A system for non-destructive evaluation of an object uses a spherical coordinate system to control two robotic arms. In some examples, the system includes a radiation source coupled to one robotic arm, a radiation detector coupled to the other robotic arm; and a control unit configured to determine, based on input, a first position located on a first surface of a first sphere within the spherical coordinate system; determine, based on the input, a second position located on a second surface of a second sphere within the spherical coordinate system, wherein the second position is located opposite a midpoint of the spherical coordinate system from the first position; and control a motion of the source robotic arm and the detector robotic arm such that the radiation source and the radiation detector move to different ones of the first position and the second position.