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A tethered balloon is a balloon that is restrained by a cable attached to the ground or a vehicle and so cannot float freely. The tether is attached to a winch which is used to raise and lower the balloon.
Tethered balloons have been used for a variety of purposes, including:
- Observation balloons
- Barrage balloons
- Advertising and other graphical displays
- Instrumentation or communications equipment platforms, for civil or military use
- Recreational flights
A tethered balloon may take any of three basic forms:
- An elongated (airship- or blimp-shaped) balloon with fins at one end to stabilise it so that it always points into the wind.
- A simple round balloon, without stabilisation.
- A hybrid tethered balloon or kytoon uses a combination of aerostatic buoyancy and aerodynamic lift similar to a kite.
Designed by Albert Caquot, French engineer, in 1914, the barrage balloons of World War I and World War II were early examples of tethered balloons. Military observation balloons were also used extensively in World War I. These early types used hydrogen as their lifting gas.
Today, tethered balloons are used for lifting cameras, radio antennas, electro-optical sensors, radio-relay equipment and advertising banners - often for long durations. Tethered balloons are also used for position marking and bird control work. Typically, they use the non-flammable gas helium to provide lift.
During the project of the Preliminary Evaluation of Air Quality in Cyprus, a tethered balloon from the University of Stuttgart was used in Nicosia and Limassol, in 2003.The results concerning this part of the project are given in the report published in the Air Quality in Cyprus.
A tethered balloon was made in France at Chantilly Castle in 1994 by Aerophile SA and following the installation of a balloon in Paris in 1999 the company has installed more than 60 tethered balloons in 25 countries. Aerophile SA is claimed to be the largest operator of tethered balloons in the world with six operations, Paris, Disneyland Paris in France and Orange County Great Park (CA), Walt Disney World (FL), Wonderworks Pigeon Forge (TN) and San Diego Zoo Safari Park (CA) in the US.
A helium balloon was tethered at Montecasino in South Africa next to the Bird Gardens. The ride took passengers up to approximately 120m above Fourways. On 21 November 2014 while performing a safety check in high wind, the balloon hit a nearby structure and detached from the passenger basket and moorings. One person was injured, but no fatalities occurred during the incident. 
The United States Geological Survey uses tethered balloons to carry equipment to places where conventional aircraft cannot go, such as above an erupting volcano. Tethered balloons are ideal as they can easily remain more or less in one place, are less likely to be damaged by volcanic ash, and are less expensive to operate than a helicopter.
Tethered balloons can be used as temporary transmitters, instead of a radio mast, either by using the tether which holds the balloon as the antenna, or by carrying antennas on the balloon fed by a fiber optic or radio frequency cable contained inside the tether. The advantage of tethered balloons is that great antenna heights are easily realizable and they can stay aloft for months.
Tethered balloons are sometimes used for advertisement, either by lifting advertisement signs, or by using a balloon with advertisements on it. Often both methods are combined. It is not uncommon to use specially designed balloons. By suspending a light source within the envelope, the balloon can be made to glow at night, drawing attention to its message.
Military and security aviation
During the 1990 Invasion of Kuwait, the first indication of the Iraqi ground advance was from a radar-equipped tethered balloon that detected Iraqi armor and air assets moving south. Surveillance tethered balloons were used in the 2004 American occupation of Iraq. They utilized a high-tech optics system to detect and observe enemies from miles away. They have been used to over watch foot patrols and convoys in Baghdad, Afghanistan and several other contingency operations.
The US Drug Enforcement Administration has contracted with Lockheed Martin to operate a series of radar-equipped tethered balloons to detect low-flying aircraft attempting to enter the United States. A total of twelve tethered balloons, called Tethered Aerostat Radar System, are positioned approximately 350 miles apart, from California to Florida to Puerto Rico, providing unbroken radar coverage along the entire southern border of the US.
The U.S. Army has developed a tethered aerostat to perform operational testing at Aberdeen Proving Ground beginning in 2015. The system, called JLENS, uses two moored balloons designed to provide over-the-horizon missile defense capability.
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List of manufacturers
- Aerophile SA
- Aerostat based communications and surveillance
- Air-Foil Aerostat
- Lindstrand Technologies
- Lockheed Martin PTDS Aerostat ISR system
- Raven Aerostar
- SkyDoc Aerostat resources
- Top I Vision
- Vigilance Rapid Deployable Aerostat
- Worldwide Aeros Corp
- "GAO-13-81, DEFENSE ACQUISITIONS: Future Aerostat and Airship Investment Decisions Drive Oversight and Coordination Needs" (PDF). Retrieved 2013-06-15.
- "Monte Casino hot air balloon explodes". eNCA. 21 November 2014.
- "Montecasino balloon breaks free". The Citizen. 21 November 2014.
- "Persian Gulf States - Kuwait - Regional and National Security Considerations". Countrystudies.us. Retrieved 2013-06-15.
- "Tethered Aerostat Radar System - United States Nuclear Forces". Fas.org. Retrieved 2013-06-15.