1

Table of Contents

Sensors

Volume 7, Issue No. 2

5 Introduction: Sensors–Challenges and Solutions 

for the 21st Century 

Rear Admiral James J. Shannon

6 Introduction: Developing Innovative Solutions 

in Sensors Technology

Captain Sheila A. Patterson

7 Introduction: Providing Our Navy and Our Nation with 

the Best Electromagnetic Sensor System Solutions

Mrs. Virginia S. Hudson

Technology

8 An Innovative Radar Clutter Model

George LeFurjah

14 Affordable Common Radar Architecture (ACRA) Program

Stephen G. Thomas

20 Littoral Radio Frequency System Performance Forecasts

Robert E. Marshall

24 Infrared Sensor and Image Processing for the Chemical Agent 

Plume Tracking Capability

Dean Zabel

30 Digital Array Radar Test Bed

Ronnie A. Stapleton and Carlos G. Tua

38 Multifunction Electronic Warfare (MFEW) Technology 

Development Program

Janine Knott

42 Innovation Strategies for Undersea Sensing

Tom Choinski

Development

52 Dual-Band Radar Development: From Engineering Design 

to Production

Alan L. Tolley and John E. Ball

62 International Treaty Verification: Cobra Judy 

Replacement Program

Penny Moran and Chris Reasonover

68 Program Executive Office Integrated Warfare Systems 

Above Water Sensor Directorate Common Digital 

Sensor Architecture Design Initiatives

John Schofield

72 International Programs

Michael Madatic

76 Rapid Prototyping of Radar Signal Processing

David Leas

80 The AN/SPS-74 Periscope Detection Radar System

Ian Barford, Mark Tadder, and Christopher Gorby
2

Testing

84 Shipboard Testing of the SPY-1 Radar

Randy Strock

90 Integrated Electronic Warfare Test Facility

Mark W. Karrick and Ronald D. Wood

94 Dual-Band Radar Program: Government and Industry 

Teamwork Wins the Day

Brian Hill and David Scalia

Modernization

100 AN/SPY-1B/D Radar Design Changes Supporting Aegis 

Ballistic Missile Defense

Bernard Ulfers and George LeFurjah

106 The AN/SPS-48G Radar System Sustainability Upgrade

Daniel Quigley, Lance Walters, Caitlin McInnes, and Christopher Gorby

110 Technical Authority and the Future of Radar

Roger Kniceley

Table of Contents

(Continued)
3

Volume 7, Issue No. 2

Naval Sea Systems Command

Vice Admiral Kevin M. McCoy, Commander

Brian J. Persons, Executive Director

NAVSEA Warfare Centers

Rear Admiral James J. Shannon, Commander, NSWC

Rear Admiral Thomas G. Wears, Commander, NUWC

Mr. Donald F. McCormack, Technical Director, NUWC

Mr. Stephen E. Mitchell, Technical Director, NSWC

Naval Surface Warfare Center, Dahlgren Division

Captain Sheila A. Patterson, Commander

Stuart A. Koch, Technical Director (Acting)

Russell Coons, Corporate Communications Director

Margie Stevens, Coordinator

Patrice Waits, Editor & Layout

Clement Bryant, Layout Design & Graphic Artist

Brandy Anderson, Cover Design

Trey Hamlet, Graphic Artist/3-D Modeling

Electromagnetic & Sensor Systems

Virginia S. Hudson, Q Department Head

Ronnie Stapleton, Radar Systems Engineer

James Morrissett, Radar Systems Engineer

Steve Zehring, Senior Project Engineer

NSWC Dahlgren

John E. Ball Chris Reasonover

Mark W. Karrick Randy Strock

Roger Kniceley Stephen G. Thomas

Janine Knott Alan L. Tolley

David Leas Carlos Tua

George LeFurjah Bernard Ulfers

Michael Madatic Ronald D. Wood

Robert E. Marshall Dean Zabel

Penny Moran

NSWC Crane

John Schofield

NSWC Port Hueneme

Ian Barford Daniel Quigley

Christopher Gorby David Scalia

Brian Hill Mark Tadder

Caitlin McInnes Lance Walters

NUWC Newport

Tom Choinski

The Leading Edge Magazine is an official, authorized publication of the Naval 

Warfare Center Enterprise. The purpose of the publication is to showcase technical 

excellence across the Warfare Center Enterprise, and promote a broader awareness 

of the breadth and depth of knowledge and support available to the Navy and DoD 

at NSWC/NUWC.

Address all correspondence to Corporate Communications, C6

Email: dlgr_nswc_c6@navy.mil; or write to

Commander

Naval Surface Warfare Center, Dahlgren Division

Corporate Communications, C6

6149 Welsh Road, Suite 239 

Dahlgren, VA 22448-5130

NSWCDD/MP-09/32

Approved for public release; distribution is unlimited.
5

Rear Admiral James J. Shannon

Commander, NSWC

To engage an enemy, you first must be able to detect it. Consequently, all the firepower in the world won’t do our naval warfighters any good if they don’t know who or what to engage or where to 

fire. That’s what makes radars and other sensors so critically important. Moreover, these highly technical systems are needed for 

much more than detecting and engaging an adversary. They are also 

required for things such as controlling aircraft and missiles, maritime navigation, sensing abnormalities, and tracking the weather. 

Without these critically important systems, a captain’s eyes and ears 

would be lost at sea. 

I am extremely pleased to introduce this edition of The Leading 

Edge magazine, sponsored by the NAVSEA Warfare Centers. The 

theme for this edition is Sensors–Challenges and Solutions for the 

21st Century. Indeed, our Navy faces a great many challenges in 

the coming years. Enemy technological advancements require new 

countermeasures. New, more capable systems that are interoperable with joint and coalition systems will need to be designed, developed, and deployed, while older systems will need to be replaced. 

Littoral and riverine warfare require smaller and lighter sensors for 

the Navy’s smaller platforms.

The NAVSEA Warfare Centers welcome these challenges, because we’re in the business of providing solutions. We research, develop, test, and evaluate cutting-edge technologies and systems to 

equip the Navy with sensors on the sea, under the sea, in the air, 

and on the ground. It is a job that requires a tremendous amount 

of technical knowledge, as well as strong synergy among our joint 

warfighters, industry, and academic partners.

I invite you to read about the exciting and important work being accomplished by our Warfare Center scientists, engineers, technicians, and professional support personnel. Due to their tireless 

efforts and unwavering dedication, they are meeting our constitutional mandate to “provide and maintain a navy.” Readiness is our 

greatest challenge for the 21st century. Readiness is what we ultimately deliver!

Introduction

Sensors–Challenges and Solutions for the 21st Century
6

Introduction

Developing Innovative Solutions in Sensors Technology

Sensor systems have come a long way since early radar that centered on basic detection of ships and aircraft for self-protection. Application of sensor technology today spans all areas of theater. Well 

beyond detecting and tracking ships and submarines, sensors allow 

us to search for and locate mines, discern lethal environments, and 

track ballistic missiles. Thanks to expert analysis and engineering, 

sensor systems are providing accurate tracking at expanded ranges 

and are being utilized for a broad spectrum of applications. The result 

is better protection for our men and women in uniform.

From our involvement throughout the years with virtually every 

phase of development of the SPY-1 radar systems, to our application 

of open-architecture concepts across systems, NSWC Dahlgren has 

become a recognized leader in sensor systems integration. Together with our Warfare Center partners represented in the articles that 

follow, our team is applying state-of-the-art sensor technology and 

providing at-sea testing to support surface, air, and undersea Navy 

combat systems.

As ships’ designs change and systems become more complex, it 

becomes increasingly challenging to provide worldwide, high-quality, high-resolution, multiwavelength radar data. We face additional 

challenges as we face new terrorist threats and ever-changing combat scenarios. From infrared sensors and image processing used for 

tracking chemical agents, to air traffic control systems, our sensor engineering specialists are diligently working on ways to ensure safety 

both for the warfighter abroad and for citizens at home. 

The task of meeting these new challenges and upgrading aging 

shipboard electronic radar systems has been a continual challenge; 

but as you will read in this Sensors issue of The Leading Edge, our 

engineers and scientists have found robust solutions and effectively 

controlled costs. You will also gain a better understanding of the role 

the warfare centers play in addressing the needs of our warfighters.

I am proud to be Commander of one of the Navy’s premier research and development facilities for sensor technology and am confident that NSWCDD will continue its legacy as a leader in sensor 

systems integration and will meet the needs of the Navy and the nation in the 21st century.

Captain Sheila A. Patterson, USN

Commander, NSWCDD
7

Introduction

Providing Our Navy and Our Nation with the Best Electromagnetic Sensor System Solutions

Welcome to our Sensors issue of The Leading Edge. In the Electromagnetic and Sensor Systems Department at NSWC Dahlgren, 

Virginia, we are responsible for ensuring that the Navy’s surface ship 

and ground-based radars operate effectively in the operational electromagnetic environment. It’s a critically important responsibility 

necessary for providing naval warfighters with the tools they need to 

fight, win, and come home safely. It’s a responsibility that needs to be 

done right—right from the start.

With that responsibility in mind, I would like to take this opportunity to highlight the importance of warfighters involving 

electromagnetic systems engineers in fleshing out sensor system requirements—even before requirements are formally documented. 

That means warfighters and systems engineers working closely together to develop a common understanding of naval sensor problems and needs driven by operational requirements. It means helping 

warfighters translate their operational needs into formal, technical 

systems requirements to increase the likelihood that they will end up 

with effective sensor systems as a result of moving through the acquisition process. And it means supporting warfighter systems throughout the entire systems’ life cycle.

Working together with warfighters ensures that systems are engineered to work well together with other systems. That’s what systems engineering is all about. It’s not just about the operation of the 

systems working together in the laboratory environment, but also 

systems working together in the operational electromagnetic environment. Involving warfighters in the design, development, testing, 

and evaluation of sensor systems further increases the likelihood that 

their systems will interoperate with systems from the other services, 

coalition navies, and other departments and agencies, such as the Department of Homeland Security, the U.S. Coast Guard, and the Federal Aviation Administration.

Warfighters and systems engineers working together helps us 

better anticipate warfighter needs. So, while they are busy fighting 

wars and defending our nation, we can best serve their interests by 

continuing to explore more effective sensor capabilities, systems, and 

tactics to better arm them for current and future threats. In the end, 

working together, we provide our Navy and our nation with the very 

best technologies, systems, and solutions possible, while strengthening our country’s national security posture in the process.

Mrs. Virginia S. Hudson

Head, Electromagnetic and Sensor Systems

Department
8 Naval Sea Systems Command

Sensors

Technology

An Innovative Radar Clutter Model

By George LeFurjah

Engineers at the Naval Surface Warfare Center 

(NSWC) Dahlgren have pioneered a new method for modeling the complex environments that our Navy and Marine Corps face when operating radar systems throughout 

the world. The innovation involves combining radar clutter and atmospheric ducting models, including state-ofthe-art meteorological modeling. This is a groundbreaking 

effort—the first of its kind anywhere. The result is the Littoral Clutter Model (LCM). Although originally intended 

strictly as a model for shipboard radars, LCM has been extended to also apply to land-based radar applications. This 

article describes this new model and shows how it can be 

used to enhance Navy target detection, tracking, and discrimination capabilities in littoral environments.
9 NAVSEA Warfare Centers Volume 7, Issue No. 2

An Innovative Radar Clutter Model

layer, or the boundary between the water and the 

air, refracts the light, bending it such that the fish 

is on a different line to the eye than is apparent. 

If the person looks at a shallow enough angle, the 

surface no longer appears transparent, but rather it appears to be like a mirror. A similar refractive bending occurs in the atmosphere when the 

temperature, humidity, or air density forms layers. Under certain conditions, a layer above the 

radar can act as a partially reflective surface in 

which the pulse can be reflected back towards the 

surface, and by virtue of multiple reflections, the 

pulse can travel for great lengths along the surface. In the absence of such a condition, the pulse 

would travel in nearly a straight line and, because 

of the earth’s curvature, diverge from the surface. 

A depiction of the atmospheric boundary layer is 

shown in Figure 1.

Background — Complex 

Environments

There are two aspects to what is meant by environment: objects that are in the field of view of 

the radar and the atmospheric conditions that affect how those objects appear to the radar system. 

Radar operates by radiating electromagnetic energy from a focused antenna in the direction of 

some interesting targets; those targets are just a 

subset of the many objects in the radar’s field of 

view. That energy, typically in the form of short 

bursts or pulses, is concentrated by the antenna into a relatively narrow part of that field of 

view. When the energy is reflected from an object, it rebounds in the direction of the radar antenna and is then received and processed by the 

radar. Atmospheric conditions affect the path of 

that energy in two ways. Energy is absorbed by 

Boundary Layer

the atmosphere, and the path is altered by atmospheric refraction and, to a lesser degree, diffraction around intervening objects. The absorption 

process reduces the amount of reflected energy 

that the radar can receive, making it a little harder 

to detect the targets. Refraction is the more troublesome of the effects. Simple refraction changes the apparent direction of the targets. When the 

atmosphere is sufficiently layered in temperature 

or humidity, a refractive layer can act to bend the 

path down to where the energy reflects back and 

forth between the surface and the layer. An analogy of this effect is the optical refraction that occurs when a person looks at a fish underwater. The 

Because it is analogous to a waveguide, this 

condition is called atmospheric ducting, or simply ducting. This situation is not unique to radars. 

If you listen to radio in these conditions, you can 

sometimes pick up stations far away from your local area, sometimes hundreds of miles over the horizon from your location. The atmosphere does 

not have cut-and-dried simple layers, and the surface of the earth is not a flat, featureless plain. Thus, 

these complications make the prediction of how 

that path is altered a nontrivial exercise.

Clutter, simply put, represents targets that are 

of no interest to the radar’s mission, which is typically to detect and track moving air or ground 
10 Naval Sea Systems Command

Sensors

Technology

vehicles. Of course, one radar’s clutter might be 

another radar’s target. Weather radar, for example, 

tries to detect storm clouds and measure their velocity. Military radar would consider storm clouds 

to be clutter. Clutter is named for the appearance 

it presents on a typical radar display. Instead of 

simple target blips, the operator sees a scattered 

hash of signals. Some examples of clutter are rainstorms, sea surface scatter, land, trees, mountains, 

and buildings. Clutter has a number of undesirable effects on radar’s operation. It obscures targets by overpowering the target’s signal and is 

often simply a bigger target than a boat, aircraft, 

or missile. In other words, clutter reduces the ability to detect targets of interest. This is the probability of detection problem. The other key problem 

with clutter is that it can look like a target; it, too, 

can be detected and tracked. This is called the false 

alarm problem. When radar automatically detects 

and tracks targets, clutter can overload the system 

with false tracks. Once again, if it were weather radar, these storms tracks would not be false at all. 

