MIDDLE RIVER, MARYLAND- The second of two helium-filled airships was launched by the U.S. military to test an East Coast missile defense system.

The launch was from the Army's Aberdeen Proving Ground completes the aeronautical part of what's known as JLENS. The balloons are equipped with radar and are tethered to concrete pads four-miles apart and designed to float at 10,000 feet. They are unmanned.

The test will last three years and one balloon will continuously scan 360 degrees from New York to North Carolina and as far west as Ohio.

The other carries precision radar to hep the military on the ground the pinpoint targets. The balloons don't have weapons and would guide weapons launched from the air, sea or ground toward incoming enemy missiles.