2 1 - cent imeter ▁H   I ▁line ▁in ▁ 1 9 5 1 . ▁ ▁Radio ▁inter fer ometry ▁Radio ▁inter fer ometry ▁was ▁pione ered ▁in ▁ 1 9 4 6 , ▁when ▁Joseph ▁La de ▁P aw sey , ▁Ruby ▁Pay ne - Sc ott ▁and ▁L inds ay ▁McC ready ▁used ▁a ▁single ▁anten na ▁at op ▁a ▁sea ▁cl iff ▁to ▁observe ▁ 2 0 0   M Hz ▁solar ▁radiation . ▁Two ▁incident ▁be ams , ▁one ▁directly ▁from ▁the ▁sun ▁and ▁the ▁other ▁reflected ▁from ▁the ▁sea ▁surface , ▁generated ▁the ▁necessary ▁inter ference . ▁The ▁first ▁multi - rece iver ▁inter fer ometer ▁was ▁built ▁in ▁the ▁same ▁year ▁by ▁Martin ▁R yle ▁and ▁Von berg . ▁In ▁ 1 9 6 0 , ▁R yle ▁and ▁Anton y ▁H ew ish ▁published ▁the ▁technique ▁of ▁a pert ure ▁synth esis ▁to ▁analyze ▁inter fer ometer ▁data . ▁The ▁a pert ure ▁synth esis ▁process , ▁which ▁involves ▁aut oc or rel ating ▁and ▁discrete ▁Fourier ▁transform ing ▁the ▁incoming ▁signal , ▁re co vers ▁both ▁the ▁spatial ▁and ▁frequency ▁variation ▁in ▁flux . ▁The ▁result ▁is ▁a ▁ 3 D ▁image ▁whose ▁third ▁axis ▁is ▁frequency . ▁For ▁this ▁work , ▁R yle ▁and ▁H ew ish ▁were ▁joint ly ▁awarded ▁the ▁ 1 9 7 4 ▁Nobel ▁Prize ▁in ▁Physics . ▁ ▁X - ray ▁spect ro sc opy ▁ ▁Stars ▁and ▁their ▁properties ▁ ▁Chem ical ▁properties ▁Newton ▁used ▁a ▁pr