Whatever the perspective as to what constitutes 

clutter, it is a problem for radar that must be acknowledged, accounted for, and dealt with.

When the atmosphere enhances propagation 

on the surface, then clutter—which is almost entirely a near surface phenomenon—can present returns from many miles, even hundreds of miles, 

away from the radar. This long-range and extended clutter is much more of a problem in both detection and false alarms. Figure 2 depicts recorded 

radar data from USS Lake Erie operating in the 

Persian Gulf. In this depiction, ducting conditions 

caused land clutter to be visible from hundreds of 

miles away. The radar is generating a picture of the 

whole shoreline of the Gulf, even inland in Iraq.

Littoral Radar Clutter Model

Coastal (or littoral) combat operations are the 

major drivers for current U.S. Navy radar system 

design. As we have seen, coping with clutter and 

atmospheric considerations is crucial to the task of 

providing adequate new radars. Consequently, adequate simulations of the environments faced by 

these new radars are crucial for radar system design and radar system performance analysis. In the 

current acquisition environment, adequate simulations are also a crucial adjunct to expensive, live 

system testing. When based upon complex spatially and temporally inhomogeneous atmospheric propagation prediction, realistic littoral clutter 

predictions are useful from all of these perspectives. When used in conjunction with radio frequency (RF) scene generation, these models can 

even replace some radar performance specification 

testing. All these considerations led to the development of LCM at NSWC Dahlgren.

LCM is a synthesis of several elementary models—a model of models (see Table 1). LCM models 

surface clutter from the land and the sea, while using up-to-date topographical data. It also models 

the atmosphere’s effect by modeling the refractive 

properties of the atmosphere and the propagation 

of the radar pulse through that atmosphere using 

a mathematical process called parabolic equation 

computation. NSWC Dahlgren pioneered the 

use of mesoscale numerical weather prediction 

(MSNWP) technology to generate a 3-D picture of 

the atmospheric refraction.

Figure 2. Map of Recorded Radar Data from the Persian Gulf with the Geographic Map of the Region
11 NAVSEA Warfare Centers Volume 7, Issue No. 2

An Innovative Radar Clutter Model

DTED Level 1 Terrain Data—to model Land Topography

AVHRR Global Land Cover Database—to model Land Surface Reflectivity Characteristics

Billingsley Empirical Land Clutter Model—for Land Radar Reflectivity (σ0

)

GTRI Sea Clutter Model—for Sea Surface Reflectivity (σ0

)

JHU/APL TEMPER Radar Propagation Model—to compute Propagation Factor (F4

)

COAMPS—Coupled Ocean/Atmosphere Mesoscale Prediction System to model the atmosphere

Table 1. Littoral Model Component Models

Component Model Descriptions

Input Data

Variable height, site-specific terrain, is computed with terrain contours from Digital Terrain 

Elevation Data (DTED) files provided by the National Geospatial-Intelligence Agency (NGA).

The United States Geological Survey (USGS) 

provides a global land cover database, Advanced 

Very High Resolution Radiometer (AVHRR), with 

24 terrain type classifications with a latitude and 

longitude worldwide reference. The terrain types 

are correlated with the DTED data to associate appropriate electrical properties and surface roughness values with each patch of terrain. Together, 

these data provide the terrain heights, electrical 

properties, and surface roughness for each clutter 

patch along each radar propagation path. In addition, they provide inputs for the computation of 

clutter reflectivity.

Surface Clutter Models

LCM is primarily a statistical model, meaning 

that the clutter is computed based upon known statistical variations rather than on precise modeling 

of every object that might be in the radar field of 

view; but the statistics are computed based upon 

the nature of the surface on the earth at specific locations. In order to model backscatter from patches of terrain or ocean surface, it is usually necessary 

to employ an empirical clutter model, rather than a 

conceptual or physics-based clutter model. This is 

especially true in the case of low-angle radar clutter, where this model applies. The empirical models 

employed provided, distributed clutter amplitude 

statistics, in terms of Weibull means and spreads, 

to represent the normalized clutter reflectivity, σ0

. 

The radar cross section of a patch of surface clutter is computed as σ0

 times the propagation factor, 

multiplied by the area of the clutter cell. The NavyStandard Georgia Tech Research Institute (GTRI) 

model provides σ0

 for sea clutter, and the low-angle radar empirical land clutter model designed by 

J. Barrie Billingsley at Massachusetts Institute of 

Technology (MIT) Lincoln Laboratory provides σ0

for land clutter.

The Billingsley land clutter model was chosen for very low-angle radar land clutter. It is 

based upon extensive land clutter measurements 

conducted by MIT Lincoln Laboratory of a large 

range of terrain types over a range of depression angles and surface slopes, for both vertical 

and horizontal polarization, and from very high 

frequency (VHF) to X-band, approximately 200 

MHz to 10 GHz.

Atmospheric Propagation Model

Parabolic equation computation provides a 

fast solution to Maxwell’s equations. Although 

the details of this process are beyond the scope 

of this article, this technique allows the modeling of the atmospheric propagation over a realistic, topographically complicated surface. The 

atmospheric refractivity may vary with respect 

to range and height. The surface boundary may 

be ocean or variable height terrain of range-varying composition. The Tropospheric Electromagnetic Parabolic Equation Routine (TEMPER) is a 

parabolic equation code that was developed at the 

Johns Hopkins University Applied Physics Laboratory (JHU/APL). It uses refractivity profiles, 

which are refractivity as a function of height and 

ground location, as well as surface roughness derived from surface land cover to compute radar 

propagation.
12 Naval Sea Systems Command

Sensors

Technology

Mesoscale Numerical Weather Prediction 

(MSNWP)

The weather reports we see on the news every night are predicated upon complex computer 

simulations of the atmosphere. These models cover 

very large areas of the earth and are called synoptic weather prediction models. MSNWP is a very 

similar process but computed for much smaller areas. To get an idea of the scope, synoptic models 

might cover thousands of miles; mesoscale models 

cover a few hundred. The idea of using MSNWP to 

generate realistic depictions of site-specific atmospheric conditions and combining them with sitespecific clutter is a unique development innovated 

at NSWC Dahlgren.

MSNWP is the numerical modeling of the 

physical/dynamical nonlinear differential equations 

that govern atmospheric flow. Initial conditions are 

developed by combining previous forecasts with 

new meteorological observations through a process 

termed data assimilation. Simultaneous numerical 

integration of these equations provides a prognostic capability out to 72 hours. MSNWP models are 

typically 100 × 100 km and nested within a global forecast model. The lateral boundary conditions 

for the MSNWP models are derived from the larger 

scale global model. MSNWP models employ horizontal grid resolutions sufficient to resolve circulations produced by local surface features, such as 

air/land/sea boundaries and topography. Advances in computing power allow for horizontal resolution as fine as 1  km. In order to provide this 

resolution over an area of interest, MSNWP models are multi-nested, with the resolution becoming 

finer from nested grid to the next nested grid. Resolving near-surface refractivity is one of the most 

challenging applications for MSNWP, where refractivity profiles are derived from the MSNWP model 

profiles of pressure, temperature, and humidity. Research and development classes of MSNWP models currently may provide 10 m vertical resolution 

in the first 100 m near the surface.

MSNWP currently provides a qualitative, 

four-dimensional—three spatial dimensions 

and time—refractivity field in the littorals. The 

MSNWP model will resolve the local circulation 

that produces the current anomalous propagation 

regime. The phase of the circulation, the height of 

the atmospheric boundary layer, the vertical gradients of temperature and water vapor, and the sea 

surface temperature will be slightly different from 

those measured by in situ meteorological instrumentation. This will result in some duct height and 

strength errors but will provide insight into the 

varying structure of coastal refractivity.

The Coupled Ocean/Atmosphere Mesoscale 

Prediction System (COAMPS) is the MSNWP 

model that has been chosen for use in LCM. It was 

developed by the Marine Meteorology Division of 

the Naval Research Laboratory (NRL) in Monterey, 

California.

Oil Rig Platform Clutter

Although the Billingsley statistical data (referenced in Table 1) does a good job of predicting 

the occasional large-amplitude return from land 

clutter, it will not predict the return from discrete 

objects that are permanently installed away from 

shore. The biggest of these in terms of reflecting radar energy are oil-drilling and ship-loading platforms. The Vector Vertical Obstruction Database 

(VVOD), developed and maintained by NGA, provides the locations of these oil rigs. By using this 

database and modeling the radar return from these 

rigs as analogous to a large ship, LCM has been 

modified to include a discrete clutter layer that reveals the radar return as an overlay on the basic 

LCM clutter picture. Figure 3 shows an example 

oil-drilling platform.

An Example Use of LCM

Figure 4 illustrates an example that shows the 

realistic portrayal of clutter possible with the LCM 

clutter simulation. For this example, the model 

was centered at the latitude and longitude coordinates of USS Lake Erie at the moment clutter was 

recorded. That data is shown in the Plan Position 

Indicator (PPI) display on the right side of the figure. The COAMPS weather prediction code was 

used to generate a prediction of the atmospheric 

conditions at the time of the data collection. The 

COAMPS data for this study were generated at the 

NSWC Dahlgren. As can be seen on the left side of 

the figure, the LCM-generated data is a very reasonable depiction of what was actually seen aboard 

ship. The shoreline, islands, inland mountains in 

Iran (to the top right of the PPIs) and the oil rigs 

are seen clearly in both pictures. Some of the details—such as low-level sea clutter near the ship—

are missing from the model. Currently, engineers 

and meteorologists at NSWC Dahlgren and NRL 

Monterey are working on improvements to the resolution of COAMPS near the surface, which hopefully, will increase the accuracy of model results 

even more.

As a result of these innovative radar-clutter 

modeling efforts, Navy warfighters in the future 

will be better armed with enhanced target detection, tracking, and discrimination capabilities in 

littoral environments.
13 NAVSEA Warfare Centers Volume 7, Issue No. 2

An Innovative Radar Clutter Model

Figure 3. An Example Oil Drilling Platform

Figure 4. Littoral Clutter Model Simulation of Clutter Seen Aboard USS Lake Erie

LCM with COAMPS

Clutter Data Recorded 

Aboard USS Lake Erie
14 Naval Sea Systems Command

Sensors

Technology

Affordable Common Radar Architecture 

(ACRA) Program

By Stephen G. Thomas

14 Naval Sea Systems Command

Sensors

Technology
15 NAVSEA Warfare Centers Volume 7, Issue No. 2

Affordable Common Radar

Architecture (ACRA) Program

Today, the Navy and Marine Corps are fielding a number of legacy surveillance radar systems that are 

approaching obsolescence. Despite efforts underway to address the modernization and refurbishment of 

some of these systems through the Radar Obsolescence, Availability Recovery program and other initiatives, 

many systems in the field today are quickly becoming unsupportable. Indeed, there is no Navy-wide coordinated effort to address surveillance radar obsolescence in the fleet, and there is currently no affordable, U.S.-

made radar with sufficient capability for shipboard long-range surveillance.

15 NAVSEA Warfare Centers Volume 7, Issue No. 2

Affordable Common Radar

Architecture (ACRA) Program
16 Naval Sea Systems Command

Sensors

Technology

Legacy surveillance radar systems approaching obsolescence include the AN/SPN-43, AN/

SPS-48E, TPS-59(v)3, AN/TPS-75, and AN/SPS49(V). They provide the fleet and the Marine 

Corps with a range of capabilities necessary for air 

traffic control and combat operations. Moreover, 

in addition to these systems approaching obsolescence, much of the current supply has been refurbished. Systems approaching obsolescence are 

shown in Figure 1.

In light of the need for timely and affordable 

system modernization across the board, the Office 

of Naval Research (ONR) initiated a Future Naval 

Capability (FNC)-funded program and tasked the 

Naval Surface Warfare Center, Dahlgren Division 

(NSWCDD) with oversight, technical direction, 

technology development, and integration. The Affordable Common Radar Architecture (ACRA) 

program, kicked off in FY09, is a risk-reduction effort with the goal of developing a scalable, common architecture with supporting technologies 

applicable to long-range surveillance radars. For 

the warfighter, ACRA represents improved performance in the littoral regions with a reliable, supportable, affordable system. The ACRA program 

will provide capability for both rotating phased arrays and multifaced fixed arrays based on a core 

group of common, scalable components. These 

Figure 1. Legacy Surveillance Radar Systems Approaching Obsolescence

Legacy Navy Surveillance Radar Systems

TPS-59(V)3

SPS-49A(V)1

SPN-43C

TPS-75 3D

SPS-48E
17 NAVSEA Warfare Centers Volume 7, Issue No. 2

Affordable Common Radar

Architecture (ACRA) Program

components include the radar array’s mechanical structure and electrical signal network, digital 

receivers, waveform generators, and data processor. Separate transmit (TX) and receive (RX) arrays flood a search region with a single, wide TX 

beam and multiple, digitally formed, simultaneous RX beams. The digital receivers are located on 

the array structure, while the beamforming and TX 

circuitry is located below decks. Figure 2 shows a 

conceptual drawing of these components.

The 5-year program plan calls for the design 

and construction of an affordable Advanced Development Model (ADM) risk-reduction, rotating radar prototype. Unlike many current radar 

systems, the ACRA radar will comprise two separate antenna structures—a TX array and an RX 

array—in contrast to a single, common TX/RX 

array. This has the potential to lower overall system cost through a number of innovative array 

design techniques currently being investigated 

by NSWCDD and the ACRA team. For example, a low-power, air-cooled RX array printed circuit board design and a small, passive TX array 

are currently undergoing cost and performance 

trade studies. In parallel with array development, 

NSWCDD is involved in technology development 

efforts aimed at producing cost-effective, scalable 

receivers; waveform generators; and signal processors based on an open-architecture specification developed by NSWCDD for the ONR Digital 

Array Radar (DAR) program. Once the array and 

technology risk-reduction and development efforts are completed, the entire system will be integrated into an ADM prototype for testing and 

demonstration in FY13. These ACRA system 

components will leverage DAR technologies and 

cost-saving concepts. ACRA system components 

are shown in Figure 3.

