Integration of Satellite Based Broadband Data Service into the UH

Integration of Satellite Based Broadband
Data Service into the UH-60 Blackhawk
Sean Gannon
SAIC, St. Louis MO
[email protected]
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David J. Kinney
Project Lead, Aviation Applied Technology Directorate, Ft. Eustis VA
d avid.k inney @ us . army.mil
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ABSTRACT
Airborne Battle Command systems in the US Army require constantly increasing data communications bandwidth
in order to maintain connectivity with other mobile and fixed Battle Command systems. Database exchanges,
sensor data transmission, and Situational Awareness communications have created a need for mobile broadband
data connectivity that has outstripped the capabilities of traditional military communications systems. Additionally,
communications systems that have performed this function in the past have been terrestrially based, which limits
their geographic coverage and requires substantial resources in-theater in order to operate effectively. Airborne
Battle Command platforms such as the UH-60 Blackhawk hosted Army Airborne Command and Control System
(A2C2S) therefore require Satellite based broadband data service in order to retain the efficacy of their embedded
Battle Command Software Systems in environments where terrestrially based communications systems are not
available. Challenges to integrating this capability into the UH-60 are signal blockage from the airframe, limited
locations for antennas, radiation hazards to personnel, and weight/space/power limitations. Under the direction of
the Project Management Office for A2C2S, the Aviation Applied Technology Directorate at Ft. Eustis, VA has
developed a suite of equipment for the UH-60 that provides a secure satellite based transmission facility with
bandwidth sufficient to carry multiple voice, video or data channels simultaneously. The final configuration
provides the user with a rapidly installed kit that provides these services in all operational environments and with
minimal impact to the weight, space, and power constraints of the host platform.
INTRODUCTION
Airborne Battle Command systems are becoming
increasingly dependent on high bandwidth data
communications in order to maintain situational
awareness, direct forces, and receive intelligence.
The most advanced of these, the A2C2S, has 8 onboard computer systems that require continuous
networked communications with other Battle
Command systems.
The A2C2S architecture has been primarily
dependent on the Near Term Digital Radio (NTDR) for
network connectivity with other Battle Command
systems. The NTDR was developed to bridge the gap
between the current need for tactical wireless
networking and the fielding of the Joint Tactical Radio
System (JTRS) and its Wideband Networking
Waveform. Both the NTDR and the JTRS are
terrestrially based communications systems which
require Line Of Sight (LOS) between terminals in
Presented at the American Helicopter Society 61st
Annual Forum, Grapevine, TX, June 1-3, 2005.
Copyright © 2005 by the American Helicopter Society
International, Inc. All rights reserved.
order to complete a circuit. During thousands of
hours of operation in Iraq, the A2C2S commonly lost
connectivity with the NTDR network due to range
limitations or terrain blockage. It quickly became clear
that a terrestrially based network such as the NTDR
or its replacement in JTRS is not a practical solution
for rapidly moving mobile platforms such as the
A2C2S in environments where forces are widely
dispersed.
The Program Management Office for A2C2S in
conjunction with the User Proponent decided that a
satellite based communications replacement for the
NTDR was required. An initial requirement was set to
provide 128 Kbps data service to the A2C2S without a
dependence on a terrestrial network.
This
requirement is approximately equal to the realized
data bandwidth of a NTDR radio in a tactical
environment. A growth requirement was also set to
permit up to 500 Kbps with minimal modifications to
the aircraft hardware as new satellite services
become available. The Aviation Applied Technology
Directorate (AATD) was selected by the PMO A2C2S
for development, performance testing, and rapid
prototyping of a system that meets these
requirements.
BACKGROUND
Master
Operator
A2C2S Description
The A2C2S provides an airborne Battle Command
platform for missions ranging from homeland security
to deep operations in high intensity conflict. To
accomplish this, the system must provide extensive
robust communications capabilities, situational
awareness, and computer systems, and must enable
the commander and his staff to rapidly traverse battle
space to critical places at critical times.
Fire
Support
Intel
Commander
Operations
The standard A2C2S communications suite includes
UHF Satellite Communications (SATCOM) Voice and
Data, UHF-AM, Havequick I/II, SINCGARS, VHF-FM,
EPLRS, HF w/ Automatic Link Establishment, and
Blue Force Tracking-Aviation (BFT-A).
