- based ▁guidance ▁for ▁inter ception . ▁One ▁of ▁the ▁I - 1 5 s ▁configured ▁for ▁night ▁operations , ▁fitted ▁with ▁trac er ▁and ▁explos ive ▁. 3 0 ▁r ounds , ▁scored ▁a ▁day light ▁double ▁victory ▁against ▁B f ▁ 1 0 9 s ▁in ▁the ▁closing ▁stages ▁of ▁the ▁war . ▁ ▁Nevertheless , ▁ ▁some ▁new ▁techn ologies ▁appeared ▁to ▁offer ▁potential ▁ways ▁to ▁improve ▁night - f ight ing ▁cap ability . ▁During ▁the ▁ 1 9 3 0 s , ▁considerable ▁development ▁of ▁inf ra red ▁detect ors ▁occurred ▁among ▁all ▁of ▁the ▁major ▁forces , ▁but ▁in ▁practice , ▁these ▁proved ▁almost ▁unus able . ▁The ▁only ▁such ▁system ▁to ▁see ▁any ▁sort ▁of ▁w ides p read ▁oper ational ▁use ▁was ▁the ▁Sp anner ▁An lage ▁system ▁used ▁on ▁the ▁D orn ier ▁Do ▁ 1 7 Z ▁night ▁f igh ters ▁of ▁the ▁Luft wa ffe . ▁These ▁were ▁often ▁also ▁fitted ▁with ▁a ▁large ▁IR ▁search light ▁to ▁improve ▁the ▁amount ▁of ▁light ▁being ▁returned . ▁ ▁Im medi ately ▁prior ▁to ▁the ▁opening ▁of ▁the ▁war , ▁rad ar ▁was ▁introduced ▁operation ally ▁for ▁the ▁first ▁time . ▁Initial ly , ▁these ▁systems ▁were ▁unw ield y , ▁and ▁development ▁of ▁IR ▁systems ▁continued . ▁Real izing ▁that ▁rad ar ▁was ▁a ▁far ▁more ▁practical ▁solution ▁to ▁the ▁problem , ▁Robert ▁Watson - W att ▁handed ▁the ▁task ▁of ▁developing ▁a ▁rad ar ▁suitable ▁for ▁aircraft ▁use ▁to ▁' T aff