To measure the prowess of North Korean missiles, researchers spy with open-source clues

As North Korean missiles fly farther and more frequently under Kim Jong-un, the outside world watches warily, using a network of early-warning radar, sensors and satellites that track the test...

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JUDY WOODRUFF: Over the last two weeks, Miles O'Brien has taken us on a tour of what's publiclyknown about North Korea's nuclear weapons program.In the third and final part of his series, Miles looks at how those bombs might be delivered.Tonight, on the Leading Edge of science, the sleuths searching through open-source cluesto North Korea's fast-developing missile program.MILES O'BRIEN: North Korean missiles are flying much farther and much more frequently sinceKim Jong-un became supreme leader in 2011.He has reigned over more than 80 launches so far.The outside world watches warily with a network of early warning radar, sensors and satellitesthat track the missiles in real time to be sure they are indeed tests.Once the basic d...