An additional 11 antennas are required to support the
A2C2S mission kit (Figures 1 & 2), bringing the total
number of antennas on the host UH-60 to 23.
SINCGARS 2
SINCGARS 1
SATCOM/GPS
BFT-Aviation
Figure 1. A2C2S Antennas (Upper)
EPLRS
SINCGARS 3
SINCGARS 4
HQ 2
NTDR
HQ 2
Figure 2. A2C2S Antennas (Lower)
The commander’s environment (Figure 3) includes 5
user workstations, supporting Army Battle Command
Systems, BFT-A client, and other mission profile
software. The commander and his staff, through the
A2C2S, are able to see, understand, act, and finish
decisively while rapidly traversing the battle space.
The A2C2S began Rapid Deployment fielding with 3
systems in 2002 to support Operation Iraqi Freedom
and continues with Low Rate Initial Production in
2005.
Figure 3. A2C2S Maneuver
Commander’s Environment
Available Aviation Satellite Services
Satellite service options considered for meeting the
broadband requirement included Department Of
Defense operated communications networks as well
as commercially operated networks. Only networks
that are supported by currently available airborne
antennas and terminals were considered. Table 1
details each of the services considered.
System
Military /
Commercial
RF
Band
Bandwidth
/ channel
UFO
Iridium
Inmarsat
Swift 64
Inmarsat
BGAN
Boeing
Connexion
Military
Commercial
Commercial
UHF
L
L
56 Kbps
10 Kbps
64 Kbps
Commercial
L
432 Kbps
Commercial
Ku
5 Mbps
(down) 256
Kbps (up)
Table 1. Satellite Service Options
The UHF Follow On (UFO) system, which has been in
operation for over a decade, was designed specifically
for mobile users and works well on helicopters. The
terminals are relatively small and lightweight and
require only a simple omni-directional antenna.
Unfortunately, simultaneous operation of multiple
channels on the aircraft would require multiple sets of
equipment, and therefore growth to 500 Kbps is
impractical.
Additionally, the UFO network is
oversubscribed which makes it difficult to obtain
access to the system.
The Iridium system operates only narrowband
channels which were developed primarily for voice
communications. When these channels are adapted
to data communications, the data bandwidth is not
adequate to support A2C2S requirements.
The Inmarsat Swift 64 service is a popular choice for
many military and commercial aviation users. The
airborne terminals are capable of accessing up to 4
channels simultaneously which delivers up to 256
Kbps of bandwidth. When the Broadband Global
Area Network (BGAN) service becomes available in
2006, these terminals can be easily modified to
access BGAN services which will increase data
bandwidth to 432 Kbps per channel.
decrypt information. The satellite communications
network consists of the Inmarsat I3 constellation and
the Land Earth Stations which bridge the
communications into the Terrestrial network. The
Terrestrial network consists of the Public Switched
Telephone Network (PSTN). Lastly, the Tactical
Network Interface takes the communications from the
Terrestrial network, processes the same functions as
were performed in the aircraft, and then connects into
the Army’s Tactical Internet.
Connexion by Boeing offers by far the highest
available data bandwidth for aviation users.
Unfortunately, the airborne antennas and terminals
are intended for Boeing 737 and larger fixed wing
aircraft, and therefore are generally too large and
heavy for integration onto helicopters.
It was decided that operation in the L-Band spectrum
offered the best compromise between available
bandwidth and practicality of integration onto the UH60. Inmarsat was the only service offered in the LBand spectrum that could meet both the current and
future bandwidth requirements.
Inmarsat Description
Inmarsat is a privately held company which operates
a global satellite system comprised of its second and
third generation satellites.
The current system
supports voice and data communications to mobile
users in the maritime, aeronautical and land mobile
markets. Inmarsat’s Swift-64 service is designed
primarily for the airborne user. This service is
provided by the Inmarsat-3 (I3) Satellites. With 2
channels in operation the Swift-64 service is capable
of meeting the near term A2C2S broadband
requirement.
The Inmarsat BGAN service is aimed at delivering
multi-media services to personal, mobile and portable
terminal users. The BGAN service with data
compression and network acceleration will easily
meet the growth requirement of 500 Kbps.
SYSTEM COMPONENTS
Inmarsat System Architecture
The Inmarsat system architecture (Figure 4) consists
of an airborne element within the A2C2S, a satellite
communications network provided by Inmarsat, a
terrestrial data network, and a Tactical Network
Interface.
