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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

   SpiceDouble b1950_c ( void )

Abstract

   Return the Julian Date corresponding to Besselian Date 1950.0.

Required_Reading

   None.

Keywords

   CONSTANTS


Brief_I/O

   The function returns the Julian Date corresponding to Besselian
   date 1950.0.

Detailed_Input

   None.

Detailed_Output

   The function returns 2433282.42345905, the Julian Date corresponding
   to Besselian Date 1950.0 as reported by Lieske [1].

Parameters

   None.

Exceptions

   Error free.

Files

   None.

Particulars

   Lieske [1] defines a mapping from Julian Ephemeris Date 
   to Besselian:

      BE = 1900. + (JED - 2415020.31352)/365.242198781

   The inverse mapping being:

      JED = (BE - 1900.)*365.242198781 + 2415020.31352

Examples

   The following code fragment illustrates the use of b1950_c.

        /.
        Convert Julian Date to UTC seconds past the reference
        epoch (b1950_c).
        ./

        spref = ( jd - b1950_c() ) * spd_c();

Restrictions

   None.

Literature_References

   [1] Jay Lieske, ``Precession Matrix Based on IAU (1976)
       System of Astronomical Constants,'' Astron. Astrophys.
       73, 282-284 (1979).

Author_and_Institution

   W.L. Taber      (JPL)
   I.M. Underwood  (JPL)

Version

   -CSPICE Version 2.0.0, 01-SEP-2005 (EDW)

      This routine now returns the value reported in the Lieske
      paper:
         
         2433282.42345905
      
      The same value returned by the FORTRAN SPICELIB routine 
      B1950.
      
      This routine previously returned the value reported in the
      "Explanatory Supplement to the Astronomical Almanac", 1992, 
      page 699:
      
         2433282.423
         
      The ESAA value describing a truncation of the Lieske value.
      The difference between the two values expressed as seconds 
      yields approximately 39.662 seconds.

   -CSPICE Version 1.0.1, 08-FEB-1998 (EDW)

       Corrected and clarified header entries.

   -CSPICE Version 1.0.0, 25-OCT-1997 (EDW)

Index_Entries

   besselian date 1950.0
Wed Apr  5 17:54:28 2017