<Dl> <Dt> Electronic - reconnaissance </Dt> <Dd> Signals intelligence, intercepts stray radio waves . Samos - F is the earliest known . </Dd> </Dl> <Dt> Electronic - reconnaissance </Dt> <Dd> Signals intelligence, intercepts stray radio waves . Samos - F is the earliest known . </Dd> <Dl> <Dt> Radar imaging </Dt> <Dd> Most space - based radars use synthetic aperture radar . Can be used at night or through cloud cover . Earliest known are the Soviet US - A series . </Dd> </Dl>

Which series of reconnaissance satellites did the us launch in 1972