( ( Its ( main instrument ) ) ( ( ( was ( ( a Geiger ) counter ) ) ( used ( to ( measure ( ( the radiation ) ( in space ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP$ Its) (JJ main) (NN instrument)) (VP (VBD was) (ADVP (NP (DT a) (NN Geiger)) (RB counter)) (VP (VBN used) (S (VP (TO to) (VP (VB measure) (NP (NP (DT the) (NN radiation)) (PP (IN in) (NP (NN space))))))))) (. .)))
Its main instrument was a Geiger counter used to measure the radiation in space.
(ROOT (S (NP (NP (DT The) (`` `) (NN counting) ('' ') (NN instrument)) (NP (NN geiger) (NN counter))) (VP (VBZ is) (VP (VBN used) (S (VP (TO to) (VP (VB measure) (NP (NN radioactivity))))))) (. .)))