▁landing ▁site ▁( RT LS ) ▁weather . ▁Later ▁at ▁the ▁post - launch ▁news ▁conference , ▁Mr . ▁Mos es ▁explained ▁that ▁his ▁decision ▁was ▁based ▁on ▁the ▁fact ▁although ▁a ▁few ▁show ers ▁that ▁were ▁po pping ▁up ▁within ▁the ▁ ▁radius ▁from ▁the ▁Sh utt le ▁Land ing ▁Fac ility ▁at ▁R T LS ▁landing ▁were ▁a ▁launch ▁constraint , ▁the ▁show ers ▁would ▁have ▁been ▁cleared ▁by ▁the ▁time ▁of ▁a ▁R T LS ▁landing ▁( if ▁it ▁did ) ▁ 3 5 ▁minutes ▁later . ▁ ▁At ▁the ▁end ▁of ▁the ▁poll ▁Le in bach ▁told ▁the ▁crew ▁" Good ▁luck ▁to ▁you ▁and ▁your ▁crew ▁on ▁the ▁final ▁flight ▁of ▁this ▁true ▁American ▁icon . ▁Good ▁luck , ▁god speed ▁and ▁have ▁a ▁little ▁fun ▁up ▁there " ▁to ▁which ▁commander ▁Chris ▁Fer g us on ▁replied ▁" Thanks ▁to ▁you ▁and ▁your ▁team ▁Mike , ▁We ' re ▁comple ting ▁a ▁chapter ▁of ▁a ▁journey ▁that ▁will ▁never ▁end . ▁The ▁crew ▁of ▁Atl ant is ▁is ▁ready ▁to ▁launch ". ▁ ▁At ▁T - 3 1 ▁seconds , ▁just ▁before ▁Atl ant iss ▁computers ▁were ▁supposed ▁to ▁take ▁control ▁of ▁the ▁flight , ▁the ▁launch ▁count down ▁clock ▁stopped . ▁This ▁was ▁because ▁of ▁a ▁lack ▁of ▁an ▁indic ation ▁that ▁the ▁G ase ous ▁O xygen ▁Vent ▁Arm ▁had ▁ret ract ed ▁and ▁properly ▁l atch ed , ▁a ▁problem ▁that ▁had ▁never ▁occurred ▁during ▁previous ▁launch es ▁in ▁the ▁program ' s ▁history