source: trunk/FACT++/erfa/src/atio13.c

Last change on this file was 18921, checked in by tbretz, 7 years ago
Updated to ERFA 1.4.0
File size: 9.8 KB
Line 
1#include "erfa.h"
2
3int eraAtio13(double ri, double di,
4 double utc1, double utc2, double dut1,
5 double elong, double phi, double hm, double xp, double yp,
6 double phpa, double tc, double rh, double wl,
7 double *aob, double *zob, double *hob,
8 double *dob, double *rob)
9/*
10** - - - - - - - - - -
11** e r a A t i o 1 3
12** - - - - - - - - - -
13**
14** CIRS RA,Dec to observed place. The caller supplies UTC, site
15** coordinates, ambient air conditions and observing wavelength.
16**
17** Given:
18** ri double CIRS right ascension (CIO-based, radians)
19** di double CIRS declination (radians)
20** utc1 double UTC as a 2-part...
21** utc2 double ...quasi Julian Date (Notes 1,2)
22** dut1 double UT1-UTC (seconds, Note 3)
23** elong double longitude (radians, east +ve, Note 4)
24** phi double geodetic latitude (radians, Note 4)
25** hm double height above ellipsoid (m, geodetic Notes 4,6)
26** xp,yp double polar motion coordinates (radians, Note 5)
27** phpa double pressure at the observer (hPa = mB, Note 6)
28** tc double ambient temperature at the observer (deg C)
29** rh double relative humidity at the observer (range 0-1)
30** wl double wavelength (micrometers, Note 7)
31**
32** Returned:
33** aob double* observed azimuth (radians: N=0,E=90)
34** zob double* observed zenith distance (radians)
35** hob double* observed hour angle (radians)
36** dob double* observed declination (radians)
37** rob double* observed right ascension (CIO-based, radians)
38**
39** Returned (function value):
40** int status: +1 = dubious year (Note 2)
41** 0 = OK
42** -1 = unacceptable date
43**
44** Notes:
45**
46** 1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
47** convenient way between the two arguments, for example where utc1
48** is the Julian Day Number and utc2 is the fraction of a day.
49**
50** However, JD cannot unambiguously represent UTC during a leap
51** second unless special measures are taken. The convention in the
52** present function is that the JD day represents UTC days whether
53** the length is 86399, 86400 or 86401 SI seconds.
54**
55** Applications should use the function eraDtf2d to convert from
56** calendar date and time of day into 2-part quasi Julian Date, as
57** it implements the leap-second-ambiguity convention just
58** described.
59**
60** 2) The warning status "dubious year" flags UTCs that predate the
61** introduction of the time scale or that are too far in the
62** future to be trusted. See eraDat for further details.
63**
64** 3) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
65** one second at the end of each positive UTC leap second,
66** introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
67** practice is under review, and in the future UT1-UTC may grow
68** essentially without limit.
69**
70** 4) The geographical coordinates are with respect to the ERFA_WGS84
71** reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
72** longitude required by the present function is east-positive
73** (i.e. right-handed), in accordance with geographical convention.
74**
75** 5) The polar motion xp,yp can be obtained from IERS bulletins. The
76** values are the coordinates (in radians) of the Celestial
77** Intermediate Pole with respect to the International Terrestrial
78** Reference System (see IERS Conventions 2003), measured along the
79** meridians 0 and 90 deg west respectively. For many
80** applications, xp and yp can be set to zero.
81**
82** 6) If hm, the height above the ellipsoid of the observing station
83** in meters, is not known but phpa, the pressure in hPa (=mB), is
84** available, an adequate estimate of hm can be obtained from the
85** expression
86**
87** hm = -29.3 * tsl * log ( phpa / 1013.25 );
88**
89** where tsl is the approximate sea-level air temperature in K
90** (See Astrophysical Quantities, C.W.Allen, 3rd edition, section
91** 52). Similarly, if the pressure phpa is not known, it can be
92** estimated from the height of the observing station, hm, as
93** follows:
94**
95** phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
96**
97** Note, however, that the refraction is nearly proportional to
98** the pressure and that an accurate phpa value is important for
99** precise work.
100**
101** 7) The argument wl specifies the observing wavelength in
102** micrometers. The transition from optical to radio is assumed to
103** occur at 100 micrometers (about 3000 GHz).