Figure 2. The ACRA System Concept
18 Naval Sea Systems Command

Sensors

Technology

The performance requirements for the ACRA 

system must span the requirements of multiple 

legacy systems. Indeed, the overarching goal and 

primary challenge facing the program is to design 

and build an affordable, scalable system capable of 

replacing multiple legacy systems. Chief among 

the requirements is the capability to accurately 

search a large volume at long range; to update this 

search at a sufficiently high rate to track objects of 

interest; to mitigate the effects of sea clutter and 

anomalous atmospheric conditions on radar performance; and to possess the capability to mitigate 

hostile jamming. Trade studies are underway to 

optimize the system architecture to demonstrate 

scalable system performance and system cost to 

meet the needs of various potential end users. For 

example, to effectively search a large volume (at 

long range) with a sufficient update rate requires 

a high-power TX antenna emitting a wide beam, 

coupled with a large RX antenna forming multiple, 

simultaneous RX beams. NSWCDD RX antenna trade studies are examining array architectures and their resulting patterns. Figure 4 shows 

the generation of a low sidelobe pattern based on 

a triangular element grid, further based on a staggered arrangement of circuit board panels. 

NSWCDD is also leading the way in defining 

the system architecture and subsystems requirements forming the backbone of the entire ACRA 

system. The subsystem technologies include digital 

receivers, waveform generators, reference clocks, 

and beamformers. The physical digital and analog interfaces between these subsystems are defined within an open-architecture design concept 

based on open, standard, nonproprietary protocols 

and signal formats, as initially developed and defined by ONR’s DAR program. The benefits of an 

open-architecture design are many, including subsystem development in a competitive environment 

to reduce system cost; the use of relatively inexpensive, readily available commercial products and 

standards; ease of hardware upgrade (technology 

refresh) during the life of the system; and ease of 

adding future functionality (technology insertion) 

once the system is deployed.

The Navy’s current fleet of shipboard longrange surveillance radars is approaching obsolescence. Moreover, future naval radar systems are 

Figure 3. ACRA System Components

Frequency Synthesizer

Frequency Down Converter

Digital Beamforming 

Circuit Board

Printed Circuit Board 

Antenna Array
19 NAVSEA Warfare Centers Volume 7, Issue No. 2

Affordable Common Radar

Architecture (ACRA) Program

expected to be largely digital in design. The ACRA 

program represents an opportunity for developing 

a new, modern, affordable, and scalable Navy radar asset based on a digital open-architecture concept. Over the next 5 years, NSWCDD scientists 

and engineers will be working to make this concept a reality. As a result, Navy and Marine Corps 

warfighters will experience improved performance 

in a reliable system for shipboard surveillance and 

combat support.

Figure 4. Low Sidelobe Pattern Based on a Triangular Element Grid, Further Based 

on a Staggered Arrangement of Circuit Board Panels
20 Naval Sea Systems Command

Sensors

Technology

Littoral Radio Frequency System 

Performance Forecasts

By Robert E. Marshall

Radio frequency (RF) propagation refers to the impact of the atmosphere on RF energy as it flows through the atmosphere between antennas. RF propagation is influenced 

by the clear atmosphere, rain, fog, cloud, snow, ice, and electron densities found in the 

ionosphere. Propagation in the clear atmosphere can significantly impact RF system 

performance. Refraction is the bending of light energy or RF energy. Refraction at optical wavelengths is observed when one inserts a pencil in a glass of water and the pencil 

appears bent at the top of the water column. The bending of light energy by small raindrops produces rainbows. You cannot see RF energy as it is bent in the clear atmosphere, 

but on a perfectly clear day with no visible clues from the atmosphere, radar may suffer 

severe refraction and subsequent poor mission performance. As RF energy leaves the 

antenna, it is bent by the atmosphere in ways that can easily refract it away from the intended target. RF energy is especially attracted to areas in the atmosphere with high humidity or low temperatures. Radar operators who do not account for refraction can be 

easily fooled by what the radar signal is telling them about targets.

Navy surface radars and communication systems operate in a shallow layer of the 

atmosphere called the marine atmospheric boundary layer (MABL). The MABL can 

extend from the sea surface up to as high as 1000 m—a complex environment where 

humidity, temperature, and refraction vary wildly. The MABL is drastically more complex within 100 km of the coast than it is over an open ocean. RF energy can be bent 

or refracted in various ways in the MABL. Figure 1 illustrates the four RF refraction 

categories.

Standard propagation or refraction has roots in the U.S. National Advisory Committee on Aeronautics (NACA) 1922 definition of a standard atmosphere. The NACA 

standard atmosphere was necessary to provide a standard for aircraft performance. 

Unfortunately, the standard atmosphere is more likely to be found above the MABL 

and typically provides a false impression of radar performance within the MABL. Super-refraction occurs when the RF energy is bent just enough such that it hugs the 

curvature of the earth. RF energy travels great distances in the MABL when it is superrefracted, allowing radars to see targets and communications systems to operate at abnormally long ranges. This propagation benefit is often complicated by the potential 

accompanying liability of folded land clutter and radio frequency interference (RFI). 

Subrefraction occurs when higher humidity is found at the top of the MABL, and RF 
21 NAVSEA Warfare Centers Volume 7, Issue No. 2

Littoral Radio Frequency System 

Performance Forecasts

energy rapidly bends away from the earth’s curvature. Subrefraction is a relatively rare event, but 

when subrefraction occurs, radar detection of targets in the MABL becomes significantly more difficult, and the naval surface platform becomes more 

vulnerable to an approaching target. Trapping or 

ducting occurs when higher temperatures are at 

the top of the MABL, and higher humidity is at the 

bottom of the MABL. The RF energy is trapped or 

ducted between the top and bottom of the MABL 

and bounces back and forth as it propagates away 

from and back to the antenna. Ducting develops 

radar holes or skip zones where targets cannot be 

detected, and it also produces areas of sea clutter, 

where targets are difficult to detect.

To make matters worse, the MABL is forever evolving, driven primarily by the land/sea temperature difference. During daylight hours, the 

sun heats the land much faster than the ocean often leading to a sea breeze, as the model in Figure 2 

demonstrates. Warm, dry air flows offshore at the 

top of the MABL, and cool, moist air flows onshore 

at the bottom of the MABL. After the sun sets, the 

circulation tends to reverse as a land breeze with 

warm, dry air flowing offshore near the sea surface and cool moist air flowing inshore aloft. As 

this typically 24-hr cycle progresses, the refractivity field in the MABL is constantly readjusting and 

constantly impacting RF system performance.

Accounting for these constantly varying refractive and propagation influences on RF system 

performance is essential for operations, acquisition engineering, and prototype RF system testing. The use of weather balloons, helicopters, 

rocket weather sounding systems, unmanned aerial vehicles (UAVs), and weather buoys have all 

been employed to document the refractive environment in the littorals. These are logistically difficult, expensive, and lack the ability to forecast 

what will happen in the future.

Figure 1. RF Propagation or Refraction Categories

Figure 2. Sea Breeze Circulation
22 Naval Sea Systems Command

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Technology

The Naval Surface Warfare Center, Dahlgren 

Division (NSWCDD) has a 15-year history of research and development in clear-air refraction of 

RF energy and how it impacts radar and communication system performance. For the last 5 years, 

NSWCDD has exploited the rapidly maturing technology of numerical weather prediction (NWP) 

to capture the four-dimensional (4-D) refractive 

structure of the MABL. NWP is displayed daily by 

television broadcast meteorologists as time-lapse 

forecasts of rainfall, clouds, or wind. This same 

NWP technology can be employed to forecast refractivity in the MABL. NWP models are globally locatable, provide a 48- to 72-hr forecast, and 

take into account all the land/sea characteristics 

that drive the evolving MABL refractive structure. 

There are dozens of NWP models used by military 

and civilian agencies around the world. NSWCDD 

runs the Coupled Ocean Atmosphere Mesoscale 

Prediction System (COAMPS). COAMPS is the 

U.S. Navy medium-scale NWP model developed 

and supported by the Marine Meteorology Division of the Naval Research Laboratory in Monterey, California (NRL-MRY). COAMPS products 

are run operationally by the Fleet Numerical Meteorology and Oceanography Center (FNMOC), also 

in Monterey, California, for many locations around 

the globe in support of fleet operations.

NSWCDD’s COAMPS system consists of two 

Linux clusters. The research and development cluster named Bean resides at NRL-MRY and supports 

COAMPS improvements by way of a scientific collaboration between NSWCDD and NRL. As these 

improvements are validated, they are ported to the 

operational cluster at NSWCDD named Dutton/

Mesos. Dutton/Mesos supports RF test beds at Wallops Island, Virginia, and the Potomac River Test 

Range (PRTR) at Dahlgren. Example COAMPS 

model output for both locations is shown in Figure 3. Figure 3 displays temperatures at 2 m above 

the surface and wind flags at 10 m above the surface. The 1-km horizontal resolution is indicated 

by the locations of the wind flags. Dutton/Mesos is 

also capable of simultaneously supporting models 

at four other global locations.

These same COAMPS models are capable of 

forecasting refractivity in the MABL. Thus, refractivity is provided every kilometer, every hour out to 

48 hr in the future through the depth of the MABL.

The refractivity fields by themselves are of little use to RF engineers until paired with modern 

RF system models. RF system performance models 

have been modified in recent years to accept NWP 

0- to 48-hr refractivity forecast fields. The coupled 

model pair can lead to 0- to 48-hr RF system performance forecasts as illustrated in Figure 4.

The Advanced Refractive Effects Prediction 

System (AREPS) is developed and supported by 

the Propagation Research Branch of the Space and 

Naval Warfare Systems Command (SPAWAR)/

San Diego. AREPS ingests COAMPS refractivity fields and specific RF system specifications, 

and computes system performance. Figure 5 is 

an example of a combined COAMPS/AREPS radar performance forecast for a notional S-band radar located along the edge of the Gulf Stream off 

the Eastern Shore of Virginia. The white radials 

along each bearing indicate the range at which a 

Figure 3. COAMPS Models Over Wallops Island (a) and the PRTR (b) (Wind flags at 10-m ASL and air 

temperatures at 2-m ASL are displayed.)
23 NAVSEA Warfare Centers Volume 7, Issue No. 2

Littoral Radio Frequency System 

Performance Forecasts

notional target 10 m above the surface is detected 

by the notional S-band radar. The variation in detection range with bearing is indicative of how the 

refractivity field can vary in the MABL. The red 

ring indicates the detection range in a standard atmosphere. The reduced detection ranges relative 

to a standard atmosphere indicate areas of subrefraction to the north of the ship. The extended detection ranges southwest of the ship are due to an 

area of super-refraction. These azimuth-dependent predictions of radar detection range are due 

primarily to the spatial changes in MABL structure as it reacts to the significant changes in sea 

surface temperature found along the edge of the 

Gulf Stream. All these atmosphere and sea surface 

impacts are captured by COAMPS.

Refraction—or the bending of RF energy—if 

not accounted for, can severely impact the performance of naval radar and communication systems 

operating in the MABL. These impacts influence 

operations, acquisition engineering, and prototype RF system testing. By combining modern 

numerical weather prediction models with RF system models, it is possible to create site- and timespecific littoral RF system performance forecasts. 

The current technology is qualitative but has been 

used NSWCDD to support RF acquisition engineers, prototype RF system 

test engineers, and operational decision-makers. A strong research effort 

at NSWCDD aims to make significant 

increases in littoral RF system performance forecast accuracy in the next 5 

years. This same NWP technology is 

being employed by NSWCDD to provide chemical agent transport and 

dispersion forecasts, and sound propagation forecasts. Each of these forecasting capabilities will help to ensure 

that warfighters are armed with effective capabilities and accurate information necessary to fight and win in the 

electromagnetic environment.

Figure 4. A Radar Performance Forecast Structure

Figure 5. COAMPS/AREPS Model of the Detection Range of a 

Notional Target 10 m Above the Surface by a Notional S-Band Radar: 

Range rings are drawn every 20 km. The red ring indicates the 

detection range in a standard atmosphere.
24 Naval Sea Systems Command

Sensors

Technology

Infrared Sensor and Image Processing for the 

Chemical Agent Plume Tracking Capability

By Dean Zabel

Chemical agents, when dispersed into the air, form plumes or clouds of particles that 

can impact warfighters and others in the immediate vicinity. Moreover, just as clouds in 

the sky form, move and dissipate, so do chemical agent plumes. Unlike clouds in the sky, 

however, chemical agent plumes might not be easily visible or detectable. Thus, warfighters could be exposed to chemical agents without knowing it, thereby endangering 

their lives and missions. Consequently, a means to test the capabilities of developmental 

chemical agent detection systems was needed to ensure that those systems provide the 

promised protection when deployed. The Chemical Agent Plume Tracking Capability 

(CAPTC), developed at the Naval Surface Warfare Center (NSWC) Dahlgren, provided 

a way to track chemical agent plumes to provide that testing capability. 

CAPTC was designed to provide a referee capability for testing chemical-agent detection systems. A refereed capability refers to an unbiased measurement of the presence 

of a chemical-agent plume against which to compare the performance of the system 

under test. As such, the CAPTC operator will know at the start of a test which chemical is present in the plume. This permits the operator to configure CAPTC optimally 

for a particular simulant chemical agent release. The visual display provided by CAPTC 

also serves as a tool to assist the test director in conducting system tests. CAPTC employs near real-time tracking of chemical agent plumes using infrared (IR) images of the 

plume’s location and extent, as determined from two or three locations.

Previous IR Camera Testing

Earlier testing using IR cameras was performed with the Joint Service Lightweight 

Standoff Chemical Agent Detector (JSLSCAD). Those tests demonstrated the need for 

very sensitive long-wave infrared (LWIR) cameras to provide near real-time plume 

tracking.1

 During those tests, it was found that the vapor plumes of a chemical agent 

simulant provided a low contrast to the ambient scene. This then required a significant 

amount of posttest processing time to make the plumes detectable. In order to provide 

near real-time imagery, very high-speed processing of the IR video was found to be required. This article overviews CAPTC, its IR camera requirements, and the software integration and architecture needed to make the system work. 
25 NAVSEA Warfare Centers Volume 7, Issue No. 2

Infrared Sensor and Image Processing for 

Chemical Agent Plume Tracking Capability

The IR Camera Problem

The testing of chemical agent plumes must be 

carried out using simulants since actual chemical 

agents cannot be used. Because of their nature, the 

simulant plumes of interest to CAPTC are difficult 

to detect with an IR camera. The simulant is entrained as an aerosol in a high-velocity, high-volume flow of ambient air. Thus, the aerosol plume 

has very little temperature difference from the surrounding air into which it is injected. The mission of the chemical agent detector is to detect low 

concentrations of chemical agents. Thus, the content of the plume is not greatly different from the 

surrounding air mass against which it is to be detected. The requirement to be able to track the simulant plumes in near real time makes the problem 

even harder. 

