s ▁in ▁ 1 9 5 9 . ▁ ▁In ▁the ▁late ▁ 1 9 7 0 s ▁they ▁produced ▁experimental ▁mas er ▁oscill ators ▁for ▁N RL , ▁which ▁eventually ▁led ▁to ▁space - based ▁G PS ▁atomic ▁clock s . ▁ ▁H RL ▁began ▁research ▁on ▁ion ▁prop ulsion ▁in ▁ 1 9 6 0 . ▁This ▁research ▁led ▁to ▁the ▁Hugh es ▁developed ▁x en on ▁ion ▁prop ulsion ▁system ▁( X IP S . ▁ ▁X IP S ▁was ▁used ▁as ▁the ▁primary ▁prop ulsion ▁system ▁on ▁NASA ' s ▁Deep ▁Space ▁ 1 ▁( launch ed ▁in ▁ 1 9 9 8 ). ▁ ▁It ▁is ▁a ▁standard ▁option ▁for ▁primary ▁station keep ing ▁on ▁the ▁Hugh es / B oe ing ▁ 6 0 1 HP ▁( first ▁use : ▁P AS - 5 , ▁ 1 9 9 7 ) ▁and ▁the ▁ 7 0 2 ▁( first ▁use : ▁Gal axy - X I , ▁ 1 9 9 9 ) ▁ge ost ation ary ▁satellite ▁families . ▁ ▁H RL ▁claims ▁to ▁have ▁developed ▁the ▁liquid ▁cry stal ▁watch ▁in ▁ 1 9 7 5 . ▁ ▁H RL ' s ▁Sy N AP SE ▁neur omorphic ▁chip ▁is ▁the ▁first ▁chip ▁to ▁learn ▁like ▁the ▁brain ▁by ▁alter ing ▁syn aps es ▁( list ed ▁as ▁one ▁of ▁M IT ▁Te ch ▁Review ▁top ▁ten ▁break through ▁techn ologies ) ▁( 2 0 1 0 s ). ▁ ▁Develop ed ▁world ' s