Subject: [NEXTEL-1] Aerostat-Borne systems for defence and homeland security

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Date: Sun, 27 Oct 2002 15:01:02 -0500

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Aerostat-Borne systems for defence and homeland security

Source: Military Technology

Publication date: 2002-08-01

Arrival time: 2002-10-27

In recent times, the missions of airborne early warning,
surveillance and intelligence gathering has come to centre stage
with respect to a wide variety of defence and homeland security
needs. Within the range of possible solutions, aerostat-borne
systems are gaining recognition as high-performance, low-cost
packages that would provide attractive solutions.

The 71M Aerostat Test Balloon is shown here being prepared for
lift-off from the Aerostat Test Bed at McGregor Range, N.M in June
1996 during Exercise "Roving Sand". The Aerostat's radar system,
located in the gondola, was able to track aircraft and cruise
missiles at a range of up to 150nm. The 71 M project was part of the
R&D activities which have led to the JLENS programme. (US DoD /
Airman Benjamin Andera)

In order to place the considerations that will be expressed in
this article in their proper context, it should be appreciated that
although the aerostat serves as a unique platform for the above-
mentioned solutions, it is not the key element in an aerostat-borne
array. The electronic systems installed onboard the aerostat are
much more sophisticated and costly, and the various integration
tasks are by far more critical to the end mission. However, the
single most important element is the concept developed for each
application, which translates to the way information is processed,
handled and used.

The Need

Many countries are confronted with problems of detection and
early warning of potential hostile acts of various kinds. While a
nation's sovereignty should be defended in the air, on land and at
sea, air sovereignty has the highest importance due to the high and
sudden threat it can impose. Air threats such as small and low-
flying aircraft at long ranges are extremely difficult to detect.
Ground based defence arrays lack over-the-horizon detection
capability, yielding an extremely short alarm and reaction time, if
at all. Thus, the protection of a nation's airspace calls for the
ability to obtain timely and accurate data of all activities that
might develop to a threat situation. At the same time, land and sea
sovereignty calls for proper border and maritime surveillance
missions to be fulfilled. Recently, homeland security has joined
with the need for early detection and warning aimed to defeat
possible act of mass terror.

Surveillance, detection and early warning is achieved through
defence networks comprising a variety of sensors and electronic
systems, which are able to collect different types of information.
This might include various types of radar, electronic monitoring
equipment (ELINT), communication intelligence equipment (COMINT),
and observation systems. A single sensor or several integrated
sensors may be utilised. These data-gathering electronic systems can
be installed on various platforms, including land installations,
airborne, shipboard, or even stationed in space.

The TARS (Tethered Aerostat Radar System) is deployed along the
US Southern border, with the primary mission of providing support to
federal agencies involved in drug interdiction efforts. (Photo:
NORAD)

Each such platform has its advantages and drawbacks. Ground
installations for example, might be simple but suffer a major
disadvantage of having a limited coverage of range and altitude,
which results in limited data and short alert time. Space platforms,
on the other hand, are much more expensive but still limited to
glimpses of the arena due to the earth's rotation, and are usually
reserved to the great powers.

Recently another platform, the aerostat, has gained increasing
interest. Aerostat platforms, a newly engineered old concept,
represent a very attractive alternative platform, providing many
inherent advantages and possibilities. Aerostat platforms have
outstanding detection ranges and airspace coverage as well as long
mission duration capability, and offer low acquisition and operating
costs.

Aerostat - A Unique Platform

For the purpose of this article, aerostats are defined as
unmanned, aerodynamically shaped blimps that are buoyed aloft while
tethered to the ground by a single cable. There are several
categories of aerostats, which vary in size, lifting capacity, and
floating altitude. Typical sizes are in the range of 15-30m length,
with the large ones at 60-70m.

Aerostats comprise several unique elements and technologies,
including most notably the envelope, the tethering cable, and the
mooring system. The envelope is made of lightweight, multi-layered,
composite fabrics based on Dacron, Mylar, or Tedlar. These fabrics
are resistant to environmental degradation, minimise helium leakage,
and provide structural strength to the aerostat. The envelope is
filled with a non-flammable inert gas (typically helium) that
provides the lifting force, while ensuring the safety of the
platform.

The size of an aerostat, thus the volume of helium its envelope
contains, determines its total lifting capacity (this is also
dependent on the floating altitude and temperature). The total
lifting capacity equals the sum of three main loads: the envelope,
the tether, and the payload of electronic sensors. Therefore, it is
the engineering goal to minimize the self-weight of the envelope and
tether, through the use of advanced concepts and materials, to allow
maximum payload weight capacity.