The IR cameras used for the JSLSCAD tests 

were wideband microbolometers. Microbolometers generally have detection bands from about 

7.5  μ to 13.5  μ. This band more than covers the 

spectral characteristics of the simulants used in 

the JSLSCAD testing. However, microbolometers 

are not particularly sensitive. The microbolometers used for the JSLSCAD tests had minimum resolvable temperature differences (MRTD) of about 

0.1°K. When viewed live, subtle changes in the IR 

scene caused by the vapor plume could sometimes 

be detected by the camera operator, but not always.

The posttest image processing for JSLSCAD 

tests used frame averaging. Up to 15 video frames 

were averaged to enhance the plume sufficiently to ascertain its position and size. This process 

was very labor intensive and time-consuming. The 

IR video collected for JSLSCAD tests was at a low 

frame rate of 5 frames per second. This meant that 

frame-to-frame registration was difficult to accomplish because both the camera and the plume 

generator were moving. This low frame rate was selected to manage the storage requirements for the 

digital video data. In retrospect, it would have been 

better to record the camera’s maximum 60 frames 

per second digital video. An even higher frame 

would ease the frame-to-frame registration process. This became one of the factors driving selection of IR cameras for use in CAPTC.

Camera sensitivity becomes a limiting factor 

in how fast a frame rate may be utilized to collect 

enough photons to have a viewable image. As stated 

above, microbolometer technology is not very sensitive. To gain sensitivity, one needs to go to IR cameras that have cryogenically cooled detector arrays. 

Cooling the array and its associated readout electronics greatly reduces the sensor’s noise by decreasing random electron motion. Commercial cooled 

cameras have achieved MRTDs in the 0.025°K 

range. However, most cooled LWIR cameras do 

not have the full detection-band capability needed 

to detect the simulants of interest. One of the simulants, sulfur hexafluoride, has a single spectral feature at about 10.6 μ. Thus, a camera detection band 

out to at least 11 μ is required.

Cooled LWIR cameras tend to have detector 

arrays of two types: quantum well infrared photodetector (QWIP) and detector arrays made from 

mercury cadmium telluride (MCT). Both types 

can be very sensitive. QWIP cameras have spectral 

detection bands of about 7.7 μ to 9.2 μ. Most MCT 

cameras have a similar detection band, though 

MCT can be formulated for wider detection bands. 

Unfortunately, few typical applications require 

the wider detection band, making the wider band 

MCT arrays much more expensive. 

Spectral filtering also helps when the object to 

be detected exhibits emissive or absorptive spectral characteristics that are much narrower than 

the spectral response of the detector. Filtering 

helps by limiting the background to the spectral 

region of the object to be detected. The three simulants typically used in testing have different spectral characteristics such that a different filter would 

be optimum for each. This made it desirable to get 

a camera with an integrated filter wheel capable 

of holding at least four filters. The integrated filter 

wheel makes it possible to quickly select the optimum filter, or no filter at all, since CAPTC needs 

only three for each particular test run. The use of 

spectral filtering also drove the need for high camera sensitivity due to an increase in loss from the 

additional optical element.

The Camera Solution

An extensive search was performed to identify a commercially available IR camera to meet the 

needs of CAPTC. One MCT camera was located 

that had a detection band from 7.7 μ to 11.6 μ and 

included an integrated four-hole filter wheel. This 

was the CDIP Jade VLWIR. The Army’s West Desert Test Center at the Dugway Proving Ground, 

Utah, had also selected this camera for a similar 

application. Between the time of selection and time 

of purchase, the Jade VLWIR was updated to the 

Titanium SC7900. 

The Titanium is a very sensitive camera, with 

an MRTD < 0.025°K using a 320 horizontal × 256 

(240 displayed) vertical MCT array. It supports a 

frame rate of 90 frames per second for full frames, 

with on-the-fly selection of any of its four filter 

wheel holes. The control and video output interface is gigabit Ethernet. The Ethernet interface is 
26 Naval Sea Systems Command

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Technology

an improvement over the older RS-422 for digital 

video plus RS-232 for control used by the Jade. A 

software development kit was purchased with the 

camera to allow development of a control interface 

optimized for CAPTC. 

The spectral characteristics of each of the three 

simulants were used to determine an optimum filter to use for each simulant. The specifications of 

the filters were: 7.75 μ to 9.25 μ, 8.6 μ to 10.6 μ, and 

9.9 μ to 11.3 μ ±1% for each value.

The final piece of the IR camera is the optics. 

The JSLSCAD testing involved sensor-to-plume 

ranges of from 500 m to 6 km. The variation in 

ranges was needed to assess the sensitivity of the 

chemical agent detection system under test. Sometimes a plume release close (1.5 km) to the test 

system would be followed by one a long distance 

(5.5  km) away from the test system. Keeping the 

plume in the field of view and yet having sufficient 

resolution for the needed detail over this span of 

ranges dictated the use of multifocal optics. Quick 

physical access to the camera system would not be 

possible because the camera system needed to be 

environmentally protected from weather and RF 

emissions. Focusing and changing from near optics to far optics had to be accomplished quickly, 

so the optics needed to be remotely controllable. 

An appropriate commercial off-the-shelf multifocal lens had already been interfaced with the Titanium camera. The lens from StingRay Optics had 

triple field-of-view optics. It was fully controllable 

using a control box and 50-ft cable that came with 

the lens. The focal lengths were 75/150/300 mm, 

providing fields of view with the Titanium of 7.3° x 

5.5°/3.7° x 2.8°/1.8° x 1.4°, respectively. The Titanium camera integrated with the triple field-of-view 

lens is shown in Figure 1 with the mounting plate 

portion of its environmental enclosure.

Figure 2 depicts a sample of images acquired 

by the Titanium camera. Shown are emissions 

from one of the Morgantown power plant stacks in 

Maryland at a distance of approximately 2.5 nmi. 

The first image is a basic IR image. The second image utilized some of the image-processing capabilities of the Altair software purchased with the 

Titanium camera. The Altair software package provided the ability for a frame-to-frame differencing 

view, which was done by subtracting one camera 

frame from the next. The resulting image showed 

only what changed between the two frames. The 

Altair software provided great posttest analysis capabilities when supplemented by software developed at NSWC.

Test Environment and Basic Data 

Capture Architecture

The software developed at NSWC provided 

the integration of a number of test assets, ships, 

or platforms with data-collection equipment, and 

the equipment aboard each asset to facilitate the 

test data collection of a given test event. CAPTC, 

as a system, encompasses the data-collection 

equipment on all of the assets tied together by 

the software. A notional test situation that would 

Figure 1. Titanium Camera with the Stingray Optics on the Mounting Plate Part of 

Its Environmental Enclosure
27 NAVSEA Warfare Centers Volume 7, Issue No. 2

Infrared Sensor and Image Processing for 

Chemical Agent Plume Tracking Capability

utilize the CAPTC environment is depicted in 

Figure 3. Each test asset is installed with test datacapture equipment that stores all local data and 

data broadcast from other assets. As a simulant is 

dispersed by the Gatlin, a Naval Surface Warfare 

Center, Dahlgren Division (NSWCDD)-owned 

ship outfitted with a blower system is used to 

generate the simulant plume, the data-capture 

equipment tracks and records the location of each 

asset and the calculated position of the chemical 

simulant plume. The basic equipment and data 

capture environment is shown in Figure 4. Figure 5 

is a photograph of the Gatlin pierside 

preparing for JSLSCAD testing. 

Each test asset or ship utilizes 

a local Global Positioning System 

(GPS) to track its current location 

and transmits this information over 

the low-data-rate (LDR) communications link. The LDR link is an 

omnidirectional link and provides 

for system commands and asset 

tracking information to be transferred to the main processing unit 

or the command console. The asset tracking information is crucial 

to the environment, as it is necessary to reposition or reorient the directional high-data-rate (HDR) link 

antennas. The HDR link is utilized 

to transfer the IR and situational 

awareness (SA) video to the command console. 

A depiction of the command 

console Graphical User Interface 

(GUI) incorporating IR imagery, 

modeling and simulation (M&S) output, SA video, 

and position heading data from each of the platforms in the test is shown in Figure 6. The operator has multiple data windows that can track the 

multiple test assets of the CAPTC environment. 

The user interface is separated into upper and lower viewing areas. The lower display area provides 

a quick look at the status of each asset (i.e., latitude, longitude, and course) and the status of each 

CAPTC processing component executing on that 

platform. The upper display area provides the user 

with the ability to toggle through various options 

Figure 2. Sample Infrared Images Acquired by Titanium Camera

Figure 3. Notional CAPTC Test Environment
28 Naval Sea Systems Command

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Technology

to view the IR video, the situation awareness video, 

the predicted weather information, and the status 

of the simulant plume dispersal.

In addition to the GUI, test event data is sent 

to a simulation display window that tracks and displays each test asset and the simulant plume in a 

3-D display environment using the Simulation Display (SIMDIS) application developed by the Naval Research Laboratory (NRL). As each test asset 

sends its positional data (latitude and longitude) to 

the command console, the console sends the information to the SIMDIS for rendering.

Conclusion

The CAPTC mission presented some complex 

technical challenges. In solving those challenges, 

an IR camera with appropriate capabilities, filters, 

and optics was found that—when coupled with 

the software and architecture developed by engineers at NSWC Dahlgren—enabled the detection 

and tracking of difficult-to-see simulated chemical 

agent plumes. Moreover, a data acquisition system 

was designed and assembled by NSWC engineers 

that handled the significant image processing requirements. A user interface was developed that 

was capable of meeting the rigors of the refereed 

testing environment. A user interface was developed that was capable of meeting the rigors of the 

refereed testing environment. The system was successfully demonstrated during the month of July 

2009. The CAPTC system provides a unique, new 

capability to the testing community that will ensure 

fielded chemical agent detection systems will help 

protect warfighters by alerting them to chemical 

agent plumes that might otherwise go undetected.

Acknowledgments

James Tharp (iO Technologies, Inc.) and Gloria Vaquer (NSWCDD) contributed to this article. 

Reference

1. “Chemical Warfare Agent (CWA) Sensor Testing in an At-Sea Environment—Unique Overwater Test Range Capabilities,” by Dan 

Driscoll and Brian Patrick in Leading Edge, Vol. 6, Issue 3. 

Figure 4. Basic Data-Capture Architecture
29 NAVSEA Warfare Centers Volume 7, Issue No. 2

Infrared Sensor and Image Processing for 

Chemical Agent Plume Tracking Capability

Figure 5. Gatlin Simulant Plume Dispersal Boat Preparing for JSLSCAD 

Testing in Summer 2004

Figure 6. Sample CAPTC Command Console GUI
30 Naval Sea Systems Command

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Digital Array Radar Test Bed

By Ronnie A. Stapleton and Carlos G. Tua

30 Naval Sea Systems Command

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31 NAVSEA Warfare Centers Volume 7, Issue No. 2

Digital Array Radar Test Bed

The Theater Air and Missile Defense (TAMD) 

radar systems envisioned for use in next-generation naval surface combatants are anticipated to 

include high-power apertures operating at S-band. 

While the high power of these systems is driven 

by ballistic missile defense requirements, the radars are, by necessity, multifunction and will also 

be required to detect and track targets at low elevations in clutter. This poses a problem, as the instantaneous dynamic range required of the system to 

support operation in clutter is not easily met with 

traditional receiver-exciter architectures built with 

conventional components. Additionally, the high 

power and narrow beams required for missile defense functions results in a system that is unable to 

search the requisite volume of space in a reasonable time frame. 

To mitigate these issues, radar system architecture has been developed that uses multiple receiver-exciter subsystems operating in parallel in a 

distributed fashion. This results in a system with 

increased dynamic range and stability, as well as 

the ability to search with clusters of beams to increase the system volume search update rate. 

This article provides an overview of the Digital Array Radar (DAR) Project, sponsored by the 

Office of Naval Research (ONR) (Code 313) that 

is performing risk reduction for next-generation 

TAMD S-band radars and on a test-bed system 

that is being constructed to validate system calibration and calibration maintenance. The DAR 

concept is depicted in Figure 1.

The DAR effort concentrates on developing an 

open, modular system architecture that applies to 

the entire radar system, including the development 

and demonstration of subsystem technologies in 

the areas of receiver-exciters, digital beamforming 

and signal processing. A significant attribute of this 

31 NAVSEA Warfare Centers Volume 7, Issue No. 2

Digital Array Radar Test Bed
32 Naval Sea Systems Command

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architecture is the use of an interface control document that specifies the messages used among all 

subsystem elements. A second significant attribute 

of the design is that all system and subsystem control is affected with commands based on time of 

day, resulting in only two interfaces—one for control messages and one for time—entering each subsystem. These two elements allow subsystems to be 

modular in design, which in theory, allow subsystems from multiple vendors to be used to create the 

overall system. To date, the following participants 

have collaborated on various elements of the DAR 

system development: 

•	 ONR

•	 Naval Surface Warfare Center, Dahlgren Division (NSWCDD)

•	 U.S. Naval Research Laboratory (NRL)

•	 General Dynamics Advanced Information 

Systems

•	 Lockheed Martin Government Electronic 

Systems

•	 ITT Corporation

•	 REMEC Defense and Space

The DAR program has progressed to the point 

where end-to-end radar is required to effectively 

test the radar subsystems. To this end, a test bed is 

being constructed that will serve as an instrumentation radar with enough functionality to retire 

risk through engineering tests while demonstrating radar functionality representative of that required in a tactical system. Figure 2 shows the DAR 

Open-Architecture Block Diagram. Construction 

of this test-bed radar is being accomplished by integrating all of the elements behind the antenna, 

which have been the focus of the DAR program, 

along with a surrogate array antenna and associated electronics. The test bed will implement the five 

subsystems marked in blue, while the gray Combat and Navigation System blocks are part of a tactical system and, as such, will not be implemented 

in the prototype. 