104**
105** 8) "Observed" Az,ZD means the position that would be seen by a
106** perfect geodetically aligned theodolite. (Zenith distance is
107** used rather than altitude in order to reflect the fact that no
108** allowance is made for depression of the horizon.) This is
109** related to the observed HA,Dec via the standard rotation, using
110** the geodetic latitude (corrected for polar motion), while the
111** observed HA and RA are related simply through the Earth rotation
112** angle and the site longitude. "Observed" RA,Dec or HA,Dec thus
113** means the position that would be seen by a perfect equatorial
114** with its polar axis aligned to the Earth's axis of rotation.
115**
116** 9) The accuracy of the result is limited by the corrections for
117** refraction, which use a simple A*tan(z) + B*tan^3(z) model.
118** Providing the meteorological parameters are known accurately and
119** there are no gross local effects, the predicted astrometric
120** coordinates should be within 0.05 arcsec (optical) or 1 arcsec
121** (radio) for a zenith distance of less than 70 degrees, better
122** than 30 arcsec (optical or radio) at 85 degrees and better
123** than 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
124**
125** 10) The complementary functions eraAtio13 and eraAtoi13 are self-
126** consistent to better than 1 microarcsecond all over the
127** celestial sphere.
128**
129** 11) It is advisable to take great care with units, as even unlikely
130** values of the input parameters are accepted and processed in
131** accordance with the models used.
132**
133** Called:
134** eraApio13 astrometry parameters, CIRS-observed, 2013
135** eraAtioq quick CIRS to observed
136**
137** Copyright (C) 2013-2017, NumFOCUS Foundation.
138** Derived, with permission, from the SOFA library. See notes at end of file.
139*/
140{
141 int j;
142 eraASTROM astrom;
143
144
145/* Star-independent astrometry parameters for CIRS->observed. */
146 j = eraApio13(utc1, utc2, dut1, elong, phi, hm, xp, yp,
147 phpa, tc, rh, wl, &astrom);
148
149/* Abort if bad UTC. */
150 if ( j < 0 ) return j;
151
152/* Transform CIRS to observed. */
153 eraAtioq(ri, di, &astrom, aob, zob, hob, dob, rob);
154
155/* Return OK/warning status. */
156 return j;
157
158/* Finished. */
159
160}
161/*----------------------------------------------------------------------
162**
163**
164** Copyright (C) 2013-2017, NumFOCUS Foundation.
165** All rights reserved.
166**
167** This library is derived, with permission, from the International
168** Astronomical Union's "Standards of Fundamental Astronomy" library,
169** available from http://www.iausofa.org.
170**
171** The ERFA version is intended to retain identical functionality to
172** the SOFA library, but made distinct through different function and
173** file names, as set out in the SOFA license conditions. The SOFA
174** original has a role as a reference standard for the IAU and IERS,
175** and consequently redistribution is permitted only in its unaltered
176** state. The ERFA version is not subject to this restriction and
177** therefore can be included in distributions which do not support the
178** concept of "read only" software.
179**
180** Although the intent is to replicate the SOFA API (other than
181** replacement of prefix names) and results (with the exception of
182** bugs; any that are discovered will be fixed), SOFA is not
183** responsible for any errors found in this version of the library.
184**
185** If you wish to acknowledge the SOFA heritage, please acknowledge
186** that you are using a library derived from SOFA, rather than SOFA
187** itself.
188**
189**
190** TERMS AND CONDITIONS
191**
192** Redistribution and use in source and binary forms, with or without
193** modification, are permitted provided that the following conditions
194** are met:
195**
196** 1 Redistributions of source code must retain the above copyright
197** notice, this list of conditions and the following disclaimer.
198**
199** 2 Redistributions in binary form must reproduce the above copyright
200** notice, this list of conditions and the following disclaimer in
201** the documentation and/or other materials provided with the
202** distribution.
203**
204** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
205** the International Astronomical Union nor the names of its
206** contributors may be used to endorse or promote products derived
207** from this software without specific prior written permission.
208**
209** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
210** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
211** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
212** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
213** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
214** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
215** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
216** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
217** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
218** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
219** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
220** POSSIBILITY OF SUCH DAMAGE.
221**
222*/
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