1 /* recrad.f -- translated by f2c (version 19980913).
2 You must link the resulting object file with the libraries:
3 -lf2c -lm (in that order)
4 */
5
6 #include "f2c.h"
7
8 /* $Procedure RECRAD ( Rectangular coordinates to RA and DEC ) */
recrad_(doublereal * rectan,doublereal * range,doublereal * ra,doublereal * dec)9 /* Subroutine */ int recrad_(doublereal *rectan, doublereal *range,
10 doublereal *ra, doublereal *dec)
11 {
12 extern doublereal twopi_(void);
13 extern /* Subroutine */ int reclat_(doublereal *, doublereal *,
14 doublereal *, doublereal *);
15
16 /* $ Abstract */
17
18 /* Convert rectangular coordinates to range, right ascension, */
19 /* and declination. */
20
21 /* $ Disclaimer */
22
23 /* THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
24 /* CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
25 /* GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
26 /* ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
27 /* PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
28 /* TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
29 /* WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
30 /* PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
31 /* SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
32 /* SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */
33
34 /* IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
35 /* BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
36 /* LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
37 /* INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
38 /* REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
39 /* REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */
40
41 /* RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
42 /* THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
43 /* CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
44 /* ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */
45
46 /* $ Required_Reading */
47
48 /* None. */
49
50 /* $ Keywords */
51
52 /* CONVERSION, COORDINATES */
53
54 /* $ Declarations */
55 /* $ Brief_I/O */
56
57 /* VARIABLE I/O DESCRIPTION */
58 /* -------- --- -------------------------------------------------- */
59 /* RECTAN I Rectangular coordinates of a point. */
60 /* RANGE O Distance of the point from the origin. */
61 /* RA O Right ascension in radians. */
62 /* DEC O Declination in radians. */
63
64 /* $ Detailed_Input */
65
66 /* RECTAN The rectangular coordinates of a point. */
67
68 /* $ Detailed_Output */
69
70 /* RANGE is the distance of the point from the origin. */
71
72 /* The units associated with RANGE are those */
73 /* associated with the input RECTAN. */
74
75
76 /* RA is the right ascension of RECTAN. This is the angular */
77 /* distance measured toward the east from the prime */
78 /* meridian to the meridian containing the input point. */
79 /* The direction of increasing right ascension is from */
80 /* the +X axis towards the +Y axis. */
81
82 /* RA is output in radians. The range of RA is [0, 2*pi]. */
83
84
85 /* DEC is the declination of RECTAN. This is the angle from */
86 /* the XY plane of the ray from the origin through the */
87 /* point. */
88
89 /* DEC is output in radians. The range of DEC is */
90 /* [-pi/2, pi/2]. */
91
92 /* $ Parameters */
93
94 /* None. */
95
96 /* $ Exceptions */
97
98 /* Error free. */
99
100 /* 1) If the X and Y components of RECTAN are both zero, the */
101 /* right ascension is set to zero. */
102
103 /* 2) If RECTAN is the zero vector, right ascension and declination */
104 /* are both set to zero. */
105
106 /* $ Files */
107
108 /* None. */
109
110 /* $ Particulars */
111
112 /* This routine returns the range, right ascension, and declination */
113 /* of a point specified in rectangular coordinates. */
114
115 /* The output is defined by a distance from a central reference */
116 /* point, an angle from a reference meridian, and an angle above */
117 /* the equator of a sphere centered at the central reference */
118 /* point. */
119
120 /* $ Examples */
121
122 /* The following code fragment converts right ascension and */
123 /* declination from the B1950 reference frame to the J2000 frame. */
124
125 /* C */
126 /* C Convert RA and DEC to a 3-vector expressed in */
127 /* C the B1950 frame. */
128 /* C */
129 /* CALL RADREC ( 1.D0, RA, DEC, V1950 ) */
130 /* C */
131 /* C We use the SPICELIB routine PXFORM to obtain the */
132 /* C transformation matrix for converting vectors between */
133 /* C the B1950 and J2000 reference frames. Since */
134 /* C both frames are inertial, the input time value we */
135 /* C supply to PXFORM is arbitrary. We choose zero */
136 /* C seconds past the J2000 epoch. */
137 /* C */
138 /* CALL PXFORM ( 'B1950', 'J2000', 0.D0, MTRANS ) */
139 /* C */
140 /* C Transform the vector to the J2000 frame. */
141 /* C */
142 /* CALL MXV ( MTRANS, V1950, V2000 ) */
143 /* C */
144 /* C Find the RA and DEC of the J2000-relative vector. */
145 /* C */
146 /* CALL RECRAD ( V2000, R, RA, DEC ) */
147
148
149 /* $ Restrictions */
150
151 /* None. */
152
153 /* $ Author_and_Institution */
154
155 /* C.H. Acton (JPL) */
156 /* N.J. Bachman (JPL) */
157 /* H.A. Neilan (JPL) */
158
159 /* $ Literature_References */
160
161 /* None. */
162
163 /* $ Version */
164
165 /* - SPICELIB Version 1.0.2, 30-JUL-2003 (NJB) (CHA) */
166
167 /* Various header changes were made to improve clarity. Some */
168 /* minor header corrections were made. */
169
170 /* - SPICELIB Version 1.0.1, 10-MAR-1992 (WLT) */
171
172 /* Comment section for permuted index source lines was added */
173 /* following the header. */
174
175 /* - SPICELIB Version 1.0.0, 31-JAN-1990 (HAN) */
176
177 /* -& */
178 /* $ Index_Entries */
179
180 /* rectangular coordinates to ra and dec */
181 /* rectangular to right_ascension and declination */
182
183 /* -& */
184
185 /* SPICELIB functions */
186
187
188 /* Call the subroutine RECLAT to convert the rectangular coordinates */
189 /* into latitudinal coordinates. In RECLAT, the longitude ( which */
190 /* is returned to this subroutine as RA ) ranges from - pi to pi */
191 /* radians. Because the right ascension ranges from zero to */
192 /* two pi radians, whenever RA is negative two pi must be added to */
193 /* it. */
194
195 reclat_(rectan, range, ra, dec);
196 if (*ra < 0.) {
197 *ra += twopi_();
198 }
199 return 0;
200 } /* recrad_ */
201
202