, ▁which ▁will ▁have ▁many ▁universal ▁or bits ▁in ▁LE O ▁with ▁ 3 0 ▁to ▁ 5 0 ▁sat ell ites ▁per ▁orb ital ▁plane ▁and ▁alt itude . ▁Trad itionally , ▁the ▁most ▁populated ▁LE O ▁or bits ▁have ▁been ▁a ▁number ▁of ▁sun - s ynchronous ▁sat ell ites ▁that ▁keep ▁a ▁constant ▁angle ▁between ▁the ▁Sun ▁and ▁the ▁orb ital ▁plane , ▁making ▁Earth ▁observation ▁easier ▁with ▁consistent ▁sun ▁angle ▁and ▁light ing . ▁Sun - s ynchronous ▁or bits ▁are ▁polar , ▁meaning ▁they ▁cross ▁over ▁the ▁polar ▁regions . ▁LE O ▁sat ell ites ▁orbit ▁in ▁many ▁plan es , ▁typically ▁up ▁to ▁ 1 5 ▁times ▁a ▁day , ▁causing ▁frequent ▁approaches ▁between ▁objects . ▁The ▁density ▁of ▁sat ell ites — both ▁active ▁and ▁der el ict — is ▁much ▁higher ▁in ▁LE O . ▁ ▁Or bits ▁are ▁affected ▁by ▁gravit ational ▁perturb ations ▁( which ▁in ▁LE O ▁include ▁une ven ness ▁of ▁the ▁Earth ' s ▁gravit ational ▁field ▁due ▁to ▁variations ▁in ▁the ▁density ▁of ▁the ▁planet ), ▁and ▁coll isions ▁can ▁occur ▁from ▁any ▁direction . ▁Imp act s ▁between ▁orbit ing ▁sat ell ites ▁can ▁occur ▁at ▁up ▁to ▁ 1 6   km / s ▁for ▁a ▁theoretical ▁head - on ▁impact ; ▁the ▁closing ▁speed ▁could ▁be ▁twice ▁the ▁orb ital ▁speed . ▁The ▁ 2 0 0 9 ▁satellite ▁collision ▁occurred ▁at ▁a ▁closing ▁speed ▁of ▁ 1 1 . 7   km / s ,