A scraper mirror reflects the beams to {HEAD ~ a thermal imager} which reflects {TAIL ~ the beams} to a pair of NaCl beamsplitters 
reflects
A scraper mirror reflects the beams to { HEAD ~ a thermal imager } which reflects { TAIL ~ the beams } to a pair of NaCl beamsplitters
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH