Index of Functions: A B C D E F G H I J K L M N O P Q R S T U V W X
Index Page jyear_c

Table of contents

Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

       jyear_c ( Seconds per julian year )

       SpiceDouble jyear_c ( void )

#### Abstract

       Return the number of seconds in a julian year.

#### Required_Reading

       None.

#### Keywords

       CONSTANTS

#### Brief_I/O

       The function returns the number of seconds per julian year.

#### Detailed_Input

       None.

#### Detailed_Output

       The function returns the number of seconds per julian year.

#### Parameters

       None.

#### Exceptions

       Error free.

#### Files

       None.

#### Particulars

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

#### Examples

       The numerical results shown for these examples may differ across
       platforms. The results depend on the SPICE kernels used as
       input, the compiler and supporting libraries, and the machine
       specific arithmetic implementation.

       1) Display the number of seconds in a Julian year.

          Example code begins here.

          /.
             Program jyear_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {
             /.
             Display the number of seconds in a Julian Year, in 16.3 floating
             point format
             ./
             printf ( "Seconds per Julian year: %16.3f\n", jyear_c() );

             return ( 0 );
          }

          When this program was executed on a Mac/Intel/cc/64-bit
          platform, the output was:

          Seconds per Julian year:     31557600.000

       2) Suppose you wish to compute the number of julian centuries
          that have elapsed since the ephemeris epoch J1950 (beginning
          of the julian year 1950) at a particular UTC epoch.

          Use the LSK kernel below to load the leap seconds and time
          constants required for the conversions.

             naif0012.tls

          Example code begins here.

          /.
             Program jyear_ex2
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {
             /.
             Local constants.
             ./
             #define        UTCSTR        "2044-JUL-31"

             /.
             Local variables.
             ./
             SpiceDouble             et;
             SpiceDouble             centur;

             /.
             Load the LSK file.
             ./
             furnsh_c ( "naif0012.tls" );

             /.
             Convert input UTC string to Ephemeris Time.
             ./
             str2et_c ( UTCSTR, &et );
             printf ( "Input ephemeris time      : %16.3f\n", et );

             centur = ( et - unitim_c ( j1950_c(), "JED", "ET" ) );
             centur = centur / ( 100.0 * jyear_c() );

             printf ( "Centuries past J1950 epoch: %16.10f\n", centur );

             return ( 0 );

          }

          When this program was executed on a Mac/Intel/cc/64-bit
          platform, the output was:

          Input ephemeris time      :   1406808069.183
          Centuries past J1950 epoch:     0.9457905763

#### Restrictions

       None.

#### Literature_References

       [1]  P. Kenneth Seidelmann (Ed.), "Explanatory Supplement to the
            Astronomical Almanac," Page 8, University Science Books,
            1992.

#### Author_and_Institution

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

#### Version

       -CSPICE Version 1.0.1, 06-JUL-2021 (JDR)

           Edited the header to comply with NAIF standard. Added complete
           code examples.

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

#### Index_Entries

       Number of seconds per julian year

#### Link to routine jyear_c source file jyear_c.c

    Fri Dec 31 18:41:08 2021