Although the focus of the DAR program has 

been on developing the radar subsystems behind 

the antenna, the additional requirement to build 

a prototype radar system necessitated an antenna 

and the associated active-array electronics. In lieu 

Figure 1. DAR Open-Architecture Concept That Enables Multiple Simultaneous Beams and Multifunction Capabilities
33 NAVSEA Warfare Centers Volume 7, Issue No. 2

Digital Array Radar Test Bed

Figure 2. DAR Open-Architecture Block Diagram

of designing a traditional active array with a large 

number of elements, the DAR program is using a 

novel pillbox horn antenna array that offers a combination of high gain, low loss, and simple fabrication.1

 This antenna, designed by NRL, has been 

proven with a four-element prototype and is now 

being constructed with a 64-element design that 

will be used in the risk-reduction test-bed radar 

system. The DAR Test-Bed Antenna Array is depicted in Figure 3.

In order to avoid the development cost associated with a conventional active-array, transmit-receive module, the DAR electronics associated with 

the antenna are built using individual power amplifiers to provide higher power signals on transmit and individual low-noise amplifiers to provide 

low-level signal amplification on receive. They are 

mounted on a cold plate for thermal management. 

A prototype can be seen in Figure 4. 

The digital receiver exciters used in the system are responsible for conversion of digital data 

to S-band signals on transmittal and for conversion of S-band received signals to digital data on 

reception. The data distribution module accepts 

data from the receiver over an industry standard 

10-gigabit Ethernet interface and performs all of 

the complex mathematical digital beamforming 

computations in real time required to produce antenna beams. The system signal and control processing functions are implemented in real time 

with a commercial blade server computer system 

from IBM. Figure 5 shows each of the subsystem 

components that will be used to construct the testbed radar system.

All portions of the test-bed radar system, except for the antenna, were available for testing 

at the General Dynamics Advanced Information Systems facility in late 2008. In order to facilitate early integration, a microwave-fiber optic 

delay line and Doppler repeater were used, along 

with a modest amount of custom-engineered microwave hardware to allow early integration and 

testing of most of the subsystem elements in a 

laboratory environment. Figure 6 shows a photo 

of the microwave-fiber optic delay line and Doppler repeater.

Successful integration, calibration, and testing 

of the elements in this fashion will greatly accelerate the transition of the radar to a functioning test 

bed radiating in free space. The test bed is currently 
34 Naval Sea Systems Command

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Technology

Figure 3. DAR Test-Bed Antenna Array: (a) Antenna has been assembled inside 

a steel frame for rigidity, and (b) Outline of horn and parabolic reflector have been 

constructed out of aluminum standoffs.

(a) (b)

Figure 4. Power Amplifiers, Low-Noise Amplifiers, and Supporting 

Microwave Hardware and Electronics Mounted on a Cold Plate
35 NAVSEA Warfare Centers Volume 7, Issue No. 2

Digital Array Radar Test Bed

Figure 5. DAR Test-Bed Subsystems

DREX Data Distribution Module

Digital Signal Processor and Radar 1- and 10-Gigabit Ethernet Network Switch

Control Processor (IBM Blade Servers)
36 Naval Sea Systems Command

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Figure 6. (a) Microwave Hardware and Microwave-Fiber Delay Line; (b) Doppler Repeater

(a)

(b)
37 NAVSEA Warfare Centers Volume 7, Issue No. 2

Digital Array Radar Test Bed

being assembled at NSWCDD’s Search and Track 

Sensor Test Site overlooking the Potomac River. 

The first phase of the DAR test bed will be based on 

a four-element design with rather modest capabilities. Throughout 2009 and continuing into 2010, 

the system will grow to 32 and then 64 channels 

through the addition of a larger antenna, combined 

with additional receiver-exciter units and processing subsystems. Activities during this time will focus on calibration and calibration maintenance of 

the transmit and receive subsystems, which is critical to achieving high-quality antenna patterns and 

rejection of system clutter. 

To date, all development on the DAR program 

has been accomplished without any contractorspecific intellectual property associated with the 

37 NAVSEA Warfare Centers Volume 7, Issue No. 2

Digital Array Radar Test Bed

Draft – Working Papers

Draft – Working Papers

architecture and subsystem interfaces. The test bed 

that is being built will serve as a tool both to highlight the subsystem capabilities to enable transition 

into a tactical system, but also as a tool for experimentation in areas that can be used to benefit the 

radar community. Lessons learned from all tests 

will be shared with both government and industry 

so that next-generation systems can be successfully 

designed, built, and ultimately, fielded in the hands 

of warfighters in order to increase the capabilities 

of radars to perform their missions in the face of 

current and emergent threats.

Reference

1. W.R. Pickles and M.G. Parent, Pillbox Antenna with a Dipole Feed, 

U.S. Naval Research Laboratory, Washington, DC.
38 Naval Sea Systems Command

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Multifunction Electronic Warfare (MFEW) 

Technology Development Program

By Janine Knott

Figure 1. An artist rendering of the Zumwalt-class destroyer DDG 1000, a new class of multimission U.S. 

Navy surface combatant ship designed to operate as part of a joint maritime fleet, assisting Marine strike 

forces ashore, as well as performing littoral, air, and subsurface warfare. (U.S. Navy photo illustration/Released 080723-N-0000X-001)

38 Naval Sea Systems Command

Sensors

Technology
39 NAVSEA Warfare Centers Volume 7, Issue No. 2

Multifunction Electronic Warfare (MFEW) 

Technology Development Program

The Multifunction Electronic Warfare/Electronic 

Support (MFEW) Program evolved from the Office of 

Naval Research (ONR) Advanced Multifunction Radio Frequency (RF) Concept, Future Naval Capabilities. In support of this initiative, a single Advanced 

Development Model (ADM) contract was awarded to design electronic support functionality per the 

DDG 1000 Electronic Warfare (EW) specification as 

a modular, open, scalable system to support capability growth and application across the entire fleet. 

The Electronic Warfare and EOIR Systems Branch 

at the Naval Surface Warfare Center, Dahlgren Division (NSWCDD) provided key support as the MFEW 

System Engineering lead to the Naval Research Laboratory and the prime contractor, Northrop Grumman Baltimore, in the areas of design, requirements 

assessment, risk assessment, and test and evaluation 

planning. The 2-year ADM project included the detailed design and ADM build and test, followed by 

a transition to Naval Sea Systems Command (NAVSEA) in 2008 via the technology transition agreement 

between ONR and NAVSEA.

Program Goal

The goal of the MFEW Program was to develop a MFEW ADM for the DDG-1000 ship class that 

demonstrated key electronic surveillance capabilities, 

including high probability of intercept, precision direction finding, and specific emitter identification. 

The plan was to conduct MFEW ADM testing that 

satisfied technology development phase requirements to enable a smooth transition to the system 

development and demonstrations acquisition phase. 

The MFEW ADM was leveraged as an opportunity 

to resolve significant cost, schedule, and performance 

risks early in the acquisition process. This was accomplished by using modified Surface Electronic Warfare 

Improvement Program (SEWIP) electronic support 

equipment to ease backfit integration. The ADM design mitigated critical technical risks, refined requirements, and also permitted experimentation and trade 

studies that addressed technical system design and 

development program challenges. Key technical challenges included co-site interference and multipath interference. The program used a modular, scalable, and 

open architecture capable of supporting additional EW functionality and platform configurations including backfit. The flexibility to handle new threats, 

the ability to add capability, and the ability to adapt to 

a ship’s radio frequency interference/electromagnetic interference (RFI/EMI) environment were also included in the design. An image of the DDG 1000 is 

shown in Figure 1 (see title page).

39 NAVSEA Warfare Centers Volume 7, Issue No. 2

Multifunction Electronic Warfare (MFEW) 

Technology Development Program
40 Naval Sea Systems Command

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System Architecture and Design

The MFEW ADM consisted of a single-quadrant 

linear interferometer with a high probability of 

intercept and precision direction-finding capabilities, as well as a series of digital receivers and 

advanced pulse processing that provides antiship 

cruise missile detection and situational awareness in 

the presence of strong interference and dense emitter environments. As mentioned previously, the 

principal design objectives of the MFEW program 

were to reduce technical, cost, and schedule risk 

for the development and production of a nextgeneration ship’s EW system. To accomplish this, 

the team worked with Navy operators to refine EW 

requirements and to develop the EW concept of 

operations, threat characteristics, and scenarios. 

The RFI/EMI environment and ship signature 

requirements of the DDG-1000 class were 

significantly different than in previous ship classes. 

The project was directed to employ Modular 

Open Systems Approach (MOSA) principles to 

provide a total fleet solution and to simplify future 

technology insertions. The design was to also 

provide for growth to a multifunction system, 

potentially including high-gain, high-sensing 

systems; electronic attack capabilities; frequency 

extension; and electro-optic and infrared (EOIR) 

systems and paths to add communications and 

radar functions. The project leveraged systems 

engineering, software, and hardware developed on 

the SLQ-32, the Advanced Integrated Electronic 

Warfare System (AIEWS); the SEWIP; and the 

EA-6B and EA-18G programs. It also used existing 

EW processing from SEWIP and an overwater, 

direction-finding solution proven in the AIEWS.

The MFEW system was further designed to 

use a wide variety of antenna/aperture types as required by the ship configuration and functional 

capability and employs a wideband, distributed radio frequency (RF)-to-intermediate frequency (IF) 

converter with multiple RFI mitigation features. 

Moreover, MFEW uses a common digital receiver/exciter building block that supports acquisition; 

direction finding; modulation on pulse; low probability of intercept waveforms; built-in-test/calibration; and electronic attack. Additionally, MFEW 

employs open, industry standards at all single replaceable unit (SRU) interfaces. Commercial offthe-shelf (COTS) hardware and open software are 

used for all pulse, emitter, and related processing.

The schedule for the MFEW project was very 

aggressive. It began with a kickoff in October 

2005, followed very quickly with a system design 

review in December 2005, a preliminary design 

review in March 2006, and a critical design review 

in June 2006. Factory acceptance testing began in 

December 2006 with integration of the system at 

NRL’s Chesapeake Beach Test Bed in late Summer 

2007 and demonstration in December 2007. The 

compact 2-year schedule allowed for a ship demonstration during the Rim of the Pacific Exercise 

(RIMPAC) in the summer of 2008. The final report, dated August 2009, and analysis data is available from the Naval Research Laboratory Radar 

Division.

In all, the MFEW Program met its goals to 

develop a MFEW ADM for the DDG-1000 ship 

class that demonstrated key electronic surveillance capabilities of high probability of intercept, 

precision direction finding, and specific emitter 

identification. These results will help ensure that 

future Navy ship classes and warfighters will have 

enhanced EW capabilities necessary to identify 

and defeat adversary capabilities.
41 NAVSEA Warfare Centers Volume 7, Issue No. 2

Multifunction Electronic Warfare (MFEW) 

Technology Development Program
42 Naval Sea Systems Command

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Innovation Strategies for Undersea Sensing

By Tom Choinski

Five years ago, the Sensors and Sonar Systems Department of the Naval Undersea 

Warfare Center (NUWC) set off on an organizational experiment. The department’s experiment was the creation of a division consisting of over 60 scientists and engineers 

whose sole purpose was innovation. The organization was named the Emergent and 

Transformational Systems Division, and their mission was to address emerging fleet 

needs by developing and transitioning radically innovative technologies to the fleet. The 

technologies primarily focused on undersea sensing and undersea warfare.

Other divisions in the department and at NUWC also innovate. What made this division unique was that its innovation couldn’t be incremental or along traditional product lines. The innovation had to be radical and game-changing. The focus was to work 

on concepts that could potentially change the calculus of undersea warfare from a sensing perspective. Insofar as the division is still improving and growing its ability to innovate, a lot can be learned from its experiences over the last 5 years.

Innovation is important because advancements of all kinds are taking place at a rapid pace due to globalization. Globalization enables everyone to have equal access to technology on a level playing field. Global leadership will be gained by those organizations 

that can transform their resources rapidly to meet emerging needs and requirements. 

The Navy has emphasized the importance of innovation through several organizations 

such as the Chief of Naval Operation’s Strategic Studies Group (CNO SSG), the Naval 

Warfare Development Command (NWDC), the Office of Naval Research (ONR), and 

the Warfare Centers. The ability to transform resources rapidly has also been identified 

as a key capability for future success by organizations such as the Lawrence Livermore 

National Laboratory and the Central Intelligence Agency (CIA).

Warriors must have a need and the desire to adopt the concepts and technologies 

that are developed. The technologies must also fit within the context of existing doctrine, organization, training, materiel, leadership, personnel, and facilities (DOTMLPF) 

for success. In addition, new concepts must support requirements, operational concepts, 

and acquisition planning. 

The Emergent and Transformational Systems Division achieved success in innovation through a strategy that encompassed education, invention, prototyping, at-sea experimentation, analysis, collaboration, innovation cells, and adoption by the warrior. 

Each of these components of the strategy is subsequently discussed.
43 NAVSEA Warfare Centers Volume 7, Issue No. 2

Innovation Strategies for Undersea Sensing

Education

The division’s education started with the Innovation Strategies Course offered through NUWC 

University. The course focused on the innovation 

equation:

Innovation = f(Invention, Commercialization, Diffusion)

People often confuse innovation with ideation 

or creativity. The course took as its premise that 

innovation is a function of invention, militarization, and the diffusion or the adoption of the idea 

by the warrior. Consequently, a great technological idea that is not adopted by the warrior would 

not qualify as an innovation under this definition. 

The course was a 1-day course developed from extensive research compiled by the author, as well as 

many people at NUWC who provided information 

from related experiences and research on the topic. 

The extensive bibliography for the course—which 

included articles, books, and videos—was donated 

to NUWC’s Technical Library so that everyone at 

NUWC could benefit from this information. Figure 1 shows examples of new additions to NUWC’s 

library resources on innovation.

Invention

Invention leveraged the talented and experienced technical staff of the division. Many new 

products were invented, developed, and prototyped through support provided by NUWC’s bid 

and proposal program; ONR; Naval Sea Systems 

Command (NAVSEA); and Program Executive 

Office, Naval Mine and Anti-Submarine Warfare 

Command (PEO-IWS5A). These organizations 

also supported work in the prototyping, experimentation, and analysis phases of innovation. Figures 2 through 5 show one idea conceived and 

developed under NUWC’s bid and proposal program. The idea was based on undersea distributed networked sensing (UDNS) techniques using 

small or microsized unmanned surface vessels 

(USVs) that could be controlled, navigated, and 

tracked through Web-based tools. The micro USVs 

could be used to provide inexpensive, expendable, 

mobile undersea sensors for riverine applications 

or to investigate potential undersea targets at low 

cost. Figure 6 shows another device that provides 

a Web-based buoyant radio frequency (RF) location function that could be used to locate assets 

that need to be recovered after undersea experimentation.

