NAME:
  ppolepa
 PURPOSE:   (one line only)
  Compute the position angle of Pluto's pole on the plane of the sky
 DESCRIPTION:
 CATEGORY:
  Astronomy
 CALLING SEQUENCE:
  ppolepa,jd,posang
 INPUTS:
  jd - Julian date for the position angle calculation
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
 OUTPUTS:
  posang - position angle of the projected pole, E of N, radians
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
  There is a hardcoded value for the inclination and node of Charon's orbit
  that is used to compute the pole of Charon's orbit.  This pole is assumed
  be coincident with Pluto's rotation pole.
 PROCEDURE:
 MODIFICATION HISTORY:
  2011/11/29, Written by Marc W. Buie, Southwest Research Institute
                guided by PPOLEPA.F written by David J. Tholen