** ep1a double "before" epoch, part A (Note 1)
24** ep1b double "before" epoch, part B (Note 1)
25** ep2a double "after" epoch, part A (Note 1)
26** ep2b double "after" epoch, part B (Note 1)
27**
28** Returned:
29** ra2 double right ascension (radians), after
30** dec2 double declination (radians), after
31** pmr2 double RA proper motion (radians/year), after
32** pmd2 double Dec proper motion (radians/year), after
33** px2 double parallax (arcseconds), after
34** rv2 double radial velocity (km/s, +ve = receding), after
35**
36** Returned (function value):
37** int status:
38** -1 = system error (should not occur)
39** 0 = no warnings or errors
40** 1 = distance overridden (Note 6)
41** 2 = excessive velocity (Note 7)
42** 4 = solution didn't converge (Note 8)
43** else = binary logical OR of the above warnings
44**
45** Notes:
46**
47** 1) The starting and ending TDB epochs ep1a+ep1b and ep2a+ep2b are
48** Julian Dates, apportioned in any convenient way between the two
49** parts (A and B). For example, JD(TDB)=2450123.7 could be
50** expressed in any of these ways, among others:
51**
52** epNa epNb
53**
54** 2450123.7 0.0 (JD method)
55** 2451545.0 -1421.3 (J2000 method)
56** 2400000.5 50123.2 (MJD method)
57** 2450123.5 0.2 (date & time method)
58**
59** The JD method is the most natural and convenient to use in cases
60** where the loss of several decimal digits of resolution is
61** acceptable. The J2000 method is best matched to the way the
62** argument is handled internally and will deliver the optimum
63** resolution. The MJD method and the date & time methods are both
64** good compromises between resolution and convenience.
65**
66** 2) In accordance with normal star-catalog conventions, the object's
67** right ascension and declination are freed from the effects of
68** secular aberration. The frame, which is aligned to the catalog
69** equator and equinox, is Lorentzian and centered on the SSB.
70**
71** The proper motions are the rate of change of the right ascension
72** and declination at the catalog epoch and are in radians per TDB
73** Julian year.
74**
75** The parallax and radial velocity are in the same frame.
76**
77** 3) Care is needed with units. The star coordinates are in radians
78** and the proper motions in radians per Julian year, but the
79** parallax is in arcseconds.
80**
81** 4) The RA proper motion is in terms of coordinate angle, not true
82** angle. If the catalog uses arcseconds for both RA and Dec proper
83** motions, the RA proper motion will need to be divided by cos(Dec)
84** before use.
85**
86** 5) Straight-line motion at constant speed, in the inertial frame, is
87** assumed.
88**
89** 6) An extremely small (or zero or negative) parallax is overridden
90** to ensure that the object is at a finite but very large distance,
91** but not so large that the proper motion is equivalent to a large
92** but safe speed (about 0.1c using the chosen constant). A warning
93** status of 1 is added to the status if this action has been taken.
94**
95** 7) If the space velocity is a significant fraction of c (see the
96** constant VMAX in the function eraStarpv), it is arbitrarily set
97** to zero. When this action occurs, 2 is added to the status.
98**
99** 8) The relativistic adjustment carried out in the eraStarpv function
100** involves an iterative calculation. If the process fails to
101** converge within a set number of iterations, 4 is added to the
102** status.
103**
104** Called:
105** eraSeps angle between two points
106** eraStarpm update star catalog data for space motion
107**
108** Copyright (C) 2013-2016, NumFOCUS Foundation.
109** Derived, with permission, from the SOFA library. See notes at end of file.
110*/
111{
112
113/* Minimum allowed parallax (arcsec) */
114 const double PXMIN = 5e-7;
115
116/* Factor giving maximum allowed transverse speed of about 1% c */
117 const double F = 326.0;
118
119 int jpx, j;
120 double pm, px1a;
121
122
123/* Proper motion in one year (radians). */
124 pm = eraSeps(ra1, dec1, ra1+pmr1, dec1+pmd1);
125
126/* Override the parallax to reduce the chances of a warning status. */
127 jpx = 0;
128 px1a = px1;
129 pm *= F;
130 if (px1a < pm) {jpx = 1; px1a = pm;}
131 if (px1a < PXMIN) {jpx = 1; px1a = PXMIN;}
132
133/* Carry out the transformation using the modified parallax. */
134 j = eraStarpm(ra1, dec1, pmr1, pmd1, px1a, rv1,
135 ep1a, ep1b, ep2a, ep2b,
136 ra2, dec2, pmr2, pmd2, px2, rv2);
137
138/* Revise and return the status. */
139 if ( !(j%2) ) j += jpx;
140 return j;
141
142/* Finished. */
143
144}
145/*----------------------------------------------------------------------
146**
147**
148** Copyright (C) 2013-2016, NumFOCUS Foundation.
149** All rights reserved.
150**
151** This library is derived, with permission, from the International
152** Astronomical Union's "Standards of Fundamental Astronomy" library,
153** available from http://www.iausofa.org.
154**
155** The ERFA version is intended to retain identical functionality to
156** the SOFA library, but made distinct through different function and
157** file names, as set out in the SOFA license conditions. The SOFA
158** original has a role as a reference standard for the IAU and IERS,
159** and consequently redistribution is permitted only in its unaltered
160** state. The ERFA version is not subject to this restriction and
161** therefore can be included in distributions which do not support the
162** concept of "read only" software.
163**
164** Although the intent is to replicate the SOFA API (other than
165** replacement of prefix names) and results (with the exception of
166** bugs; any that are discovered will be fixed), SOFA is not
167** responsible for any errors found in this version of the library.
168**
169** If you wish to acknowledge the SOFA heritage, please acknowledge
170** that you are using a library derived from SOFA, rather than SOFA
171** itself.
172**
173**
174** TERMS AND CONDITIONS
175**
176** Redistribution and use in source and binary forms, with or without
177** modification, are permitted provided that the following conditions
178** are met:
179**
180** 1 Redistributions of source code must retain the above copyright
181** notice, this list of conditions and the following disclaimer.
182**
183** 2 Redistributions in binary form must reproduce the above copyright
184** notice, this list of conditions and the following disclaimer in
185** the documentation and/or other materials provided with the
186** distribution.
187**
188** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
189** the International Astronomical Union nor the names of its
190** contributors may be used to endorse or promote products derived
191** from this software without specific prior written permission.
192**
193** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
194** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
195** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
196** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
197** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
198** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
199** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
200** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
201** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
202** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
203** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
204** POSSIBILITY OF SUCH DAMAGE.
205**
206*/
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