Procedure

   SpiceDouble tyear_c ( void ) 

Abstract

 
   Return the number of seconds in a tropical year. 
 

Required_Reading

 
None. 
 

Keywords

 
   CONSTANTS 
 

Brief_I/O

 
   VARIABLE  I/O              DESCRIPTION 
   --------  ---  -------------------------------------------------- 
   tyear_c       O   The number of seconds/tropical year 
 

Detailed_Input

 
   None. 
 

Detailed_Output

 
   The function returns the number of seconds per tropical 
   year.  This value is taken from the 1992 Explanatory Supplement 
   to the Astronomical Almanac. 
 

Parameters

 
   None. 
 

Exceptions

 
   Error free. 
 

Files

 
   None. 
 

Particulars

 
   The tropical year is often used as a fundamental unit 
   of time when dealing with older ephemeris data.  For this 
   reason its value in terms of ephemeris seconds is 
   recorded in this function. 
 

Examples

 
   Suppose you wish to compute the number of tropical centuries 
   that have elapsed since the ephemeris epoch B1950 (beginning 
   of the Besselian year 1950) at a particular ET epoch.  The 
   following line of code will do the trick. 
 
 
      century = ( et - unitim_ ( b1950_c(), "JED", "ET" ) ) 
                / ( 100.0 * tyear_c() );
 
 

Restrictions

 
    None. 
 

Literature_References

 
   Explanatory Supplement to the Astronomical Almanac. 
   Page 80. University Science Books, 20 Edgehill Road, 
   Mill Valley, CA 94941 
 

Author_and_Institution

 
   W.L. Taber      (JPL) 
   E.D. Wright     (JPL)
 

Version

   -CSPICE Version 1.0.0, 08-FEB-1998 (EDW)

Index_Entries

 
   Number of seconds per tropical year 
 

Link to routine tyear_c source file tyear_c.c