{HEAD ~ Each composite illumination beam} is directed to be {TAIL ~ incident} upon a separate predetermined location on the subreflector which directs the illumination beams towards the main reflector 
is directed to be
{ HEAD ~ Each composite illumination beam } is directed to be { TAIL ~ incident } upon a separate predetermined location on the subreflector which directs the illumination beams towards the main reflector
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH