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