The tether is a single, multipurpose cable stretching between the
aerostat and the ground. It serves to tether the aerostat firmly to
a mooring system, supplies the primary electrical power to the
airborne systems, and also contains a wideband fibre-optic link to
relay the data between the aerostat and the ground station.

The uniqueness of the aerostat as a platform, comes from its many
advantages, including:

- Detection Range & Coverage: An aerostat hovering at 15,000ft
(some 4,500m) offers a coverage range of more than 480km, and the
capability to detect and track small, low-flying aircraft and moving
surface targets;

- Availability/Mission Duration: Aerostats have long endurance
and provide virtually continuous operation at low cost. Airborne
time is generally limited only by the weather and routine
maintenance downtime;

- Data Collection Over Time: The continuous operation enables to
accumulate information over time, which serves as the basis for
intelligence and data base build up;

- Low Operating & Maintenance Costs: Aerostats provide continuous
coverage at a very low operation and maintenance cost, which are
calculated to be less than 5% of the figure for an aircraft
performing the same mission profile;

- Idea/ Environment for Electronic Sensors: Since aerostats have
excellent flight stability and a large hull, they provide an ideal
environment for all types of electronic systems and sensors;

- High Payload Capacity Large aerostat can lift payloads of more
than two tons;

- Survivability. Contrary to perceived myths, aerostat
survivability is actually very high, and equals all other sensors in
the battlefield (according to JLENS studies). Helium is a
nonexplosive, non-flammable gas, and the flexible and strong
envelope makes the aerostat surprisingly resistant to gunfire. When
holed, the gas seepage is very low, so the balloon does not fall out
of the air.

The JLENS (Joint Land Attack Cruise Missile Defence Elevated
Netted Sensor) is being developed for early detection, tracking and
engagement of low-flying cruise missiles and aircraft. (Photo: US
Army)

The operation control center of an aerostat-borne system: Built
up of unified situation awareness picture and control over response.
(Photo: Rafael)

Border and maritime surveillance: Observation is required for
target recognition and identification. (Photo: Rafael)

All these arguments make a compelling case for aerostats as an
optimal platform for defence and homeland security applications
dealing with surveillance, intelligence gathering and early warning.

Sensors

The aerostat serves only as a platform, a very good one as
discussed above, which carries advanced electronic sensors as
payloads. A variety of electronic systems, single or in combination,
would be mounted depending on the exact application. For a large
size aerostat, which usually will carry several systems, these will
represent the main cost drivers of the project.

The most common electronic systems to be installed on such
aerostats include:

- Radar: The prime sensor for most applications, which provides
low-cost wide-area surveillance. Radar types and characteristics
vary according to their mission ranging from airborne early warning
(AEW) to ground and maritime surveillance. Aerostat-borne early
warning radars are of the same type used for AEW aircraft such as
AWACS, and will support the build up of an air picture showing all
flying aircraft at ranges of hundreds of km. This allows for
identification of potential hostile activity, generate alarm, and
enable timely defensive action. In this case the radar may also
supports the task of controlling the airspace operation. Most
aerostat-mounted radars feature a rotating antenna, which is
contained in a windscreen compartment at the bottom of the hull.
However, future systems could employ electronically steerable beam;

- ELINT. Electronic monitoring equipment aimed to receive and
identify electronic emissions from adverse systems. This can include
for example the rec\eiving of radar emission, which may indicate a
potential hostile activity. Emission information gathered over time
will also serve to build up an intelligence database;

- COMINT: Communication intelligence equipment aimed to detect
radio and other communications links. This information might reveal
intentions, position, plans and tactics;

- Communications: Systems that are used for data distribution, as
part of the aerostat-borne array, or as a stand-alone application.
Standalone application may include relay stations, communication
between surveillance forces and intervention forces, and
applications requiring wide area coverage;

The Rafael Observation Baloon System (OBS) in operation. Notice
the transparent aerostat envelope for reduced visibility. (Photo:
Rafael

Detail of the radar installation in the gondola of the TARS.
(Photo: Lockheed Martin)

- Observation: Cameras and thermal imager systems, which are used
for surveillance tasks. Such systems may include day and night
capabilities, and will serve for recognition and positive
identification.

Operational Applications

The many advantages of an aerostat-home array, i.e. aerostat
platform with advanced electronic sensors, makes it highly suitable
for a number of operational applications that are briefly presented
below.

