Warplanes: Stationary UAVs


March 6, 2007: The larger UAVs are popular mainly for their persistence (the ability to stay in the air, over a particular area, for a long time.) Predator and Global Hawk can stay in the air for over 24 hours at a time. Controllers and observers, operating, via satellite link, from bases in the U.S., see that the video and radar images get passed on to the people that need them. But the military has found that "stationary UAVs" (helium filled aerostats or tall towers) not only do the job, but do it a lot cheaper (under $1000 an hour, mostly for maintenance, repairs and personnel to monitor the sensors.) Compare this to Predator, which costs $5,000 an hour to fly, and Global Hawk, which costs $25,000 an hour. Global Hawk is so expensive partly because of the high end sensors used. Not everyone needs the high flying Global Hawk, or even a Predator. They just need a way to keep an eye on a large area (like a chunk of the Syrian, Iranian or Pakistani border) 24/7. JLENS and RAID are a much cheaper alternative, RAID have become popular alternatives to mobile UAVs.

Three years ago, U.S. Army sent 22 blimps (aerostats, actually) to Iraq and Afghanistan. The RAID (Rapid Aerostat Initial Deployment) blimps float at about a thousand feet up, tethered by a cable that provides power and communications to the day and night cameras up there. The big problem is ground fire from rifles and machine-guns. Iraqis, in particular, like using the RAID blimps as targets. Rifle fire won't destroy the blimps, but does cause them to be brought down more frequently for repairs. Normally, the blimps can stay up for 30 days at a time, but the bullet hole repairs have some of them coming down every few days. There are surveillance systems similar to RAID, but mounted on tall steel towers. These also suffer gunfire damage, but rarely any that damage the equipment.

The first army blimp went to Iraq in early 2004. That was one of its JLENS (Joint Land Attack Cruise Missile Defense Elevated Netted Sensor) systems, and its primary mission was to help defend offshore oil facilities from attack by terrorist speedboats. The JLENS system uses a 233 foot long, helium filled, unmanned blimp equipped with radar and other sensors. The JLENS blimp is about 2.5 times the size as the more familiar advertising blimp. Actually, the JLENS blimp is an aerostat, a blimp like vehicle designed to always turn into the wind and stay in the same place. The JLENS blimp is unpowered, and secured by a cable that can keep the aerostat in position at its maximum altitude of 15,000 feet. At that altitude, the JLENS aerostat can carry a two ton payload. The cable also supplies power, which means the blimp can stay up for about 30 days at a time before it has to be brought down for maintenance on its radars. Two radars are carried. One is a surveillance radar, the other is a precision track and illumination radar (PTIR). The surveillance radar provides long-range coverage (over 300 kilometers, exact range is secret), while the PTIR, which is a steerable system capable of tracking multiple targets, can focus in on items of interest.

JLENS equipment can also be mounted on a tower, but it is most effective when operating from the aerostat. JLENS can track low flying aircraft, as well as ships and ground vehicles. The system was originally designed to detect low flying cruise missiles, but off the coast of Iraq, it can detect hostile boats making a run for Iraqi oil facilities. JLENS has been used in Afghanistan. JLENS was still in development, and was recently approved for mass production. The original purpose of JLENS was to provide 24/7 coverage for approaching cruise missiles, as well as providing a communications relay for other radars and weapons systems (anti-aircraft missiles and warplanes) to coordinate detection and destruction of cruise missiles. Each JLENS system will cost over $200 million.

The RAID systems are much cheaper, less than five million dollars each, and the army has bought over fifty of them. RAID is used on aerostats as well as towers. The RAID aerostats operate an altitude of a thousand feet, which means its cameras can see out to about sixty kilometers. The smaller towers shorten that range quite a bit. The 30 foot tower can see out to eleven kilometers, the 60 foot tower out to 16 kilometers and 84 foot tower out to 20 kilometers. The 30 foot tower is adequate for most situations, which usually involve guarding a base.

The aerostats are operated by air defense troops, often from the reserves or National Guard.




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