(S (S (S (BASENP (DT The) (NN team)) (VP (ADVP (RB originally)) (VP (VBD intended) (S (VP (TO to) (VP (VP (VB test) (PP (IN for) (BASENP (JJ possible) (NN human) (JJ magnetic) (NN field) (NN detection)))) (PP (IN by) (S (VP (VBG studying) (NP (NP (BASENP (DT the) (NN orientation)) (PP (IN of) (BASENP (NN sleeping) (NNS bags)))) (PP (IN in) (BASENP (JJ outdoor) (NNS campers))))))))))))) (CONJP (COMMA ,) (CC but)) (S (S (BASENP (PRP it)) (VP (VBD proved) (ADJP (JJ difficult) (S (VP (TO to) (VP (VB obtain) (BASENP (NN data)))))))) (SBAR (IN because) (S (BASENP (NNS humans)) (VP (ADVP (RB usually)) (VP (VBD slept) (PP (IN under) (BASENP (NNS tents))))))))) (PERIOD .))