(S (S (NP (BASENP (DT The) (NNS satellites)) (PRN (COMMA ,) (SBAR (WHNP (DT both) (WHPP (IN of) (WHNP (WDT which)))) (S (VP (VP (VBD had) (NP (BASENP (DT a) (NN mass)) (PP (IN in) (NP (BASENP (NN excess)) (PP (IN of) (BASENP (NN 450) (NNS kilograms))))))) (CONJP (COMMA ,) (CC and)) (VP (VBD were) (VP (VBN traveling) (PP (IN at) (NP (NP (BASENP (QP (RB approximately) (NN 17,500)) (NNS miles)) (PP (IN per) (BASENP (NN hour)))) (PRN (LRB -LRB-) (BASENP (NN 28,150) (NN km/hour)) (RRB -RRB-))))))))) (COMMA ,))) (VP (VBD collided) (PP (NP (BASENP (NN 491) (NNS miles)) (PRN (LRB -LRB-) (BASENP (NN 790) (SYM km)) (RRB -RRB-))) (PP (IN above) (BASENP (DT the) (NN earth)))))) (PERIOD .))