(S (S (S (BASENP (DT The) (NN space) (NN walk)) (VP (VP (VBD had) (RB not)) (VP (VBN been) (VP (VBN planned))))) (SBAR (IN until) (S (S (BASENP (DT the) (NN mission)) (VP (VP (VBD was) (ADVP (RB already))) (ADJP (JJ underway)))) (SBAR (WHADVP (WRB when)) (S (BASENP (DT the) (NN damage)) (VP (VBD was) (VP (ADVP (RB then)) (VBN detected)))))))) (PERIOD .))