NAME:
  patlatlon
 PURPOSE:   (one line only)
  Compute viewing and illumination geometry for Patroclus-Menoetius system
 DESCRIPTION:
 CATEGORY:
  Astronomy
 CALLING SEQUENCE:
  patlatlon,jd,elat,elon,slat,slon,polang,phang,earth,sun,elong
 INPUTS:
  jd - Julian date for the geometry calculation
               (double precision, scalar or vector)
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  ORBIT - String with name of orbit solution to use, the default
             is to use the most recent orbit.  This default can change
             as new orbits are added.
            Currently supported:
              'owen1' - From Bill Owen, JPL - not much data
              'grundy1' - From Will Grundy
 OUTPUTS:
  elat - Latitude of the sub-earth point [radians]
  elon - East longitude of the sub-earth point [radians]
  slat - Latitude of the sub-solar point [radians]
  slon - East longitude of the sub-solar point [radians]
  polang - Position angle of Pluto's north pole, measured eastward from
              north [radians]
  phang - Solar phase angle (Sun-Pluto-Earth angle) [radians]
  earth - Geocentric distance [AU]
  sun   - Heliocentric distance [AU]
  elong - Solar elongation [radians]
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
  This is a slow routine for vector calls.  Some of the supporting routines
    cannot handle vectorized input so each output value is computed in an
    explicit loop.
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  2011/12/30 - Written by Marc W. Buie, Southwest Research Institute
                 code based on fortran routines written by David Tholen
  2012/06/04 - MWB, fixed typo on 2012 orbit.
  2013/06/06 - MWB, added elong output.
  2018/02/12 - MWB, added Grundy et al., 2018 orbit