Prototyping

Prototyping was critical to the development of 

new technology concepts. Existing systems tended 

to offer the best opportunities for prototypes because ideas could be developed quicker by modifying those systems. Moreover, modified systems had 

greater potential for transition into 

an acquisition pipeline and would be 

adopted by the warrior faster if the 

existing system was already proven 

and accepted by the fleet. Figure  7 

shows nontraditional undersea warfare concept prototypes developed 

from standard mobile target devices called Expendable Mobile Antisubmarine Warfare Training Targets 

(EMATTs). These prototypes were 

designed, built, and used during atsea experiments. Modifying existing 

systems enabled rapid prototyping 

and at-sea experimentation in an expeditious manner.

At-Sea Experimentation

At-sea experimentation by the 

fleet is essential to any technical innovation process. Experimentation 

enables the fleet to take new technology concepts and judge the values and merits of the technologies for themselves. Technology 

concepts that offer potential value to the fleet can 

be shaped and modified into a form that will be 

useful to the fleet in the future. In addition, atsea experimentation enables the fleet to develop 

and mature doctrine and operational concepts, 

as well as tactics, techniques, and procedures for 

Figure 1. NUWC Library Resources on Innovation
44 Naval Sea Systems Command

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Figure 3. UDNS Micro USV Compared to Spartan USV

SPARTAN ADM-1 RHIB with

Prototype MicroUSV G1 and E2

G1

E2

Figure 2. UDNS Micro USV
45 NAVSEA Warfare Centers Volume 7, Issue No. 2

Innovation Strategies for Undersea Sensing

Figure 4. Video Image for UDNS Micro USV

Figure 5. COTS Web-Based Control for UDNS Micro USV
46 Naval Sea Systems Command

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Figure 7. Nontraditional Undersea Warfare Prototypes for At-Sea Experimentation

Figure 6. Web-Based Buoyant RF Locator for Experimentation
47 NAVSEA Warfare Centers Volume 7, Issue No. 2

Innovation Strategies for Undersea Sensing

new technology. Through experimentation, technology and fleet concepts are developed in parallel 

to expedite the innovation process. The engineers 

in the division participated in at-sea experimentation, often during adverse weather conditions, 

to collect the data necessary for assessment. Figure  8 shows one of the ships involved in experimentation during TASWEX-04. The experiment 

was conducted immediately following a typhoon.

Analysis

Analysis is critical throughout the invention, 

militarization, and diffusion phases of innovation. 

For acoustics, signal strength is one characteristic that is often analyzed for new concepts. Figure 9 shows the results from a preliminary target 

strength concept for an innovative, acoustic shadow project funded with internal NUWC resources. 

This concept leveraged background noise characteristics to enhance the detection and localization of underwater objects such as submarines. 

The analysis shown in Figure 9 demonstrates how 

the aspect dependencies could be assessed for target strength of a notional submarine. In addition 

to using modeling and simulation tools, the analysis also included operational assessments. Experience gained and relationships developed between 

scientists and engineers and the fleet from at-sea 

experimentation contributes to successful tactical 

and operational performance assessments of new 

concepts and technologies. Working with the fleet 

to determine the operational value of new technologies is important for the adoption and acceptance 

of innovative technologies.

Collaboration

Early fleet experimentation with developmental systems facilitates the adoption of innovaFigure 8. Image of Waves Crashing on Deck of Ship During TASWEX-04 Immediately Following a Typhoon

Figure 9. Target Strength Modeling for Acoustic Shadow
48 Naval Sea Systems Command

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tive technologies through collaboration among the 

technology developers, the end users in the fleet, 

the acquisition community, and the engineers of 

the existing systems. It facilitates communication 

and sets the stage for observation by the end user 

(fleet operators, officers, and commanders) concerning the effectiveness, compatibility to tactics 

and fleet systems, reliability, and applicability to 

their operational requirements. At-sea experimentation of new technologies and concepts allows the 

fleet to make the final judgment and comparison of 

the performance of existing systems. Figure 10 illustrates recent examples of early fleet experimentation of undersea systems. The developmental 

systems were used along with existing fleet systems and as part of a typical integrated antisubmarine warfare (ASW) prosecution involving an 

ASW commander, a destroyer squadron, and ASW 

aircraft. The fleet was proactively involved in the 

tactical employment of the developmental system 

offering hands-on lessons learned.

Collaboration occurs throughout the innovation process, not just in experimentation. Practically all of the division’s success stories involved 

collaboration with other organizations; some within NUWC, some within NAVSEA, others with the 

Department of Defense (DoD) (the services), industry, and international partnerships. The Naval Surface Warfare Center (NSWC) Carderock, 

NSWC Dahlgren, the Air Force, and The Technical Cooperation Program (TTCP) are a few examples of the collaborations that have been integral 

to the division’s success. NUWC has collaborated 

with NSWC in several technology areas. The division leveraged RF radar expertise from NSWC 

Dahlgren, as well as tow-body design capabilities, 

test facilities, and marine architect and design expertise from NSWC Carderock. These collaborative initiatives reduced cost and development time 

while ensuring a higher quality product. Foreign 

collaboration was built through TTCP and through 

partnerships among Australia, Canada, New Zealand, Great Britain, and the United States.

Innovation Cells

Innovation cells are another venue where collaboration is important. They help to facilitate 

analysis. For example, one innovation cell focused 

on issues associated with at-sea experimentation 

and utilized the research on the diffusion of innovation. The results of the innovation cell shown in 

Table 1 illustrate how the 11 attributes of innovation were assessed. 

A discussion on each of the 11 attributes is 

beyond the scope of this article, but note that the 

effort uncovered observability as the crucial attribute to the undersea experimentation process. 

Each of the 11 attributes of the diffusion of innovation was ranked on a scale from 1 to 7, where 

1 indicated a favorable rating, and 7 indicated a 

poor rating. Reliability, radicalness, observability, and economic advantage received poor ratings. Reliability and economic advantage were 

rated poor not because of the performance of the 

system, but because of a lack of communication 

of the performance of the system to the fleet. By 

changing the way we communicated the reliability performance and economic advantage of this 

system, we were able to improve these ratings. 

The rating for radicalness could not be addressed 

because of the fundamental nature of this innovative concept.

However, the rating for observability uncovered a fundamental issue with new undersea sensing concepts. Observability is the degree to which 

the results of an innovation are communicated as 

being visible to others. The observability attribute 

offers unique challenges for the undersea sensing 

environment simply because there is very little 

visibility under the sea. Data is collected during 

undersea experiments and often requires months 

of analysis in the laboratory to assess performance. This is especially important because the 

participants from the experiment are often long 

dispersed by the time the analysis results are reported out in detail. The innovation cell identified 

ways to improve observability during undersea 

sensing experiments. These improvements included:

•	 Planning for Experimentation

◆ Empower riders with a priori knowledge of 

scenarios

◆ Plan to collect mission-based metrics

◆ Disseminate experiment plan to appropriate 

players

◆ Develop a communication plan before the experiment

•	 Communication During Experimentation

◆ Leverage low-bandwidth chat

◆ Improve platform tracking with the ASW Tactical Assessment System (ATAS)

◆ Integrate overhead assets; e.g., Global Hawk

◆ Use acoustic communications (ACOMMS) for 

in situ submarine communications

◆ Use the submarine as the hub for analysis

•	 Analysis After Experimentation

◆ Capture warrior observations via the Web

◆ Conduct collaborative analyses

◆ Disseminate results electronically to solicit 

feedback
49 NAVSEA Warfare Centers Volume 7, Issue No. 2

Innovation Strategies for Undersea Sensing

Figure 10. Collaboration Through Experimentation

49 NAVSEA Warfare Centers Volume 7, Issue No. 2

Innovation Strategies for Undersea Sensing
50 Naval Sea Systems Command

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Adoption

The diffusion of innovation, including adoption by the warrior, remains as one of the greatest challenges in the innovation process to date. 

Figure  11 provides a notional depiction of how 

the innovation and militarization pieces of the innovation equation have been expedited since the 

Cold War. The advent of commercial off-the-shelf 

(COTS) equipment and programs, like the Acoustic Rapid COTS Insertion (ARCI) Program, has 

made great strides in shrinking the invention and 

militarization phases drastically. However, when 

radical—rather than incremental—innovations are 

needed, the diffusion phase may offer the greatest 

opportunity for improvement.

The Emergent and Transformation Systems 

Division has been recognized for its achievements 

and continues to improve upon the strategy that 

success in innovation can be achieved through education, invention, prototyping, at-sea experimentation, analysis, collaboration, innovation cells, and 

adoption by the warrior. The division’s recognition includes the Warfare Center 2008 Innovation 

Award; the PEO-IWS 2007 Award for Innovation; 

the National Society of Professional Engineer’s Top 

10 Federal Engineer of the Year Award; the Rhode 

Island Federal Employee of the Year Award; and recently, recognition in USA Today’s announcement 

for New Faces in Engineering.

By leveraging existing systems and COTS 

equipment, the invention and militarization phases experience rapid turnaround. Striving to ensure 

that new concepts align within the context of existing DOTMLPF improves the diffusion phase 

and maintains the focus on requirements, operational concepts, and integration into acquisition 

planning. Improving the observability of undersea warfare experiments also helps to improve the 

diffusion phase of innovation, which more quickly 

arms warfighters with vastly improved capabilities.

Acknowledgment

The author would like to acknowledge the 

technical contributions to this article from the 

engineers at NUWC who worked on the systems 

discussed, particularly Dr. Michael Obara, Mark 

Vaccaro, Susan Lashomb, Kristy Moore, and Joe 

Gouveia.

Table 1. Innovation Cell Results for Undersea Experimentation
51 NAVSEA Warfare Centers Volume 7, Issue No. 2

Innovation Strategies for Undersea Sensing

Figure 11. The Diffusion of Innovation Challenge

Invention

COLD WAR ERA

10-15 Years

Diffusion

Militarization

NOW

Invention

10-15 Years

Diffusion

Militarization

51 NAVSEA Warfare Centers Volume 7, Issue No. 2

Innovation Strategies for Undersea Sensing
52 Naval Sea Systems Command

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Development

Dual-Band Radar Development: From 

Engineering Design to Production

By Alan L. Tolley and John E. Ball

52 Naval Sea Systems Command

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Development
53 NAVSEA Warfare Centers Volume 7, Issue No. 2

Dual-Band Radar Development: From 

Engineering Design to Production

Overview

The Dual-Band Radar (DBR) Suite is a U.S. 

Navy program. The suite consists of two radars 

integrated with a common controller and single 

interface to the combat system. The DBR radar 

acts according to combat-system-supplied doctrine, which effectively removes the need for an 

operator to run the radar, look at a radar display, 

and make tactical decisions. The radar not only 

provides fast reaction times, but also removes 

much of the potential for operator error in threat 

response.

The radars operate at X-band and S-band, 

and utilize active array technology, a first for the 

U.S. surface Navy. The DBR is scheduled for Initial Operational Capability (IOC) in 2014 aboard 

DDG 1000. The DBR will also be installed aboard 

USS Gerald R. Ford (CVN 78), the lead ship of the 

CVN  21 program. The DBR program started in 

1999 with a contract award for the AN/SPY-3 Multifunction Radar (X-band) to Raytheon. Raytheon 

recently installed engineering development models (EDMs) of both the X-band and the S-band radars at the DDG 1000 Wallops Island Engineering 

Test Center (WIETC). Testing on AN/SPY-3 and 

the S-band Volume Search Radar (VSR) is currently underway. This paper summarizes the effort 

of transitioning from engineering design to production, discusses the upcoming combat-system 

integration challenges, and highlights the advantages of the integrated DBR system to the Navy.

System Architecture 

and Description

The DBR suite is composed of two radars: the 

AN/SPY-3 Multifunction Radar (an X-band radar) 

and the VSR (an S-band radar) and contains a central resource manager for both radars. The DBR is 

connected to the combat system via a single interface. A block diagram of the DBR system is shown 

in Figure 1. The AN/SPY-3 primarily focuses on 

horizon search, low-altitude tracking, and missile support (illumination, uplink, and downlink), 

while the VSR is primarily responsible for volume 

search and tracking.

The design goals of DBR are to:

•	 Operate in harsh littoral environments, 

which often include potentially high-clutter 

areas, as well as land-based jamming

•	 Provide automated ship self-defense capabilities against air and surface targets, including 

low-flying missiles

•	 Provide robust multimission radar

•	 Provide advanced electronic protection (EP) 

capabilities

53 NAVSEA Warfare Centers Volume 7, Issue No. 2

Dual-Band Radar Development: From 

Engineering Design to Production
54 Naval Sea Systems Command

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The AN/SPY-3 consists of three active arrays 

and the Receiver/Exciter (REX) cabinets abovedecks and the Signal and Data Processor (SDP) 

subsystem below-decks. The VSR has a similar architecture, with the beamforming and narrowband 

down-conversion functionality occurring in two 

additional cabinets per array. A central controller 

(the resource manager) resides in the Data Processor (DP). The DBR is the first radar system that 

uses a central controller and two active-array radars operating at different frequencies.1

The DBR gets its power from the Common Array Power System (CAPS), which comprises Power 

Conversion Units (PCUs) and Power Distribution 

Units (PDUs). The DBR is cooled via a closed-loop 

cooling system called the Common Array Cooling 

System (CACS). The power and cooling systems 

are not shown in Figure 1.

The X-band has, in general, favorable low-altitude propagation characteristics, which readily 

support the horizon search functionality of the AN/

SPY-3. A large operating bandwidth is required to 

mitigate large propagation variations due to meteorological conditions (i.e., evaporative ducting). 

The X-band arrays are smaller and lighter than the 

S-band arrays. This allows the X-band radar to be 

positioned higher, which results in improved performance in low-flyer detection and tracking.2

 The 

VSR provides a high-power-aperture product (the 

power-aperture product is a figure of merit of radar systems, the product of the total average radar transmitted power and the antenna area), and 

sufficiently small beam widths to support accurate 

target tracking. The VSR’s primary role is to perform the volume search function.

