Procedure

   void radrec_c ( SpiceDouble range, 
                   SpiceDouble ra, 
                   SpiceDouble dec, 
                   SpiceDouble rectan[3] ) 

Abstract

 
   Convert from range, right ascension, and declination to rectangular
   coordinates.
 

Required_Reading

 
   None. 
 

Keywords

 
   CONVERSION,   COORDINATES 
 

Brief_I/O

 
   VARIABLE  I/O  DESCRIPTION 
   --------  ---  --------------------------------------------------- 
   range      I   Distance of a point from the origin. 
   ra         I   Right ascension of point in radians. 
   dec        I   Declination of point in radians. 
   rectan     O   Rectangular coordinates of the point.
 

Detailed_Input

 
   range      is the distance of the point from the origin.  Output
              units are the same as the units associated with `range.'
 
   ra         is the right ascension of the input point:  the angular
              distance measured toward the east from the prime meridian
              to the meridian containing the input point. The direction
              of increasing right ascension is from the +X axis towards
              the +Y axis.

              The range (i.e., the set of allowed values) of 
              `ra' is unrestricted.  Units are radians.

   dec        is the declination of the point.  This is the angular 
              distance from the XY plane to the point.  

              The range of `dec' is unrestricted.  Units are radians.
 

Detailed_Output

 
   rectan     is the array containing the rectangular coordinates of 
              the point.  The output units associated with `rectan'
              are those associated with the input `range.'

Parameters

 
   None. 
 

Exceptions

 
   Error free. 
 

Files

 
   None. 
 

Particulars

   None.
 

Examples

 
   The following code fragment converts right ascension and 
   declination from the B1950 reference frame to the J2000 frame.
 
      #include "SpiceUsr.h"

      SpiceDouble      ra;
      SpiceDouble      dec; 
      SpiceDouble      r;
      SpiceDouble      rotab  [ 3 ][ 3 ]; 
      SpiceDouble      oldvec [ 3 ];
      SpiceDouble      newvec [ 3 ];


      radrec_c ( 1.0, ra, dec, oldvec );

      pxform_c ( "B1950", "J2000", 0.0, rotab );

      mxv_c    ( rotab,   oldvec, newvec );
      recrad_c ( newvec,  &r,     &ra,    &dec ); 
 
 

Restrictions

 
   None. 
 

Literature_References

 
   "Celestial Mechanics, A Computational Guide for the Practitioner" 
   by Laurence G. Taff 
 

Author_and_Institution

 
   N.J. Bachman    (JPL)
   H.A. Neilan     (JPL) 
   E.D. Wright     (JPL)
 

Version

 
   -CSPICE Version 1.0.2, 28-JUL-2003 (NJB) 
   
      Various header corrections were made.

   -CSPICE Version 1.0.1, 13-APR-2000 (NJB) 
   
      Made some minor updates and corrections in the code example.
      
   -CSPICE Version 1.0.0, 08-FEB-1998 (EDW)

Index_Entries

 
   range ra and dec to rectangular coordinates 
   right_ascension and declination to rectangular 
 

Link to routine radrec_c source file radrec_c.c