1 /*
2 
3 -Procedure  b1950_c ( Besselian Date 1950.0 )
4 
5 -Abstract
6 
7    Return the Julian Date corresponding to Besselian Date 1950.0.
8 
9 -Disclaimer
10 
11    THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE
12    CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S.
13    GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE
14    ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE
15    PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS"
16    TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY
17    WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A
18    PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC
19    SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE
20    SOFTWARE AND RELATED MATERIALS, HOWEVER USED.
21 
22    IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA
23    BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT
24    LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND,
25    INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS,
26    REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE
27    REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY.
28 
29    RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF
30    THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY
31    CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE
32    ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE.
33 
34 -Required_Reading
35 
36    None.
37 
38 -Keywords
39 
40    CONSTANTS
41 
42 */
43 
44    #include "SpiceUsr.h"
45 
b1950_c(void)46    SpiceDouble b1950_c ( void )
47 
48 /*
49 
50 -Brief_I/O
51 
52    The function returns the Julian Date corresponding to Besselian
53    date 1950.0.
54 
55 -Detailed_Input
56 
57    None.
58 
59 -Detailed_Output
60 
61    The function returns 2433282.42345905, the Julian Date corresponding
62    to Besselian Date 1950.0 as reported by Lieske [1].
63 
64 -Parameters
65 
66    None.
67 
68 -Exceptions
69 
70    Error free.
71 
72 -Files
73 
74    None.
75 
76 -Particulars
77 
78    Lieske [1] defines a mapping from Julian Ephemeris Date
79    to Besselian:
80 
81       BE = 1900. + (JED - 2415020.31352)/365.242198781
82 
83    The inverse mapping being:
84 
85       JED = (BE - 1900.)*365.242198781 + 2415020.31352
86 
87 -Examples
88 
89    The following code fragment illustrates the use of b1950_c.
90 
91         /.
92         Convert Julian Date to UTC seconds past the reference
93         epoch (b1950_c).
94         ./
95 
96         spref = ( jd - b1950_c() ) * spd_c();
97 
98 -Restrictions
99 
100    None.
101 
102 -Literature_References
103 
104    [1] Jay Lieske, ``Precession Matrix Based on IAU (1976)
105        System of Astronomical Constants,'' Astron. Astrophys.
106        73, 282-284 (1979).
107 
108 -Author_and_Institution
109 
110    W.L. Taber      (JPL)
111    I.M. Underwood  (JPL)
112 
113 -Version
114 
115    -CSPICE Version 2.0.0, 01-SEP-2005 (EDW)
116 
117       This routine now returns the value reported in the Lieske
118       paper:
119 
120          2433282.42345905
121 
122       The same value returned by the FORTRAN SPICELIB routine
123       B1950.
124 
125       This routine previously returned the value reported in the
126       "Explanatory Supplement to the Astronomical Almanac", 1992,
127       page 699:
128 
129          2433282.423
130 
131       The ESAA value describing a truncation of the Lieske value.
132       The difference between the two values expressed as seconds
133       yields approximately 39.662 seconds.
134 
135    -CSPICE Version 1.0.1, 08-FEB-1998 (EDW)
136 
137        Corrected and clarified header entries.
138 
139    -CSPICE Version 1.0.0, 25-OCT-1997 (EDW)
140 
141 -Index_Entries
142 
143    besselian date 1950.0
144 
145 -&
146 */
147 
148 { /* Begin b1950_c */
149 
150 
151    return 2433282.42345905;
152 
153 
154 } /* End b1950_c */
155