The airborne element consists of all mobile equipment
required to receive and transmit with the satellite,
process data, multiplex audio channels, and encrypt/
Figure 4. Inmarsat Architecture
Airborne Element Architecture
The airborne element is comprised of several basic
hardware groups (Figure 5). All of this equipment is
located on the aircraft. The Inmarsat Terminal
Assembly receives and transmits via the antenna and
does all signal processing such as channel
assignments, subscribing to the Inmarsat service, and
providing Integrated Services Digital Network (ISDN)
connections to the Networking Subsystem.
The
Autonomous Steering Unit continuously updates the
Inmarsat Terminal with the location, altitude, roll, pitch
and yaw data of the aircraft in order to keep the
antenna pointed at the satellite. The equipment
selected for the Inmarsat Terminal Equipment
Subsystem consists of an EMS HSD-128 Terminal,
LITEF Aircraft Heading Reference System, flux valve
compass, and a GPS/ WAAS Receiver.
The Networking Subsystem consists of all equipment
required to interface the ISDN connections provided
by the Inmarsat Terminal Subsystem to the A2C2S
mission kit. These functions include multiplexing
voice and data, network acceleration, data
encryption/decryption, and media conversion. The
multiplexing device allows dynamic allocation of the
available data bandwidth to either voice or data
functions.
There are 4 telephone connections
available for the user which can be used for either
secure or non-secure telephone calls. The network
acceleration device uses features such as
compression, application acceleration, and traffic
discovery to improve the apparent bandwidth of the
Satcom network.
the antenna elements. These antennas are generally
heavier than the mechanically steered types and also
require a larger surface area on the aircraft to mount.
Figure 6. Mechanically Steered Inmarsat Antenna
Figure 5. Airborne Element Architecture
Aircraft Antenna Selection
Figure 7. Electronically Steered Inmarsat Antenna
All Inmarsat antennas must be approved by Inmarsat
before being sold to end users for integration into
aircraft. Inmarsat ensures that the antennas have
sufficient gain, beam width, and can operate in the
temperature and vibration extremes of an aircraft.
The selection of an Inmarsat Antenna for A2C2S
therefore does not so much depend on the
operational characteristics of the device but rather on
the weight, space, and ease of integration of the
device.
From a performance point of view, these two types of
antennas generally have similar electromagnetic
characteristics when steered near the zenith. When
steered near the horizon, however, the electronically
steered antennas have a diminishing aperture and
lower antenna gain numbers. The mechanically
steered antennas maintain the same electromagnetic
characteristics regardless of which direction they are
pointed.
There are two basic types of Inmarsat antennas for
aircraft; mechanically steered (Figure 6), and
electronically steered (Figure 7). The mechanically
steered antennas are gimbaled in 2 axes and are
physically pointed at the satellite by an Antenna
Control Unit. These antennas are mounted inside an
enclosure called a Radome which protects the
antenna from the environment but is transparent to
the radio signals. In order for the antenna to maintain
LOS to the satellite while being mechanically steered,
it must protrude from the Outer Mold Line (OML) of
the aircraft.
The electronically steered antennas are generally
preferred for fast moving fixed wing aircraft since they
minimally change the OML of the aircraft.
To
compensate for off axis performance, often two of
these antennas are installed on either sides of the
aircraft. This ensures that one antenna is able to link
with the satellite without requiring high off axis angles.
With 23 antennas already installed, the A2C2S has
minimal available “real estate” remaining, and it was
decided to use a mechanically steered antenna which
would have a much smaller footprint than the
electronically steered antenna.
The electronically steered antennas, instead of being
physically steered toward the satellite, are
electronically reconfigured so that the main beam of
the antenna is shaped in the direction of the satellite.
These antennas do not have any moving parts and
generally do not stick out above the OML of the
aircraft by more than a few inches. They come with
an integral outer cover which forms the radome over
The AMT-50 mechanically steered antenna from EMS
Technologies in Ottawa Canada was selected by the
design team.
The AMT-50 already had been
successfully integrated onto the CH-53 and the CH-47
helicopters. EMS was also able to offer an off the
shelf radome for the AMT-50 which could be easily
adapted to the UH-60. These factors significantly
reduced program risk.
Tactical Network Interface (Ground)
The Tactical Network Interface forms the other end of
the communications link. It mirrors the equipment in
the A2C2S Networking Subsystem. ISDN lines come
in from the terrestrial service provider and are
processed identically as is done in the aircraft
Networking subsystem. The Ground Node is located
near an existing Tactical Internet processing facility.
