/*

-Procedure recrad_c ( Rectangular coordinates to RA and DEC )

-Abstract
 
   Convert rectangular coordinates to range, right ascension, and
   declination.

-Disclaimer

   THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE
   CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S.
   GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE
   ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE
   PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS"
   TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY
   WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A
   PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC
   SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE
   SOFTWARE AND RELATED MATERIALS, HOWEVER USED.

   IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA
   BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT
   LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND,
   INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS,
   REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE
   REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY.

   RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF
   THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY
   CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE
   ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE.

-Required_Reading
 
   None. 
 
-Keywords
 
   CONVERSION,  COORDINATES 
 
*/

   #include "SpiceUsr.h"
   #undef    recrad_c


   void recrad_c ( ConstSpiceDouble    rectan[3],
                   SpiceDouble       * range,
                   SpiceDouble       * ra,
                   SpiceDouble       * dec      ) 

/*

-Brief_I/O
 
   VARIABLE  I/O  DESCRIPTION 
   --------  ---  -------------------------------------------------- 
   rectan     I   Rectangular coordinates of a point. 
   range      O   Distance of the point from the origin. 
   ra         O   Right ascension in radians. 
   dec        O   Declination in radians. 
 
-Detailed_Input
 
   rectan     The rectangular coordinates of a point. 
 
-Detailed_Output
 
   range      is the distance of the point `rectan' from the origin. 

              The units associated with `range' are those associated
              with the input `rectan'.
 
   ra         is the right ascension of `rectan'.  This is 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.
              
              `ra' is output in radians.  The range of `ra' is [0, 2*pi]. 
 
 
   dec        is the declination of `rectan'.  This is the angle from
              the XY plane of the ray from the origin through the
              point.
 
              `dec' is output in radians.  The range of `dec' is
              [-pi/2, pi/2].
 
-Parameters
 
   None. 
 
-Exceptions
 
   Error free. 

   1) If the X and Y components of `rectan' are both zero, the
      right ascension is set to zero.

   2) If `rectan' is the zero vector, right ascension and declination
      are both set to zero.
 
-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      mtrans  [ 3 ][ 3 ]; 
      SpiceDouble      v1950   [ 3 ];
      SpiceDouble      v2000   [ 3 ];

      /.
      Convert RA and DEC to a 3-vector expressed in the B1950 frame.
      ./
      radrec_c ( 1.0, ra, dec, v1950 );

      /.
      We use the CSPICE routine pxform_c to obtain the transformation
      matrix for converting vectors between the B1950 and J2000
      reference frames.  Since both frames are inertial, the input time
      value we supply to pxform_c is arbitrary.  We choose zero seconds
      past the J2000 epoch as the input value.
      ./
      pxform_c ( "B1950", "J2000", 0.0, mtrans );

      /.
      Transform the vector to the J2000 frame.
      ./
      mxv_c    ( mtrans, v1950, v2000 );

      /.
      Find the RA and DEC of the J2000-relative vector.
      ./
      recrad_c ( v2000, &r, &ra, &dec ); 

 
-Restrictions
 
   None. 
 
-Author_and_Institution
 
   N.J. Bachman    (JPL)
   H.A. Neilan     (JPL) 
   E.D. Wright     (JPL)
 
-Literature_References
 
   None. 
 
-Version
 
   -CSPICE Version 1.1.2, 30-JUL-2003 (NJB)

       Various header corrections were made.

   -CSPICE Version 1.1.0, 22-OCT-1998 (NJB)

      Made input vector const.

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

-Index_Entries
 
   rectangular coordinates to ra and dec 
   rectangular to right_ascension and declination 
 
-&
*/

{ /* Begin recrad_c */

   /*
   Call reclat_c to perform the conversion to angular terms.
   */

   reclat_c ( rectan, range, ra, dec );


   /*
   Right ascension is always in the domain [0, 2Pi].  Rectan_c returns
   ra in the domain [ -Pi, Pi ].  If ra is negative, add 2 Pi to map the
   value to the correct domain
   */

   if ( *ra < 0. )
      {
      *ra = *ra + twopi_c();
      }



} /* End recrad_c */
