▁the ▁Explorer ▁ 5 1 ▁mission ▁was ▁to ▁investigate ▁the ▁therm os phere , ▁with ▁emphas is ▁on ▁the ▁energy ▁transfer ▁and ▁processes ▁that ▁govern ▁its ▁state . ▁The ▁study ▁of ▁phot och em ical ▁processes ▁accomp any ing ▁the ▁absor ption ▁of ▁solar ▁U V ▁radiation ▁in ▁the ▁earth ' s ▁atmosphere ▁was ▁accomplished ▁by ▁making ▁closely ▁coordin ated ▁measurements ▁of ▁react ing ▁constitu ents ▁and ▁the ▁solar ▁input . ▁ ▁The ▁data ▁from ▁Explorer ▁ 5 1 ▁served , ▁among ▁other ▁things , ▁to ▁obtain ▁the ▁angular ▁load ▁distribution ▁around ▁the ▁satellite ▁and ▁compare ▁it ▁with ▁the ▁data ▁of ▁Explorer ▁ 3 1 ▁and ▁model ▁the ▁hydro x yl ▁ion ▁em issions ▁in ▁the ▁Earth ' s ▁atmosphere . ▁ ▁Inst ru ments ▁The ▁satellite ▁carried ▁instruments ▁to ▁measure ▁ult rav io let ▁solar ▁radiation , ▁temperature , ▁composition ▁and ▁density ▁of ▁the ▁positive ▁ ions , ▁of ▁the ▁neutral ▁particles ▁and ▁of ▁the ▁electrons , ▁to ▁measure ▁atmos pher ic ▁g low ▁em issions , ▁the ▁energy ▁spect ra ▁of ▁the ▁photo elect rons ▁and ▁the ▁pro tons ▁and ▁electrons ▁flows ▁with ▁energ ies ▁up ▁to ▁ 2 5 ▁ke V . ▁ ▁References ▁ ▁Category : Space craft ▁launched ▁in ▁ 1 9 7 3 ▁Category : Ex pl or ers ▁program ▁( N AS A ) ▁Category : Space craft ▁launched ▁by ▁D elta ▁rock ets <0x0A> </s> ▁Ot ter ▁Kill ▁is ▁a ▁ ▁trib ut ary ▁of ▁M ood na ▁Creek ▁that ▁flows ▁through ▁central ▁Orange ▁County