Procedure

     TYEAR ( Seconds per tropical year )

     DOUBLE PRECISION FUNCTION TYEAR ()

Abstract

     Return the number of seconds in a tropical year.

Required_Reading

     None.

Keywords

     CONSTANTS

Declarations

    None.

Brief_I/O

     The function returns the number of seconds per 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 (see [1]).

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.


        CENTRY = ( ET - UNITIM ( B1950(), 'JED', 'ET' ) )
       .       / ( 100.0D0 * TYEAR() )

Restrictions

     None.

Literature_References

     [1]  P. Kenneth Seidelmann (Ed.), "Explanatory Supplement to the
          Astronomical Almanac," p 80, University Science Books, 1992.

Author_and_Institution

     J. Diaz del Rio    (ODC Space)
     W.L. Taber         (JPL)

Version

    SPICELIB Version 1.0.1, 13-APR-2021 (JDR)

        Edited the header to comply with NAIF standard.

    SPICELIB Version 1.0.0, 13-JUL-1993 (WLT)