Airborne Early Warning

One of the main applications is airborne early warning systems,
which may include also the control over response operations as well
as intelligence gathering. The ability to generate a high-quality
air picture, which includes timely, full, and accurate data, is a
crucial element to obtain airspace dominance. Furthermore, AEW
provides an effective means to direct friendly fighters and air
defence missile batteries to counter enemy threats.

Early warning arrays have proven to be the key to successful
prosecution of both defensive and offensive air operations.
Traditionally ground installations provided the solution for this
task, however they lack the excellent coverage provided by airborne
solutions. For this reason, many nations are considering the use of
AEW systems based on a variety of aircraft platforms. Aerostat-
borne early warning system would carry many advantages in comparison
to conventional AEW aircraft. To start with, they provide continuous
operation at a very low operating cost, thus outperforming any other
airborne surveillance method providing the same mission profile. One
well-known example, still under development, is the US JLENS array.
The JLENS (Joint Land Attack Cruise Missiles Defence Elevated Netted
Sensors) mission, comprising of aerostat-home radars, is aimed at
early detection and tracking of low-flying missiles and aircraft, in
support of engagement by existing air defence systems.

Aerostat-borne early warning systems will normally be
complemented by fixed-wing solutions, which provide necessary added
value during conflict breakout or wartime.

Border & Maritime Surveillance

These military and para-military applications are aimed to
provide cost-effective solutions for wide area surveillance and
detection, in the protection of coastal and geopolitical boundaries.
Potential uses include monitoring sensitive border areas for
movement of potentially hostile forces, or counter illegal border
crossing for immigration or felony reasons. Maritime surveillance at
sea or along the coastline may be aimed to counter illegal
immigration, smuggling or piracy. Aerostat-borne systems, which
provide transparent borders, can also serve as a mean to establish
peace zone between previously hostile countries. For all these
applications, aerostat-borne surveillance system provides continuous
wide area coverage at a very low operating cost, and with fraction
of the manpower required by other methods performing the same
mission.

A typical aerostat configuration for border and maritime
surveillance will include radar, observation, and COMINT systems. A
longstanding example is the TARS (Tethered Aerostat Radar System)
which is deployed along the US Southern border. The TARS network
comprises eleven aerostat-home radars, with the primary mission of
providing support to federal agencies involved in drug interdiction
efforts. TARS radar data is provided to the US Coast Guard, US
Customs as well as to NORAD (North American Aerospace Defence
Command) for homeland defence mission.

Anti-Terrorism/Homeland Defence

Recently there is a growing attention and recognition of the high
potential of aerostatborne systems in the war against terrorism.
Aerostat-borne systems are now receiving thorough consideration, in
the US and elsewhere, as a critical supporting element that should
be introduced into homeland security networks aimed to defeat
possible act of mass terrorism such as the September 11 attacks. It
is only today, in the aftermath of these terror acts that a
comprehensive system solution is sought after, and this is where
aerostat-borne solutions comes to fit like glove-to-hand. Aerostat-
home systems would provide optimal solutions for the followin
aspects:

- Fill the gaps left in ground-based radar coverage, especially
in airpicture for air space under 5,000>ft, and reduce the need for
continuous use of airborne platforms like the AWACS;

A comparison of the respective performance of fixed-wing
platforms, JLENS and combination solutions for defence against land-
attack cruise missiles. This comparison remains of course valid for
most notional aerostat-borne systems. (Source: US Army)

- Extend radar coverage over outward directions that are not
covered by within-boundaries systems, getting advanced knowledge and
tracking of international flights. This will allow timely response
if needed:

- Build up of database over time to serve and refine future
instantaneous adaptive identification of non-routine, non-
conventional events. Such mission would be tackled optimally by the
long mission duration and low operating cost of aerostat-home
systems;

- Increased connectivity, coordination and collaboration between
surveillance authorities and response units. Aerostat control
centres will be particularly suitable for such connectivity between
early warning and control;

- Eliminate the need for wide-scale sorties of combat air patrol
fighters, air refueling tankers and surveillance aircraft, being
airborne 24 hours a day, seven days a week.

Working groups within the US, such as the inter-agency Homeland
Air Defence Working Group, have already identified the vast
potential of aerostat-home systems. In fact, according to publicly
released information, actions have already been taken to integrate
existing assets from the TARS and JLENS aerostat-home systems into a
newly formed nation-wide mode of operation, in coordination and
collaboration of both FAA and NORAD.

