Israel started initial setup and testing this week of a new balloon equipped with a sensor it seeks to use for detection and early warning of cruise missiles and other threats.

The process started by beginning inflation of the new High Availability Aerostat System (HAAS) equipped with an Elevated Sensor (ES) in northern Israel at unspecified Israel Missile Defense Organization (IMDO) facilities, the U.S. Missile Defense Agency (MDA) said Nov. 3.

An aerostat is the name for an aircraft that gains lift via buoyant gas, like a balloon or airship.

MDA said this step was taken after years of development and manufacturing, with IMDA and the Israeli Air Force and industry operations. According to the U.S. Defense Department, HAAS will be one of the largest aerostats in the world.

The overall ES system consists of the HAAS with a radar that is designed to detect incoming threats “at longer ranges when operating at high latitudes,” MDA said.

“It will provide additional detection and early warning capabilities to the existing operational air defense detection array deployed around the State of Israel,” the agency added.

The ES radar system was developed under a cooperative program between the IMDO and MDA.

“During recent months, in several flight test campaigns, we have demonstrated Israel’s Multi-Tier Missile Defense Array’s outstanding capabilities against advanced threats including Cruise Missiles,” IMDO director Moshe Patel said in a statement.

“This aerostat system will cruise at high altitude and provide an exceptional multi-directional detection capability against advanced threats including cruise missiles,” he continued.

MDA Director Vice Adm. Jon Hill said the Elevated Sensor “is another great example of cooperation between the Missile Defense Agency, IMDO, and industry partners. The co-developed technology and research is a benefit to both nations.”

In a Center for Strategic and International Studies article brief published in September, Wes Rumbaugh and Tom Karako wrote about the utility of basing sensors on elevated platforms, like aerostats to cover a greater range.

“If a target is flying at a 300-foot altitude, for instance, a sensor 10 feet off the ground would have a range of about 25 nautical miles. A sensor in a tethered aerostat 10,000 feet off the ground would have a range of 144 nautical miles, and a high-altitude aircraft operating at 60,000 feet would have a range of about 323 nautical miles.”

“Extending the horizon is particularly critical for cruise missile defense, countering unmanned aerial systems (UASs), and hypersonic defense. Unlike ballistic missiles, cruise missiles travel at lower altitudes and on unpredictable flight paths, which may be outside the field of view of terrestrial sensors…Elevated sensors increase the engagement area by adding sensor coverage beyond the line of sight of terrestrial radars and by looking out, or down, over other terrain features that could obscure cruise missiles or small UASs from view,” the brief continued.

A Congressional Budget Office (CBO) report published last February analyzing national cruise missile defense issues for the U.S. said aerostats deployed to 10,000 feet would have about a 165-mile detection range. However, the report said such a defense for the entire contiguous U.S. could cost upward of $75 billion to $180 billion and could be cost prohibitive if covering more than a limited area.

The report said these aerostats “would provide at most 18 minutes of warning before a generic subsonic [Land Attack Cruise Missile] would reach the coast. That short warning time would be insufficient to provide a defensive layer of fighter aircraft.”

While the CBO report focused on issues of defense of the U.S. mainland, Israel is considerably smaller, somewhat larger than New Jersey.

In the CBO analysis of various cruise missile defense architectures, the report said an aerostat radar option could require Surface-to-Air-Missile defense sites acting like point defenses spaced about 12 miles apart to provide a 15-minute reaction time. 

“The inability to support a fighter layer and the extremely high cost under all but very optimistic assumptions about BMS reaction times suggest that Architecture 3 would not be practical for the defense of wide areas. Aerostats are better suited to support point defenses or the defense of small areas because the ability to concentrate shooters in a smaller area reduces the need for long warning times,” the report said.