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Army revives old concept for modern mission

An airship that the Army says is the largest lighter-than-air vehicle ever used in U.S. military operations will make its debut flight in August as part of an effort to field a system to detect, track and shoot down cruise missiles.

Unlike ballistic missiles that typically fly a stable and predictable flight pattern, cruise missiles pose a challenge because of their ability to fly low and slow and change directions. The weapon systems now available for cruise missile defense, such as the Patriot and Terminal High Altitude Area Defense systems, rely on ground-based tracking radars that cannot see over the horizon and can be negated by ground obstacles such as mountains.

The Army wanted a better way to track cruise missiles and looked at using radar-equipped aerostats. The Army launched a program in December 2004 called the Joint Land Attack Cruise Missile Defense Elevated Netted Sensor, or JLENS, and contracted with Raytheon Integrated Defense Systems.

Raytheon is working to deliver two JLENS systems, each made up of two 74-meter-long helium-filled aerostats, a surveillance radar, a fire control radar, mobile mooring stations and communications packages. One of the aerostats hosts a surveillance radar, which provides 360-degree coverage, and the other carries a fire control radar, which receives the surveillance data and generates targeting data for Army weapons systems.

The aerostats will operate about 1½ miles above ground on tethers, providing the ability to detect and track cruise missiles as far as 200 kilometers away in every direction, said Lt. Col. Steve Willhelm, the JLENS program manager.

The systems are designed to operate continuously for 30 days, come down for eight hours of maintenance and go back up for another 30 days.

The first aerostat will make its first flight in August, Willhelm said.

In December, the aerostat will be transported to the Army’s Dugway Proving Ground, Utah, to be located with its surveillance radar. The second aerostat and its fire control radar will be matched up at Dugway in May. Testing of the two platforms will begin in September 2010, Willhelm said.

The first JLENS orbit will go through an entire lifetime of use during the Army’s test program, and the second is scheduled to be delivered to the first JLENS battery in September 2012, with initial operational capability envisioned for one year later. If the test program is successful, a decision on a production contract for 14 more JLENS orbits could be made in January 2012, Willhelm said.