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