( ( ( ( ( ( ( The ( infrared ( telescope 's ) ) ) photodetector ) ( must ( ( ( be ( subject ( to ( ( ( ( ( considerable cooling ) , ) e.g. ) , ) ( using ( liquid nitrogen ) ) ) ) ) ) , ) ( to ( avoid ( ( ( high dark ) - ) current ) ) ) ) ) ) , ) and ) ( it ( must ( be ( provided ( with ( a ( ( cold-shield ( to ( ( restrict ( ( its field-of-view ) ( -LRB- ( FOV -RRB- ) ) ) ) ( to background ) ) ) ) ( thermal radiation ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (DT The) (JJ infrared) (NN telescope) (POS 's)) (NN photodetector)) (VP (MD must) (VP (VB be) (ADJP (JJ subject) (PP (TO to) (S (NP (NP (JJ considerable) (NN cooling)) (, ,) (NP (NNP e.g.)) (, ,)) (VP (VBG using) (NP (JJ liquid) (NN nitrogen)))))) (, ,) (S (VP (TO to) (VP (VB avoid) (ADJP (ADJP (RB high) (JJ dark)) (: -) (ADJP (JJ current))))))))) (, ,) (CC and) (S (NP (PRP it)) (VP (MD must) (VP (VB be) (VP (VBN provided) (PP (IN with) (NP (DT a) (ADJP (JJ cold-shield) (S (VP (TO to) (VP (VB restrict) (NP (NP (PRP$ its) (NN field-of-view)) (PRN (-LRB- -LRB-) (NP (NNP FOV)) (-RRB- -RRB-))) (PP (TO to) (NP (NN background))))))) (JJ thermal) (NN radiation))))))) (. .)))
The infrared telescope's photodetector must be subject to considerable cooling, e.g., using liquid nitrogen, to avoid high dark- current, and it must be provided with a cold-shield to restrict its field-of-view (FOV) to background thermal radiation.
(ROOT (S (NP (NN Liquid) (NN nitrogen)) (VP (VBZ is) (VP (VBN used) (PP (IN for) (NP (NP (VBG cooling) (NNS detectors)) (PP (IN of) (NP (JJ infrared) (NNS telescopes))))))) (. .)))