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TETHERED AEROSTAT RADAR SYSTEM

Mission
The Tethered Aerostat Radar System is a balloon-borne radar system. The primary aerostat mission is to provide low level radar surveillance data in support of federal agencies involved in the nation's drug interdiction program. Secondary mission is to provide North American Aerospace Defense Command with low level surveillance coverage for air sovereignty in the Florida Straights. One aerostat, located at Cudjoe Key, Fla., transmits TV Marti, which sends American television signals into Cuba for the Office of Cuba Broadcasting.

Features
The aerostat is a large fabric envelope filled with helium. It can rise up to 15,000 feet while tethered by a single cable, which has a maximum breaking strength of 26,000 pounds. Normal operating height is 12,000 feet mean sea level.

The current aerostat network consists of two sizes of aerostats (275,000 cubic feet and 420,000 cubic feet) and two varieties of radars. The average aerostat is about two times the size of the Goodyear Blimp, i.e., the 420,000 cubic foot, aerodynamically shaped balloon measures 208 feet long by 65 feet across the hull, with a tip-to-tip tail span of 100 feet.

The aerostat system lifts a 1,200 pound or larger payload to operating altitude for low-level radar coverage. The aerostat consists of four major parts or assemblies: the hull, the windscreen and radar platform, the airborne power generator, and the rigging and tether assembly.

The hull of the aerostat contains two parts separated by a gas tight fabric partition. The upper chamber is filled with helium and provides the aerostat's lifting capability. The lower chamber of the hull is a pressurized air compartment called a ballonet. A sophisticated subsystem maintains constant pressurization of the ballonet, which maintains the shape of the aerostat's hull at all altitudes. The hull is constructed of a lightweight polyurethane-coated or Tedlar fabric that weighs only eight ounces per yard. The fabric is resistant to environmental degradation, minimizes helium leakage, and provides structural strength to the aerostat. The windscreen compartment contains the radar and is pressurized by the ballonet. The airborne power generator consists of an airborne engine control unit that drives the generator, and a 100 gallon fuel tank. All systems are operated by the aerostat's telemetry link to start and stop the engine and its generator. Finally, the rigging consists of the flying suspension lines connected to the main tether and mooring suspension lines.

The radar data of the aerostat is available to NORAD Command and the U.S. Customs Service. In addition, this information is available to a blockhouse ground station below, where a flight controller, seated before banks of meters and television screens, monitors the balloon's performance. All radar data is transmitted to the ground station, then digitized and fed to the various control centers for display. Doppler weather radars are installed at all sites. The sites obtain up-to-date forecasts and weather warnings from the Air Force Weather Agency.

Operators launch the aerostat from a large circular launch pad containing a mooring system (fixed or mobile), depending on the type of aerostat. The mooring systems contain a large winch with 25,000 feet of tether cable. During the launch sequence, the power winch releases the tether until the aerostat reaches operational altitude. When the aerostat is lowered, it is secured to a mooring tower and a rail system. While moored, the aerostat weather vanes with the wind.

Airborne time is generally limited only by the weather (60% standard operational availability) and routine maintenance downtime, which is minimal. Since the aerostats are stable in all winds below 65 knots, the aerostat program provides low-cost, one of a kind radar coverage uniquely suited for its given mission. Notwithstanding weather, aerostat and equipment availability averages more than 98 percent system wide.

Background
The first aerostats were assigned to the United States Air Force in December 1980 at Cudjoe Key, Fla. with the original 250,000 CF aerostat. An additional site was constructed and operated by the USAF at Cape Canaveral, Fla. in 1983. This site was deactivated a few years later. During the 1980s, the U.S. Customs Service operated a network of aerostats to help counter illegal drug trafficking. Their first site was built at High Rock, Grand Bahamas Island, in 1984. The second site was built at Fort Huachuca, Ariz. in 1986. Prior to 1992, three agencies operated the TARS network to include the USAF, U.S. Customs Service and the U.S. Coast Guard. Congressional language in 1992 transferred management of the system to the Defense Department, with the Air Force as executive agent. Under Air Force management, through contract consolidation and system standardization, the operations and maintenance cost per site has been reduced approximately 50% from $6 million in Fiscal Year 1992 to the current rate of $2.8 million.

For security and safety reasons, the air space around USAF aerostat sites is restricted for a radius of at least two to three statute miles and an altitude up to 15,000 feet.

General Characteristics
Primary Function: Low-level radar aircraft detection.
Prime Contractor: The sites are currently operated and maintained under contract with Lockheed Martin Systems Management. ILC Dover and Tethered Communications L.P. manufacture the aerostat-envelopes. Lockheed Martin manufactures the radars.
Volume: 275,000 and 420,000 cubic feet.
Tether Length: 25,000 feet.
Payload Weight: 1,200-2,200 pounds.
Maximum Detection Range: 200 Nautical Miles.
Date Deployed: 1978.
Operational Sites: Yuma and Fort Huachuca, Ariz.; Deming, N.M.; Marfa, Eagle Pass, and Rio Grande City, Texas; Cudjoe Key, Fla.; and Lajas, Puerto Rico. Sites located at Morgan City, La. and Matagorda, Texas are in a cold storage configuration. Contract Management Office and logistics hub are located in Chesapeake Va. 

(Current as of January 2003)