Other Applications

In addition to the above, aerostat platforms have other potential
military applications, some already in use and others planned for
the future. Such applications include military heavy lift of troops
and logistics, as well as special communication applications such as
VLF submarine communication, battlefield data links, wide area
cellular communication and Internet. Some of those applications will
use other balloon variants such as high altitude, stratospheric
airships, un-tethered and flying at altitudes of 70,Oft, well above
weather systems and commercial air traffic. Experiments and tests
have also been carried out for the possible use of aerostat
platforms in the framework of humanitarian demining operations.

System Integration - The Main Aspect

Aerostat-home arrays are "systems-of-systems" by nature. They
include aerostat platforms, a variety of advanced electronic
systems, data processing and fusion, and command and control
operation centres. A wide spectrum of disciplines, technologies and
management are required to make such project from definition to
deployment. System design and high level integration are performed
under the following three categories:

The US Navy is studying a SeaBase Aerostat Information Link
(SAIL) project for a moored ocean buoy/aerostat link. This diagram
refers to a preliminary aero-hydrodynamic analysis as part of the
SAIL feasibility study. (Photo: US Navy)

RosAeroSystems of Russia, founded in 1997 as a subsidiary of the
AUGUR Aeronautical Centre, is a leading lighterthan-air manufacturer
and developer. Picture shows the models of the PUMA aerostat
(foreground), designed for AEW/surveillance and communications relay
mission, and the MD-900 Modular Airship for sea and coastline
patrol, as presented during the recent Farnborough Air Show. (Photo:
Monch archive / J. Poppelmann)

- Systems-to-Platform Integration: The integration of a multitude
of electronic systems on an aerostat platform calls for a fine
engineering, satisfying the equipment requirements under the
aerostat constrains. The critical issues are electro-magnetic
compatibility (EMC), and weight and power consumption. EMC design
should reduce or eliminate possible interferences between the
various devices. This is achieved through appropriate design of
systems parameters, spacing, orientation, shielding etc.;

- Data Fusion: Radar data is combined with surveillance data
obtained by other sensors to produce an integrated situation
awareness picture. Complex applications such as data fusion,
decision support, data base manipulation, and tracking of thousands
of targets in real time, are mandatory. This supports the formation
of a single unified picture to enable effective command and control
operations;

- Command & Control Operational Centres: The operation centres of
aerostat-borne systems are the heart of the matter. This is where
the total situation awareness picture is built up, and control over
reaction is handled through it. The control centre, which is the
single most important element influencing mission success, handles
the following functions: Control over the aerostat platform and the
electronic sensors in order to obtai\n optimal working conditions
and the best possible information; Data processing and data fusion
for the preparation of a high quality, unified situation picture;
and, Initiation and control of response operations.

What Does It Take

Putting together an aerostat-borne system calls for knowledge and
experience in a wide spectrum of technologies, system integration,
operation and management. Such knowledge and experience in
performing similar projects would prove critical for system
definition, system integration, and operational deployment.

Rafael, Israel Armament Development Authority Ltd., is a world
leader in the development and production of defence and weapon
systems. Rafael employs in-house know-how in key technologies to
provide cost-effective, state-of-the-art systems and solutions for
military and homeland security applications. With 4,600 employees
and annual sales of more than US$680 million, the company
established growing presence in the international market.

Rafael is also an aerostat systems house, offering cutting edge,
interdisciplinary multisensor solutions. Based on more than three
decades of experience in definition, design, production, integration
and operation, Rafael's aerostat-borne systems are operationally
first rate and cost effective.

Rafael, with its long-standing experience in aerostat systems,
offers its customers tailor made solutions. These solutions are
based on two mandatory and crucial capabilities: Technical dexterity
of high-level system integration, and concept development and
implementation.

Summary

Aerostat-borne systems, configured for surveillance, intelligence
gathering and early warning, can provide efficient solutions to
complex defence and homeland security needs. Such systems can be
effectively integrated with, and complement, other existing means.

Currently several countries are already using aerostat-borne
defence systems, among them are the US, UK, Canada, France, Italy,
Sweden, China, South Korea and Kuwait. Others are considering the
use of aerostat-borne systems for various applications, due to their
high performance and low cost characteristics.

Col. Nazi Nahum OF, Ret.) is the Head of Aerostatborne &
Intelligence Systems at RAFAEL. Sheike Marom is Marketing Manager
for the Directorate of Naval, Intelligence & EW systems at RAFAEL.
He served as an officer in the IDF Navy, and holds a B. Sc. degree
in Electronic Engineering and Master in Business Administration.

Copyright Moench Verlagsgesellschaft mbH Aug 2002

Publication date: 2002-08-01

© 2002, YellowBrix, Inc.

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