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.