The AN/SPY-3 and the VSR are both advanced, 

solid-state, active phased-array radars. Solid-state 

arrays offer several advantages:

•	 Lower transmit and receive losses relative to 

passive arrays

•	 Higher operational availability

•	 Graceful transmit degradation versus a single transmitter system2

The REX consists of a digital and an analog portion. The digital portion of the REX provides system-level timing and control. The analog 

portion contains the exciter and the receiver. The 

exciter is a low-amplitude and phase noise system that uses direct frequency synthesis. The radar’s noise characteristics support the high clutter 

cancellation requirements required in the broad 

range of maritime operating environments that 

DBR will likely encounter. The direct frequency synthesis allows a wide range of pulse repetition frequencies, pulse widths, and modulation 

schemes to be created. The receiver has high dynamic range to support high clutter levels caused 

by close returns from range-ambiguous Doppler 

Figure 1. DBR Block Diagram
55 NAVSEA Warfare Centers Volume 7, Issue No. 2

Dual-Band Radar Development: From 

Engineering Design to Production

waveforms. The receiver has both narrowband and 

wideband channels, as well as multichannel capabilities to support monopulse processing and sidelobe blanking. The receiver generates digital data 

and sends the data to the signal processors.

The DBR uses IBM commercial off-the-shelf 

(COTS) supercomputers to provide control and 

signal processing. DBR is the first radar system to 

use COTS systems to perform the signal processing. Using COTS systems reduces development 

costs and increases system reliability and maintainability. Referencing Figure 1, the high-performance 

COTS servers perform signal analysis using radar 

and digital signal-processing techniques, including channel equalization, clutter filtering, Doppler 

processing, impulse editing, and implementation 

of a variety of advanced electronic protect algorithms. The IBM supercomputers are installed in 

cabinets that provide shock and vibration isolation. 

The DP contains the resource manager, the tracker, and the command and control processor, which 

processes commands from the combat system.

The DBR utilizes a multitier, dual-band tracker, which consists of a local X-band tracker, a local 

S-band tracker, and a central tracker. The central 

tracker merges the local tracker data together and 

directs the individual-band trackers’ updates. The 

X-band tracker is optimized for low latency to support its mission of providing defense against fast, 

low-flying missiles, while the VSR tracker is optimized for throughput due to the large-volume 

search area coverage requirements.

The combat system develops doctrine based 

on the current tactical situation and sends the doctrine to the DBR. The combat system also has control of which modes the radar will perform. Unlike 

previous-generation radars, the DBR does not require an operator and has no manned display 

consoles. The system uses information about the 

current environment and doctrine from the combat system to make automated decisions, not only 

reducing reaction times, but also reducing the risks 

associated with human error. The only human interaction is for maintenance and repair activities.

The DBR supports the modes of operation as 

shown in Figure 2. The primary modes for AN/

SPY-3 are horizon search/track while scan, surface 

search/navigation, periscope detection and discrimination, and environmental mapping. During 

engagements, AN/SPY-3 also performs precision 

Figure 2. DBR Operating Modes
56 Naval Sea Systems Command

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Development

tracking, ownship missile tracking, missile communications, and target illumination. The primary mode of operation for VSR is continuous 

volume search, precision tracking, and environmental mapping. Several modes can be performed 

by either band as directed by the resource manager, 

such as limited volume search, precision tracking, 

or cued acquisition. This allows the radar flexibility 

if one of the bands is taxed due to other modes being performed, such as when the AN/SPY-3 is performing illuminations.

Previously, the Navy utilized separate radar systems for air traffic control (ATC), target illumination, target tracking, surface search and navigation, 

missile tracking, and environmental mapping. The 

DBR suite integrates these functions into one system, providing a robust and effective solution for 

the Navy. An integrated system has several advantages over a collection of separate systems—lower 

cost, lower weight, lower ship space required, and 

most importantly, less manning is required.

Engineering Development Model 

(EDM) Integration & Test

The DBR integration and test effort has been 

separated into two parallel efforts. The first effort 

focuses solely on AN/SPY-3, whose development 

started much earlier than VSR. The second effort 

focuses solely on integrating VSR. Both systems 

continue to be integrated and tested separately at 

Wallops Island until late 2009, when both systems 

will be integrated to form the DBR.

AN/SPY-3 Integration and Test

This section discusses the integration and testing at Wallops Island on the Self-Defense Test Ship 

(SDTS), and at the Surface Warfare Engineering 

Facility (SWEF).

Wallops Island Land-Based 

Testing

The AN/SPY-3 Development 

Contract, awarded to Raytheon in 

1999, produced an EDM that was 

installed at Wallops Island, Virginia, in 2003. This installation is 

shown in Figure 3. At this location, the AN/SPY-3 EDM System 

was integrated, and full-power radiation was achieved for the first 

time. Previous subsystem integration activities were limited to 

single-element radiation inside 

a near-field range. As the system 

matured, the effort transitioned 

from a hardware verification activity to a system 

functionality test program, which specifically focused on the Air Search and Track functionality. 

The test program adopted an incremental strategy that began with tracking low-cost targets (e.g., 

Learjets) and culminated with testing against target drones.

Self-Defense Test Ship (SDTS) Testing

After completing the land-based testing in 

2005, the AN/SPY-3 system was shipped to Port 

Hueneme, California, to be installed upon the 

SDTS, the decommissioned USS Paul F. Foster

(DD  964). Figure 4 shows the SDTS and identifies the location of the AN/SPY-3 radar on the ship. 

The test objectives remained similar, but these tests 

were conducted in an operational environment 

with ship-motion and land-clutter backgrounds. 

The AN/SPY-3 completed its testing program in 

2006 but remained on the SDTS until 2008 to observe Ship Self-Defense System (SSDS) testing. The 

testing, completed while installed on the SDTS, 

was essential to production decisions and gave insight into the operational environment.

VSR Integration & Test

The VSR development produced an EDM that 

was installed in the SWEF located at Port Hueneme, 

California, in 2007. This installation is shown in 

Figure 5. This test period focused on hardware 

characterization, including measurements of 

Effective Isotropically Radiated Power (EIRP) 

and system stability. (EIRP is a figure of merit 

for antenna systems and is a way to compare the 

radiated power of antennas.) In 2008, the system 

was shipped to Wallops Island, Virginia, to be 

installed in the WIETC, shown in Figure 6.

Figure 3. AN/SPY-3 Wallops Island Installation
57 NAVSEA Warfare Centers Volume 7, Issue No. 2

Dual-Band Radar Development: From 

Engineering Design to Production

Figure 4. AN/SPY-3 Self-Defense Test Ship Installation

Figure 5. VSR Surface Warfare Engineering Facility Installation

AN/SPY-3
58 Naval Sea Systems Command

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Platform Integration

The DBR is being integrated into both the Zumwalt-class destroyer and the Ford-class aircraft carrier. Each platform introduces its own set of design 

considerations, which range from prime power type 

to sensor priority differences. The examples listed 

in this section are not intended to be complete; they 

represent only a sampling of the platform design 

considerations for both Zumwalt and Ford.

DDG 1000 Zumwalt-Class Destroyer

The physical arrangement of the sensors in the 

Zumwalt deckhouse is illustrated in Figure 7. To 

accommodate integration into the Zumwalt class, 

the DBR design has been uniquely influenced in 

the areas of prime power type, array structure, 

and VSR radome design. With the introduction of 

the Integrated Power System (IPS) for Zumwalt, 

the 440-VAC EDM design was changed to accommodate the ship-power-supplied 4160 VAC. The 

CAPS design is being updated to accommodate 

the voltage change.

CVN 78 Gerald R. Ford-Class Aircraft Carrier

The physical arrangements of the sensors in 

the Ford-class island are illustrated in Figure 8. To 

accommodate integration into Ford class, the DBR 

design has been uniquely influenced in the areas 

of prime power type and sensor priorities. Similar 

to the design changes in Zumwalt, Ford class will 

supply CAPS with 13.8 kVAC. Design updates to 

CAPS are in process to accommodate this change.

In addition to being the primary antiair warfare (AAW) sensor for the Ford class, DBR is also 

the primary ATC sensor. To accommodate this 

added functionality, DBR has added a short-range 

search fence to the baseline functionality set that 

runs concurrently with other functionalities, such 

as long-range volume search and track, horizon 

search and track, etc. To date, the combat system 

and ATC mission areas have had dedicated sensors on aircraft carrier platforms. The concept of 

sharing the DBR across mission areas is a new 

concept and requires careful consideration of how 

the system is integrated.

Future Challenges

In order to successfully deliver the DBR to 

the fleet, a number of activities will be accomplished over the next several years, including the 

completion of the radar integration and test program. Results from testing to date—along with 

Figure 6. Dual-Band Radar Wallops Island Engineering Test Center Installation
59 NAVSEA Warfare Centers Volume 7, Issue No. 2

Dual-Band Radar Development: From 

Engineering Design to Production

Figure 7. DDG 1000 USS Zumwalt DBR Installation Drawing—AN/SPY-3 is shown in red, and VSR is shown in blue.
60 Naval Sea Systems Command

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Figure 8. CVN 78 DBR Installation Drawing—AN/SPY-3 is shown in red, and VSR is shown in blue.
61 NAVSEA Warfare Centers Volume 7, Issue No. 2

Dual-Band Radar Development: From 

Engineering Design to Production

cost reduction, risk mitigation, and production 

activities—have been incorporated into the production designs. The DBR has entered the beginning stages of production, and the challenges of 

producing units in sufficient quantity will continue as this transition from prototype to production occurs. Combat-system integration activity 

for both Zumwalt and Ford class is a significant 

future activity. The combat-system integration 

activity will not be limited to connectivity of the 

system but to also collaboratively work with the 

combat system(s) to ensure that the advanced capability introduced by DBR is fully integrated 

into the combat system.

Conclusions

The DBR is a highly integrated system, providing the Navy with a powerful volume and surfacesearch radar system. The DBR is the first radar to 

use COTS supercomputers to perform signal-processing functions, providing a cost-effective, robust solution. The DBR is also the first dual-band, 

active-array radar suite with a central controller, providing advanced capabilities and flexibility to the Navy. The DBR acts automatically using 

combat-system-supplied doctrine, and DBR does 

not need a dedicated operator. This system reduces system-level reaction times and removes much 

of the potential for operator error in threat response, compared to previously fielded Navy radar systems. This results in reduced operating costs 

and fewer chances for human error. The DBR is designed with graceful degradation wherever possible, providing both reduced operating costs and 

a robust system for the Navy. The MFR and VSR 

radars are currently being tested, and integration 

with the combat systems is planned in the future.

References

1. DDG 1000 Dual-Band Radar (DBR), Raytheon Company, 30 Aug 

2005.

2. Fontana, W. J., and K. H. Krueger, “AN/SPY-3: The Navy’s NextGeneration Force Protection Radar System,” Proceedings of the 2003 

IEEE International Symposium on Phased Array Systems and Technology, pp. 594–603, 14–17 Oct 2003.

61 NAVSEA Warfare Centers Volume 7, Issue No. 2

Dual-Band Radar Development: From 

Engineering Design to Production
62 Naval Sea Systems Command

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Development

International Treaty Verification: 

Cobra Judy Replacement Program

By Penny Moran and Chris Reasonover 

Figure 1. Cobra Judy Aboard USNS Observation Island

Cobra Judy Phased Array Radar

The Cobra Judy radar system provides long-dwell, foreign ballistic-missile data collection in support of international treaty verification. Cobra Judy, aboard U.S. naval ship 

(USNS) Observation Island (shown in Figure 1), has been in service for many years, with 

the ship now over 56 years old. Consequently, both the system and the ship are in need 

of replacement.
63 NAVSEA Warfare Centers Volume 7, Issue No. 2

International Treaty Verification: 

Cobra Judy Replacement Program

The Cobra Judy Replacement (CJR) Program 

includes the design, development, and acquisition 

of a functional replacement ship and mission 

equipment (ME) suite for the current Cobra Judy 

and USNS Observation Island. The CJR’s treaty 

verification mission will remain the same as the 

system it replaces, and it will continue to provide 

worldwide, high-quality, high-resolution, multiwavelength radar data. The systems aboard the 

replacement ship will include high-power, instrumentation-class, X-band and S-band phased-array 

radars and the necessary ancillary equipment to 

support the mission. A close-up of Cobra Judy 

S-band phased array and X-band dish antenna is 

shown in Figure 2. The X-band radar and its antenna dimensions are shown in Figure 3, with the array halves being test-fit for the X-band array shown 

in Figure 4.

Both the X-band and S-band radars will employ 

a variety of waveforms and bandwidths to provide 

operational flexibility and high-quality data collection. The X-band radar will provide very high-resolution data on particular objects of interest, while 

the S-band radar will serve as the primary searchand-acquisition sensor and will be capable of tracking and collecting data on a large number of objects 

in a multitarget complex. The S-band antenna dimensions are shown in Figure 5, with an overall size 

very similar to the X-band antenna.

A common back end (CBE) will handle all 

controls and signal processing for both X- and Sband arrays. The CBE includes:

•	 Displays

•	 Processing Software and Equipment

•	 Communication Suite

•	 Weather Equipment

Figure 2. Close-Up of Cobra Judy S-Band Phased Array and X-Band Dish Antenna
64 Naval Sea Systems Command

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Figure 3. X-Band Antenna

Figure 4. Test-Fit for Upper and Lower Halves of the X-Band Array
65 NAVSEA Warfare Centers Volume 7, Issue No. 2

International Treaty Verification: 

Cobra Judy Replacement Program

Centralizing the software and processing 

equipment maximizes code reuse between the 

two radars and reduces overall cost for the system. 

Many of the CBE components are designed to be 

common, modular, and open between the two radars. The CBE will also be equipped with various 

simulation and test modes to support maintenance 

and training. The CBE is depicted in Figure 6.

Raytheon Integrated Defense Systems (Raytheon IDS) is developing the X-band radar and 

CBE ME, with Northrop Grumman Electronic 

Systems (as a directed subcontractor) developing 

the S-band antenna, pedestal, and antenna servo control system. The CJR ME suite will be installed on a T-AGM 25 platform specially outfitted 

for the mission, as shown in the artist’s concept in 

Figure 7. The ship is being constructed by VT Halter Marine in Pascagoula, Mississippi. When ship 

construction is complete, it will move to Ingleside, 

Texas, for installation of ME, including the heavylift operations of installing the pedestals and arrays. Like the current USNS Observation Island, 

the new ship—recently named USNS Howard O. 

Lorenzen—will be a white-hull, noncombatant. 