AIRCRAFT INTEGRATION
Antenna Location Options
With the system architecture and major electronics
components defined, the most challenging issue
became where to place the AMT-50 antenna on the
A2C2S equipped UH-60.
The location for a SATCOM antenna on an aircraft
must provide a clear LOS between the antenna and
the Satellite. With geosynchronous (also referred to
as geostationary) satellites, the satellite remains fixed
above a given point on the earth. As the earth rotates
on its axis, the satellite orbits above the earth at the
same rate. Geosynchronous satellites are therefore
very popular for fixed base communications systems
because the ground antenna can be pointed to a fixed
position and then left alone. On an aircraft, however,
the antenna must constantly adjust to compensate for
changes in the aircraft’s attitude and to maintain the
correct bearing to the satellite as the aircraft moves
over the earth.
The ideal location for a SATCOM antenna on an
aircraft would be a location that provides a horizon to
horizon unobstructed view of the sky even as the
aircraft moves over its full range of roll and pitch
angles. SATCOM antennas are commonly installed
on fixed wing aircraft in either the top of the fuselage
or on the top of the vertical stabilizer. In these
locations, the path between the Inmarsat antenna and
the satellite is rarely obstructed by the airframe. In
helicopters, however, the main rotor system limits the
number of locations for a SATCOM antenna.
Locating equipment above the main rotor system as is
done in the OH-58D and AH-64D is complex and
expensive. The only practical locations on a rotorcraft
therefore suffer from some blockage from the airframe
and main rotor system.
An initial list of candidate locations was generated
based and an evaluation performed on the integration
feasibility of each. The locations and Pros / Cons for
each is detailed in Table 2.
Of these 7 candidate locations, 3 were considered
low-risk and also did not interfere with existing UH-60
and/or A2C2S systems: the External Stores Support
System (ESSS) Wing, the Forward Avionics Bay Door
(Nose), and the Engine Access Door. Only these
three locations would be further evaluated as possible
locations for the Inmarsat Antenna.
Candidate
Location
Top of
Vertical
Stabilizer
Above Main
Rotor
Forward
Maintenance
Access Door
APU Access
Door
ESSS Wing
(Wing)
Airframe impact, Integration
complexity, and Programmatic
Considerations
↓ Structure not robust enough
↓ High Vibration Environment
↓ High cost
↓ Lengthy development schedule
↓ High Technical Risk
↓ Interference with operation of
Wire Strike Protection System
↓ Cable wear when operating door.
↓ Blocks Infrared Countermeasures
system
↓ Potential Electromagnetic
Interference with GPS Receiver
and ATC/IFF Transponder
↓ Location crowded with other
antennas
↑ Requires minor modifications to
aircraft
↑ Low development cost and risk
↓ Forces ESSS configuration at all
times
↑ Existing Weather Radar Location
↑ Low development cost and risk
Forward
Avionics Bay
Door (Nose)
Engine
↑ Requires minor modifications to
Access Door
aircraft
(Engine)
↓ Potential structural issues
Table 2. Initial List of Candidate Locations for
Inmarsat Antenna & Pros/Cons
Performance Analysis of Antenna Locations
An analysis was conducted on the three acceptable
antenna locations to quantify the expected
performance of the Inmarsat system at each. The
analysis had two primary purposes; 1) determine the
amount of airframe Blockage for each location, and
2) determine the Radiation Hazards to Humans for
each location.
The airframe blockage analysis assumes that the
Inmarsat Antenna will operate properly when it has a
visual Line of Sight to the Satellite. This is considered
a worst case assumption since with diffraction of the
Electromagnetic Wave there would be more of a
gradual attenuation of the radio signal as the antenna
moved into the shadow of the airframe rather than an
abrupt interruption of the signal. With this worst case
assumption, a high degree of confidence is built into
the analysis that if visual LOS is maintained between
the antenna and the satellite, the Inmarsat Link will be
maintained.
In order to perform the LOS blockage analysis, the
aircraft was simplified into 3 rectangular shapes; main
rotor system, upper fuselage, and main fuselage. For
each antenna location a geometric analysis was
performed to determine the azimuth and elevation
angles at which LOS blockage occurred (Figures 8, 9,
& 10).
