▁consum ers ▁by ▁collect ing ▁partic ulate ▁de br is ▁and ▁g ase ous ▁eff lu ents ▁from ▁accessible ▁regions ▁of ▁the ▁atmosphere ▁in ▁support ▁of ▁the ▁Limited ▁N uc lear ▁Test ▁Ban ▁Tre aty ▁of ▁ 1 9 6 3 . ▁ ▁Fe atures ▁The ▁Constant ▁Phoenix ' s ▁modifications ▁are ▁primarily ▁related ▁to ▁the ▁aircraft ' s ▁on - board ▁atmos pher ic ▁collection ▁suite , ▁which ▁allows ▁the ▁mission ▁crew ▁to ▁detect ▁radio active ▁de br is ▁" cloud s " ▁in ▁real ▁time . ▁The ▁aircraft ▁is ▁equ ipped ▁with ▁external ▁flow - through ▁devices ▁to ▁collect ▁particul ates ▁on ▁filter ▁paper ▁and ▁a ▁compress or ▁system ▁for ▁whole ▁air ▁samples ▁collected ▁in ▁high - press ure ▁holding ▁spher es . ▁Despite ▁the ▁different ▁design ations , ▁both ▁the ▁C ▁and ▁W ▁carry ▁the ▁same ▁mission ▁equipment ▁( similar ▁to ▁the ▁RC - 1 3 5 V ▁and ▁W ▁aircraft ). ▁ ▁The ▁interior ▁seats ▁ 3 3 ▁people , ▁including ▁the ▁co ck pit ▁crew , ▁maintenance ▁personnel , ▁and ▁special ▁equipment ▁operators ▁from ▁the ▁Air ▁Force ▁Techn ical ▁App lications ▁Center . ▁On ▁oper ational ▁sort ies , ▁the ▁crew ▁is ▁minim ized ▁to ▁just ▁pil ots , ▁navig ator , ▁and ▁special - equ ip ment ▁operators , ▁to ▁reduce ▁radiation ▁expos ure ▁to ▁mission - ess ential ▁personnel ▁only . ▁ ▁V ela ▁Inc ident ▁W C - 1 3 5 B ▁aircraft ▁fle w ▁ 2 5 ▁sort ies ▁in ▁ 1 9 7