1 /* 2 3 -Procedure tyear_c ( Seconds per tropical year ) 4 5 -Abstract 6 7 Return the number of seconds in a tropical year. 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 tyear_c(void)46 SpiceDouble tyear_c ( void ) 47 48 /* 49 50 -Brief_I/O 51 52 VARIABLE I/O DESCRIPTION 53 -------- --- -------------------------------------------------- 54 tyear_c O The number of seconds/tropical year 55 56 -Detailed_Input 57 58 None. 59 60 -Detailed_Output 61 62 The function returns the number of seconds per tropical 63 year. This value is taken from the 1992 Explanatory Supplement 64 to the Astronomical Almanac. 65 66 -Parameters 67 68 None. 69 70 -Particulars 71 72 The tropical year is often used as a fundamental unit 73 of time when dealing with older ephemeris data. For this 74 reason its value in terms of ephemeris seconds is 75 recorded in this function. 76 77 -Examples 78 79 Suppose you wish to compute the number of tropical centuries 80 that have elapsed since the ephemeris epoch B1950 (beginning 81 of the Besselian year 1950) at a particular ET epoch. The 82 following line of code will do the trick. 83 84 85 century = ( et - unitim_ ( b1950_c(), "JED", "ET" ) ) 86 / ( 100.0 * tyear_c() ); 87 88 89 -Restrictions 90 91 None. 92 93 -Exceptions 94 95 Error free. 96 97 -Files 98 99 None. 100 101 -Author_and_Institution 102 103 W.L. Taber (JPL) 104 E.D. Wright (JPL) 105 106 -Literature_References 107 108 Explanatory Supplement to the Astronomical Almanac. 109 Page 80. University Science Books, 20 Edgehill Road, 110 Mill Valley, CA 94941 111 112 -Version 113 114 -CSPICE Version 1.0.0, 08-FEB-1998 (EDW) 115 116 -Index_Entries 117 118 Number of seconds per tropical year 119 120 -& 121 */ 122 123 { /* Begin tyear_c */ 124 125 return 31556925.9747; 126 127 } /* End tyear_c */ 128