' s ▁atmosphere . ▁Un like ▁a ▁ro cket ▁where ▁data ▁are ▁collected ▁during ▁a ▁brief ▁few ▁minutes , ▁bal lo ons ▁are ▁able ▁to ▁stay ▁al o ft ▁for ▁much ▁longer . ▁However , ▁even ▁at ▁such ▁alt itudes , ▁much ▁of ▁the ▁X - ray ▁spectrum ▁is ▁still ▁absor bed . ▁X - ray s ▁with ▁energ ies ▁less ▁than ▁ 3 5 ▁ke V ▁( 5 , 6 0 0 ▁a J ) ▁cannot ▁reach ▁bal lo ons . ▁On ▁July ▁ 2 1 , ▁ 1 9 6 4 , ▁the ▁C rab ▁Neb ula ▁super n ova ▁rem nant ▁was ▁discovered ▁to ▁be ▁a ▁hard ▁X - ray ▁( 1 5 – 6 0 ▁ke V ) ▁source ▁by ▁a ▁sc int ill ation ▁counter ▁flow n ▁on ▁a ▁bal lo on ▁launched ▁from ▁Palest ine , ▁Texas , ▁United ▁States . ▁This ▁was ▁likely ▁the ▁first ▁bal lo on - based ▁detection ▁of ▁X - ray s ▁from ▁a ▁discrete ▁cos mic ▁X - ray ▁source . ▁ ▁High - energy ▁foc using ▁teles cope ▁ ▁The ▁high - energy ▁foc using ▁teles cope ▁( HE FT ) ▁is ▁a ▁bal lo on - bor ne ▁experiment ▁to ▁image ▁ast ro phys ical ▁sources ▁in ▁the ▁hard ▁X - ray ▁( 2 0 – 1 0 0 ▁ke V ) ▁band . ▁Its ▁ma iden ▁flight ▁took ▁place ▁in ▁May ▁ 2 0 0 5 ▁from ▁Fort ▁Sum ner , ▁New ▁Mexico , ▁USA . ▁The ▁angular