Unlike LADAR scanners, RGB, or Bumblebee cameras RADAR allows the vehicle to move even if visibility (i.e. fog, smoke, rain, dust) is poor. Eaton Vorad  provides three of Spirit's seven RADAR units and has a truck RADAR simulator. Spirit's RADAR range is from over 1 foot to 5 miles!

RADAR "sees" farthest of all autonomous tools and 3D MMW works best.

RADAR:  RA(dio) D(etecting) A(nd) R(anging)