12 &13). These are areas where personnel should
be restricted during ground use of the Inmarsat
system.
Figure 11. Radiation Hazard Region Wing Mounted Antenna
Figure 8. Geometric Analysis of Airframe
Blockage to Wing Mounted Antenna
Figure 12. Radiation Hazard Region Nose Mounted Antenna
Figure 9. Geometric Analysis of Airframe
Blockage to Nose Mounted Antenna
Figure 13. Radiation Hazard Region Engine Door Mounted Antenna
Figure 10. Geometric Analysis of Airframe
Blockage to Engine Door Mounted Antenna
Radiation hazard analysis was performed by plotting
areas in and around the aircraft where the Inmarsat
antenna could point and where the radiation field
strength level exceeded the FCC limit for controlled
exposure. If any of these plotted areas coincide with
an operator location within the A2C2S (red shaded
areas in Figures 11, 12 & 13), then software
modifications would need to be made to the Inmarsat
terminal in order to inhibit transmitting while the
antenna is pointed into these areas.
Inhibiting
transmitting while in these regions effectively creates
another blocked region, further limiting the
performance of the Inmarsat system.
Radiation
hazard areas for areas outside the aircraft are also
plotted (areas marked with solid red line in Figures 11,
The LOS blockage and the Radiation Inhibit region
must be then overlaid on top of each other to
determine the overall effective blockage for a
particular antenna location.
The effective blockage (actual plus radiation inhibit)
only impacts the operation of the system if the
antenna actually needs to steer into the blocked
region to maintain link with the satellite. In order to
determine if this will occur, the elevation angle to the
satellite for each geographic location must be
determined. Since the geosynchronous satellite stays
fixed above a point on the earth along the equator,
there is one geographic location on the earth where a
particular satellite is directly overhead.
Moving
radially away from that location, the SATCOM
antenna must point to decreasing elevation angles in
order to remain pointing at the satellite. Eventually
the angle to the satellite goes below the horizon.
Since the I3 satellite constellation consists of 4
spacecraft, it is rare that an angle above the horizon
of less than about 10 degrees is required.
Since the A2C2S is being equipped for operation in
specific locations around the world it seemed
appropriate to predict the blockage for those specific
locations rather than generically for worldwide
operation.
There were 7 locations selected for the analysis
where A2C2S aircraft were expected to operate in the
next few years: Ft. Drum, NY; National Training
Center, CA; Joint Readiness Training Center, LA;
Germany; Korea; Kuwait; and Northern Iraq (Mosul).
While operations in any part of Iraq are possible, the
Northern and Southern extremes of Mosul to Kuwait
provide a reasonable range of Satellite elevations with
which to predict system performance. Germany and
Korea were modeled at the approximate geographic
center of each country.
The critical factor for determining blockage is the
elevation angle to the satellite. The closer the satellite
is to the horizon, the more likely that the airframe will
cause blockage. For all antenna locations, blockage
is possible only for a range of aircraft azimuth
bearings (i.e. when the main rotor mast or other
airframe component is between the antenna and the
satellite). For this reason, the actual azimuth location
of the satellite is ignored and the analysis plots
azimuth bearings relative to the front of the aircraft.
Since the blockage is a function of the antenna angle
relative to the aircraft rather than to the earth, a
baseline aircraft attitude, and a dynamic range of
aircraft attitudes needed to be selected. The baseline
attitude adjusts the elevation angle relative to the
earth to an angle relative to the aircraft. These
numbers would be typical for straight and level flight
for the aircraft in an A2C2S configuration. The
baseline roll attitude selected is 0 degrees. The
baseline pitch attitude selected is -3 degrees for
ESSS wings installed and -1 degree without ESSS.
Since elevation angles to the satellite are the driving
factor towards operational performance, yaw attitude
is ignored as it has no impact on antenna elevation
angle.
The dynamic range of aircraft attitudes is selected to
approximate the range of attitudes expected from a
UH-60 performing a Battle Command mission. The
roll range variation is +/- 15 degrees, and the pitch
range variation is +/- 5 degrees. These angles are
represented as vertical arrows (Figures 14, 15, & 16)
to show variation in blockage as a result of dynamic
flight. Since the nose mount antenna location is on
the center butt line of the aircraft, changes in the roll
angle of the aircraft have minimal effect and are
ignored. Also, since the engine door and ESSS wing
locations are approximately along the same
longitudinal station as the main rotor mast, changes in
pitch angle have minimal effect and are ignored for
those locations.
