KEPLER_VDISK

          KEPLER_VDISK is a variable that indicates the disk  systemic  velocity
    (in  km/s).   The value is always used to define the velocity field (see KE-
    PLER_VELO result variable).

      However, for the radial profile, the usage depends on the /VSYSTEM option.
    When /VSYSTEM is not present, the radial profile is  taken  as  the  maximum
    brightness of the integrated, velocity aligned, spectrum for at each radius.
    When /VSYSTEM option is present, the radial profile is taken at the velocity
    KEPLER_VDISK.