NAME:
  synthocc
 PURPOSE:   (one line only)
  Generate simulated occultation data
 DESCRIPTION:
 CATEGORY:
  Occultations
 CALLING SEQUENCE:
  synthocc,shape
 INPUTS:
  shape - input shape to use for the object.  There are two options supported,
             either an ellipse or a numerical hull.
          ellipse - five element vector (float or double)
             0 - semi-major axis of ellipse
             1 - semi-minor axis of ellipse
             2 - x position of center
             3 - y position of center
             4 - position angle of ellipse (radians)
          hull - string with the file name to read, this file should have
                  a list of xi,eta points that define the hull
          all spatial values should be in kilometers
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  FNCONFIG - name of configuration file (overrides xtrack.in),
              the default is config.ini but if the configuration file
              is not found then operation reverts to using xtrack.in
              The minimal content of the config file must have:
  FNSITES - name of the file with site location information (default=sites.dat)
  FNEVENTS - name of occultation events file (default=events.dat)
  FNXTRACK - Name of the file with the crosstrack position information,
              default='crosstrack.dat'
  XYFLAG   - Flag, if set reverses the first axis of points in a hull shape
               file.  The values plotted are always sky normal xi/eta
               coordinates which are in a left-handed coordinate system.
               This flag lets you use a right-handed set of x/y coordinates
               in the file and they will be inverted left-to-right.
 OUTPUTS:
 KEYWORD OUTPUT PARAMETERS:
 CONFIGURATION:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  Written by Marc W. Buie, Southwest Research Institute, 2023/09/14