Summary of Blockage Analysis
The blockage analysis reveals that all locations suffer
from some blockage due to the airframe. The wing
location has blockage from the upper fuselage and
the main rotor mast (Figure14). In level flight, the
upper fuselage presents the most significant blockage
(100 degrees wide in azimuth) and impacts
performance in Korea, Germany, and NTC. Since
the analysis has the antenna on the left ESSS wing,
the blockage increases during 15 degree left turns
enough that the Mosul, Ft. Drum, and JRTC locations
would have reduced system performance. During 15
degree right turns there is no antenna blockage.
The nose location has substantial blockage from the
main fuselage due to the relatively low waterline
location of the antenna (Figure 15). In level flight all
geographic locations except for Kuwait have a 120
degree wide blockage. Changes in aircraft pitch
angle do not materially impact the overall
performance.
The engine door location has only minor blockage due
to the main rotor mast (Figure 16). This blockage is
45 degrees wide in azimuth and impacts performance
for Ft. Drum, JRTC, Korea, Germany, and NTC.
Since the analysis has the antenna on the left engine
door, the blockage increases during 15 degree left
turns enough that the Mosul, Korea, and Germany
locations would have reduced system performance.
During 15 degree right turns there is only minimal
blockage from the main rotor mast for Korea,
Germany, and NTC.
Figure 14. Wing Mounted Antenna
Blockage and Radhaz Regions
approximately 10 degrees above the angle where
airframe blockage occurs.
The inhibiting of
transmissions in this region substantially adds to the
blockage due to the airframe.
Due to the relatively high waterline of the engine door
antenna location, there is no radiation hazard region
for occupants of the aircraft. At this location, the
AMT-50 antenna is not capable of illuminating into
either the cockpit or the main cabin.
All three locations present a radiation hazard region
outside of the aircraft and proper procedures would
need to be followed to ensure personnel safety while
operating the Inmarsat system on the ground.
Figure 15. Nose Mounted Antenna
Blockage and Radhaz Regions
Selection of Antenna Location
Based on the results of the blockage analysis,
radiation
hazards
analysis,
and
operational
constraints, the engine door location was selected for
test, evaluation, and initial fielding. This location
offers good performance in the primary theater of
operation and does not require any mitigation of
Radiation Hazards. Additionally, this location places
minimal restrictions on the platform or tactics of
employment since the system can be operated with or
without ESSS wings installed.
Initial structural analysis of the engine access door
concluded that the materials and mounting method for
the door system is adequate to secure the AMT-50
antenna, associated electronics, and the radome.
CONCLUSION
Figure 16. Engine Door Mounted Antenna
Blockage and Radhaz Regions
Summary of Radiation Hazards Analysis
At the wing location, the radiation hazard region
occurs in the cockpit for the co-pilot and in the main
cabin for A2C2S operators at the two left
workstations. The left gunner position is inside the
radiation hazard region but is shielded by the wing
structure. The cockpit and main cabin radiation
hazards do require transmit to be inhibited but do not
dramatically change the system performance since
the radiation hazard regions occur at such low
elevation angles.
At the nose location, the radiation hazard region
extends well into the cockpit of the aircraft. In order to
ensure safe electromagnetic field levels, transmitting
of the Inmarsat system would need to be inhibited
The Inmarsat design developed by AATD allows the
A2C2S to un-tether from terrestrial data networks
while meeting the user’s requirements for broadband
data connectivity. Program risk was reduced by
performing quantitative analysis of possible antenna
locations to predict overall system performance on the
A2C2S/UH-60 platform.
A prototype of this system will undergo testing on an
A2C2S aircraft in March and April of 2005. If test
results confirm the analysis, then 11 A2C2S aircraft
will be equipped with this Inmarsat design in calendar
year 2005.
The design presented can be easily modified to
support the Inmarsat BGAN service which will
increase data bandwidth by more than triple. With
BGAN, this system is expected to meet the
requirements of the A2C2S well into the future.
ACKNOWLEDGEMENTS
The technical work presented in this paper was
performed by and funded by the Aviation Applied
Technology Directorate. SAIC’s role in this effort is
limited to the professional services provided under
contract DAAH10-02-F-007. The U.S. Government is
authorized to reproduce and distribute reprints for
Government purposes notwithstanding any copyright
notation hereon.