By John Keller

ARLINGTON, Va. - Officials of the U.S. Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., are moving ahead with a plan to develop a high-altitude surveillance airship with a structure that integrates several different sensor systems.

The program is called Integrated Sensor is Structure, otherwise known as ISIS, which envisions a stratospheric airship operating as a surveillance platform more than 43 miles above the Earth.

The goal of the ISIS program is to develop a stratospheric airship-based autonomous unmanned sensor with years of persistence in surveillance and tracking of air and ground targets.

DARPA officials say the ISIS airship will have the ability to track the most advanced cruise missiles from as far away as 370 miles, and enemy foot soldiers nearly 200 miles away.

DARPA, through the U.S. Air Force Research Laboratory in Rome, N.Y., awarded a $15.5 million contract in May to the Northrop Grumman Corp. Space and Missiles Group in Redondo Beach, Calif., to design and build the ISIS surveillance airship.

Northrop Grumman Space and Missiles also is working under terms of a $6.7 million contract to develop a direct-current efficient transceiver to minimize the prime power requirement of large-aperture phased array radar. The contract also calls for engineers to develop a low-cost, low-mass-module packaging solution to reduce the overall system weight.

The Northrop Grumman Electronic Sensors and System Section at Linthicum Heights, Md., has an $8.7 million contract to develop a lightweight, low-power density Active Electronically Scanned Array (AESA) technology for the ISIS. The technology will be dual-band (UHF and X-Band) and bonded to the flexible hull material of the airship.

Most recently, the Lockheed Martin Corp. Maritime Systems and Sensors segment in Akron, Ohio, won a $10.3 million contract in early June to perform preliminary design, analysis, development, production, and validation testing of an advanced hull material for the future ISIS airship.

Lockheed Martin experts will also find a way to adhere solar panels and radar arrays to the airship hull materials. Awarding this latest contract were officials of the U.S. Air Force Research Laboratory in Rome, N.Y., on behalf of DARPA.

The ISIS concept uses large apertures instead of high power to meet radar performance requirements. This approach makes the most of the airship’s size, and conforms to the platform’s limitations on weight and power.

Major technical challenges are the development of ultra-lightweight antennas, antenna calibration technologies, power systems, station keeping approaches, and airships that support extremely large antennas.