▁boost er . ▁Although ▁NASA ▁and ▁the ▁United ▁States ▁Air ▁Force ▁now ▁require ▁upper - stage ▁pass iv ation , ▁other ▁launch ers ▁do ▁not . ▁Lower ▁stages , ▁like ▁the ▁Space ▁Sh utt le ' s ▁solid ▁ro cket ▁boost ers ▁or ▁Apol lo ▁program ' s ▁Sat urn ▁IB ▁launch ▁vehicles , ▁do ▁not ▁reach ▁orbit . ▁ ▁On ▁ 1 1 ▁March ▁ 2 0 0 0 ▁a ▁Chinese ▁Long ▁March ▁ 4 ▁C BER S - 1 ▁upper ▁stage ▁expl oded ▁in ▁orbit , ▁creating ▁a ▁de br is ▁cloud . ▁A ▁Russian ▁B riz - M ▁boost er ▁stage ▁expl oded ▁in ▁orbit ▁over ▁South ▁Australia ▁on ▁ 1 9 ▁February ▁ 2 0 0 7 . ▁La unch ed ▁on ▁ 2 8 ▁February ▁ 2 0 0 6 ▁carrying ▁an ▁Arab s at - 4 A ▁communic ations ▁satellite , ▁it ▁mal function ed ▁before ▁it ▁could ▁use ▁up ▁its ▁prop ell ant . ▁Although ▁the ▁explos ion ▁was ▁captured ▁on ▁film ▁by ▁astronom ers , ▁due ▁to ▁the ▁orbit ▁path ▁the ▁de br is ▁cloud ▁has ▁been ▁difficult ▁to ▁measure ▁with ▁rad ar . ▁By ▁ 2 1 ▁February ▁ 2 0 0 7 , ▁over ▁ 1 , 0 0 0 ▁fragments ▁were ▁identified . ▁A ▁ 1 4 ▁February ▁ 2 0 0 7 ▁break up ▁was ▁recorded ▁by ▁Cel est rak . ▁E ight ▁break ups ▁occurred ▁in ▁ 2 0 0 6 , ▁the ▁most ▁since ▁ 1 9 9 3