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 j2100_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
       j2100_c ( Julian Date of 2100 JAN 1.5 )

       SpiceDouble j2100_c ( void )
#### Abstract
       Return the Julian Date of 2100 JAN 01 12:00:00 (2100 JAN 1.5).
#### Required_Reading
       None.
#### Keywords
       CONSTANTS
#### Brief_I/O
       The function returns the Julian Date of 2100 JAN 01 12:00:00
       (2100 JAN 1.5).
#### Detailed_Input
       None.
#### Detailed_Output
       The function returns 2488070.0, the Julian Date corresponding
       to 2100 JAN 01 12:00:00 (2100 JAN 1.5).
#### Parameters
       None.
#### Exceptions
       Error free.
#### Files
       None.
#### Particulars
       The function always returns the constant value shown above.
#### 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 double precision value for the J2100 date.

          Example code begins here.

          /.
             Program j2100_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {
             /.
             Display the J2100 date in 16.8 floating point format
             ./
             printf ( "J2100 date: %16.8f\n", j2100_c() );

             return ( 0 );
          }

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

          J2100 date: 2488070.00000000

       2) Convert an input time in UTC format to TDB seconds past the
          following reference epochs:

             - Besselian date 1900 and 1950; and

             - Julian date 1900, 1950, 2000 and 2100.

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

             naif0012.tls

          Example code begins here.

          /.
             Program j2100_ex2
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {
             /.
             Local constants.
             ./
             #define        UTCSTR        "1991-NOV-26"

             /.
             Local variables.
             ./
             SpiceDouble             et;
             SpiceDouble             jed;

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

             /.
             Convert input UTC string to Ephemeris Time.
             ./
             str2et_c ( UTCSTR, &et );
             printf ( "Input ephemeris time  : %20.3f\n\n", et );

             /.
             Convert the Ephemeris Time to Julian ephemeris date, i.e.
             Julian date relative to TDB time scale.
             ./
             jed = unitim_c ( et, "ET", "JED" );

             /.
             Convert Julian Date to TDB seconds past the reference epochs
             and output the results.
             ./
             printf ( "TDB seconds past B1900: %20.3f\n",
                      ( jed - b1900_c() ) * spd_c()     );
             printf ( "TDB seconds past B1950: %20.3f\n",
                      ( jed - b1950_c() ) * spd_c()     );
             printf ( "TDB seconds past J1900: %20.3f\n",
                      ( jed - j1900_c() ) * spd_c()     );
             printf ( "TDB seconds past J1950: %20.3f\n",
                      ( jed - j1950_c() ) * spd_c()     );
             printf ( "TDB seconds past J2000: %20.3f\n",
                      ( jed - j2000_c() ) * spd_c()     );
             printf ( "TDB seconds past J2100: %20.3f\n",
                      ( jed - j2100_c() ) * spd_c()     );

             return ( 0 );
          }

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

          Input ephemeris time  :       -255614341.817

          TDB seconds past B1900:       2900118570.055
          TDB seconds past B1950:       1322272271.321
          TDB seconds past J1900:       2900145658.183
          TDB seconds past J1950:       1322265658.183
          TDB seconds past J2000:       -255614341.817
          TDB seconds past J2100:      -3411374341.817
#### Restrictions
       None.
#### Literature_References
       None.
#### Author_and_Institution
       J. Diaz del Rio     (ODC Space)
       W.L. Taber          (JPL)
       I.M. Underwood      (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) (IMU)
#### Index_Entries
       julian date of 2100 jan 1.5
#### Link to routine j2100_c source file j2100_c.c

    Fri Dec 31 18:41:08 2021