CJR’s initial operational capability (IOC) is set for 

31 December 2012.

Engineers at the Naval Surface Warfare Center (NSWC) Dahlgren helped to lead design efforts 

and continue to support development and testing 

by leveraging core technical capabilities in:

•	 Requirements Development and Validation

•	 Systems Engineering

•	 Software Development

•	 Safety and Environmental

•	 Electromagnetic Interference / Electromagnetic Compatibility (EMI/EMC)

•	 Human-Systems Integration (HSI)

Requirements development included managing a diverse technical team made up of both 

government and contracted engineering-support 

personnel, while requirements validation was realized through in-house modeling and simulation 

(M&S). These and other efforts included both direct program office leadership roles and specialized 

engineering support at the working level.

Recognized for its rigorous radar systems engineering, NSWC Dahlgren was appointed as the 

lead or deputy in several of the program of­fice’s 

integrated product teams (IPT) from the program’s 

start. As the X-band IPT lead, NSWC Dahlgren was 

responsible for developing key requirements, monitoring functional requirement allocations, and 

maintaining oversight through design and manufacturing. NSWC Dahlgren also supported the 

S-band IPT as deputy lead and developed many of 

its key requirements. Both IPTs leveraged NSWC 

Dahlgren’s expertise in radio frequency (RF) 

propagation to develop operational performance 

requirements for both radars under a range of 

environmental conditions.

Figure 5. S-Band Antenna
66 Naval Sea Systems Command

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Development

Figure 7. Artist's Concept for USNS Howard O. Lorenzen

As the CBE IPT lead, NSWC Dahlgren 

led and continues to oversee development 

of the software that will integrate the Xand S-band radars. Early in the program, 

NSWC Dahlgren engineers maintained a 

constant presence at Raytheon IDS to participate in the software development process and to collect metrics for the program 

office. This allowed for early detection, reporting, and resolution of software development issues. NSWC Dahlgren also led 

the CJR Operations IPT. This role required 

frequent site visits to all subcontractors to 

witness manufacturing and developmental testing of the ME, which included construction and factory acceptance testing of 

the antenna pedestal, antenna backstructure, X-band array plates, cooling equipment, and power equipment.

NSWC Dahlgren further served as the 

deputy lead in the Integration and Test 

IPTs and continues to serve as deputy lead 

for integration. As the Test IPT deputy, 

NSWC Dahlgren reviewed test plans and 

procedures, witnessed factory acceptance 

and specification sell-off testing, and interfaced with both the Navy and Air Force 

operational test agencies to write the Test 

Figure 6. Common Back End (CBE)

Displays

Data

Processing

Software

Signal

Processing

Software

Communication

Suite

Weather Equipment
67 NAVSEA Warfare Centers Volume 7, Issue No. 2

International Treaty Verification: 

Cobra Judy Replacement Program

Cobra Judy Phased Array Radar

and Evaluation Master Plan (TEMP), further coordinating approval through the Navy, Air Force, 

and Office of the Secretary of Defense (OSD). The 

Test IPT deputy also chaired the M&S accreditation board, which imposed a rigorous verification, 

validation, and accreditation (VV&A) process to 

prime contractor-proposed models to be used for 

final requirements sell-off. As the Integration IPT 

deputy, NSWC Dahlgren served as the government 

liaison between the program office and Raytheon IDS to coordinate witnessing of developmental tests in support of requirement sell-off and to 

maintain sell-off evidence for government acceptance. NSWC Dahlgren engineers also developed 

the sign-off process for the program office.

NSWC Dahlgren additionally served the CJR 

program office in a number of unique and important areas outside of the IPT lead and deputy roles. 

Early in the program, NSWC Dahlgren served as a 

liaison between ME and ship requirements development, subsequently participating in the ship source 

selection process as the program office’s representative and ME expert. NSWC Dahlgren was also a 

major contributor to the milestone B/C documents, 

such as the acquisition plan, acquisition strategy, integrated logistics support plan, systems engineering 

plan, and the TEMP. In addition, NSWC Dahlgren 

engineers drafted the initial security class guide for 

the program office and participated in the final contract negotiation with Raytheon IDS. 

Other engineering support included the CJR 

Principal For Safety (PFS), environmental compliance analysis, EMI/EMC studies, and HSI reviews. As PFS, NSWC Dahlgren served as the CJR 

Program liaison to the Weapon System Explosives 

Safety Review Board (WSESRB). Once the PFS role 

was completed, NSWC Dahlgren continued as the 

lead for safety on the program. NSWC Dahlgren 

also performed analyses to confirm CJR’s compliance with international pollution control standards. One goal of these analyses was to verify the 

ME’s ability to endure the corrosive environment 

produced by a maritime environment and ship 

stack gases. NSWC Dahlgren was also responsible 

for all EMI/EMC topside studies. The EMI/EMC 

study included analysis to minimize co-site interference between the two radars and the between 

the radars and communications suite, as well as 

the ship’s navigation and safety systems. This 

analysis included investigation and mitigation of 

potential issues with off-board RF emitters. Furthermore, NSWC Dahlgren was, and continues to 

be, the lead for dealing with domestic and international frequency spectrum management among 

CJR, the operational Navy, and all other potential 

sources of interference.

One of NSWC Dahlgren’s more critical engineering support roles is to serve as the government clearinghouse for all CJR contract 

deliverables and working documents by hosting 

both unclassified and classified websites. These 

websites enable document and data sharing day 

and night across multiple sites, thereby facilitating the timely turnaround of documents, comments, and analysis products. These websites 

additionally provide a common, controlled document repository for all CJR data supporting government and industry.

In replacing the aging Cobra Judy and 

USNS Observation Island, the Navy, NSWC Dahlgren, and the Air Force are ensuring that CJR will 

succeed in performing the critical mission of international treaty verification over the coming 

decades. 
68 Naval Sea Systems Command

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Program Executive Office Integrated Warfare

Systems Above Water Sensor Directorate 

Common Digital Sensor Architecture

Design Initiatives

By John Schofield

68 Naval Sea Systems Command

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69 NAVSEA Warfare Centers Volume 7, Issue No. 2

Program Executive Office Integrated Warfare Systems

Above Water Sensor Directorate Common Digital

Sensor Architecture Design Initiatives

69 NAVSEA Warfare Centers Volume 7, Issue No. 2

Program Executive Office Integrated Warfare Systems

Above Water Sensor Directorate Common Digital

Sensor Architecture Design Initiatives
70 Naval Sea Systems Command

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The Program Executive Office Integrated Warfare System above Water Sensor Directorate (PEO 

IWS 2.0) initiated the Common Digital Sensor Architecture (CDSA) project to address long-term 

reliability, maintainability, and availability (RMA) 

issues associated with deployed above-water sensors caused by systemic obsolescence. The Naval 

Surface Warfare Center (NSWC) Crane Division 

was tasked by PEO IWS 2.0 to lead the CDSA project to assist with the alignment of sensor support 

solutions and the development of the support infrastructure to achieve and sustain operational 

effectiveness of sensor systems. Through the successful implementation of the CDSA effort, PEO 

IWS 2.0 is providing a means to eliminate sensorunique reengineering efforts; provide stability for 

out-year funding requirements; and consolidate 

contracts, engineering, and support efforts.

The CDSA project is divided into three primary efforts: CDSA Core, Shore-Based Product Data 

Management (PDM), and a CDSA Sensor Integration Kit. The CDSA functional block diagram, 

contained in Figure 1, illustrates the interaction of 

CDSA functional elements.

The CDSA Core comprises common shipboard 

elements consisting of human-machine interface 

(HMI), maintenance and support functions, an integrated data environment (IDE), a sensor tactical host function, and standardized interfaces. The 

CDSA Core provides a common sensor look, touch, 

and feel, while eliminating processes that drive 

knowledge and skill requirements. Additionally, the 

CDSA Core automates the maintenance and supply 

support process; integrates technical and support 

data to eliminate advanced training requirements; 

captures accurate RMA sensor data; and provides a 

common development platform, enabling a reduction to manpower, personnel, and training costs. A 

common architecture and accurate RMA data enable the Navy support community to effectively implement and manage a support strategy to achieve 

and sustain operational effectiveness objectives.

The Shore-Based PDM provides the capability 

to collect, process, and manage all relevant system 

Figure 1. Common Digital Sensor Architecture Functional Block Diagram
71 NAVSEA Warfare Centers Volume 7, Issue No. 2

Program Executive Office Integrated Warfare Systems

Above Water Sensor Directorate Common Digital

Sensor Architecture Design Initiatives

data required to implement an effective sustainment strategy across all designated Above-Water 

Sensors’ life cycles. The PDM also provides the capability to synchronize and extract data from ship 

to shore through utilization of existing Navy Distance Support architecture.

The Sensor Integration Kit includes the hardware and software components required to integrate the CDSA Core into the sensor system. The 

integration of CDSA transitions sensor applications’ execution to general-purpose processors, 

and introduces and expands full system built-intest and built-in-measurement designs to achieve 

sensor supportability requirements.

The CDSA design effort establishes a common modular architecture using Navy Open Architecture guidelines, standardized interfaces, and 

common hardware. The alignment of technical 

architectures across sensor systems enables synchronization of efforts across sensor systems. The 

development of portable sensor applications reduces the risk of technology refresh and technology insertion in the out years. In addition, the 

CDSA design effort reduces system maintenance 

requirements, required shipboard technical skills, 

and workload requirements. Maintenance requirements are reduced by expanding the sensor selfmonitoring capability by embedding all required 

technical information into the system and by providing a design solution that eliminates the requirements for pipeline training, technical training 

equipment, and technical manuals. The ultimate 

goal is to design the CDSA such that an apprentice-level technician can maintain the system. This 

would enable the same technician to maintain multiple sensor systems.

Another objective of the CDSA project is to establish a common set of support measures of effectiveness (operational availability, ownership 

cost) and then manage logistics support to these 

measures in an IDE, which is critical to providing a common life-cycle support strategy. Visibility 

into sensor systems to accurately report and assess 

RMA of the system is critical in meeting fleet requirements and in addressing and sustaining fleet 

needs. Standardization and the accessibility of accurate data is the key enabler. Not only does standardization and accessibility of sensor data allow 

for a network of integrated sensors, it also provides 

visibility to assess the effectiveness of the support 

solution.

In summary, to PEO IWS 2.0, CDSA provides 

a common core capability supporting improved 

operability and maintainability, as well as providing accurate RMA data to monitor sensor support 

solutions. This approach provides continuous visibility into the system to identify where program 

resources should be invested. For the fleet, CDSA 

provides an integrated support solution that sustains operational availability within affordable cost. 

For the technical community, CDSA provides a 

modular software-centric and net-centric system 

to act as a transition platform for technology. For 

the supply support community, CDSA provides 

RMA data to perform supply chain management 

to ensure that support strategy sustains system operational availability at cost.
72 Naval Sea Systems Command

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Development

International Programs

By Michael Madatic

Entering the 21st century, the U.S. has come to deal with the reorganization of Russia and the growth of China, as well as smaller rogue states. As part of an active foreign 

policy, the Navy has pursued international cooperative efforts to meet shared maritime 

interests. The Naval Surface Warfare Center (NSWC) Dahlgren has been committed to 

advancing radar projects both within the Department of Defense (DoD) and alongside 

allied nations over the last several years. And like the U.S. Navy, navies of the U.K. and 

Australia are fielding advanced active phased array radars.

U.K./U.S. Advanced Radar Technology Integrated System 

Test Bed (ARTIST)

The U.S. and U.K. are cooperatively conducting research and development of advanced maritime active phased array radars to support future maritime radars or upgrades to existing systems. Specifically, the U.S. and U.K. are developing and testing two 

advanced phased array radar demonstrators under the ARTIST program. Technologies 

to be applied include adaptive active digital array, signal-processing, digital beamforming, high-range resolution integration techniques, and radar controls. Testing will begin 

in the spring of 2010 at Wallops Island, Virginia.

The U.K. has invested heavily in the development of digital array architecture (i.e., 

analog-to-digital conversion), as well as digital beamforming techniques through critical experiments and algorithm development over the past 20 years. These technologies 

included the construction of an active S-band radar demonstrator and corresponding 

radar controls, including the advanced signal-processing and beamforming techniques. 

These developments were initially conducted by the U.K. under the Multifunctional 

Electronically Scanned Adaptive Radar (MESAR) I and II programs. By establishing a 

cooperative program with the U.K., an existing and proven technology can be expanded 

upon by the U.S. Navy for the development of next-generation radars.

U.S./U.K. ARTIST cooperation provides risk reduction and facilitates the potential 

use by the U.S. of advanced digital phased array developments for air and missile defense radars. The ARTIST program also provides risk reduction to the U.K. development 

of the SAMPSON radar. The technologies being developed under the ARTIST program, 

when combined, will provide a vast improvement to today’s sea-based radar systems. A 

depiction of the SAMPSON Radar is shown in Figure 1.

Benefits from these bilateral cooperative efforts are many and include:
73 NAVSEA Warfare Centers Volume 7, Issue No. 2

International Programs

•	 The incorporation of the U.K.’s technological 

resources (industry/laboratories) and cost 

sharing of technology maturation are common to both nations.

•	 Advanced U.K. digital radar technology permits optimization of U.S.-developed highpowered phased array radar.

•	 The U.K. contribution will provide enhanced 

and specialized digital adaptive beamforming, thereby reducing the U.S. investment required to fulfill U.S. Navy requirements.

•	 The output of this cooperative research and 

development effort represents a quantum increase in adaptive nulling, clutter rejection, 

and sidelobe cancellation capability over 

current U.S. analog-based radars.

•	 The program’s resulting critical technologies 

can be matured in the near term and introduced into new radar designs or as an upgrade backfit to existing radars.

•	 Cooperation accelerates development schedules while providing significant cost avoidance through cross-capture of complementary 

and previously completed nonrecurring engineering.

British Aerospace Systems, Qinetiq, and Roke 

Manor Research are developing the U.K. version of 

the ARTIST test bed. Lockheed Martin is developing the U.S. version of the ARTIST test bed (see 

Figure  2). Roke Manor (U.K.) is also a key partner contributing to the development of a distributed receiver (see Figure 3), while BAE is providing 

the narrow-band, medium-band exciter to the U.S. 

ARTIST.

Australia/U.S. Phased Array 

Radar (AU.S.PAR)

In the late 1990s, the Royal Australian Navy 

(RAN) invested in the development of a solid-state radar system for potential application as 

a midlife upgrade to the Australian Navy’s ANZAC-class ships. This Australian radar development and demonstration effort, termed CEAFAR, 

was of interest to the U.S. since the resulting radar 

was one of the first fully functioning S-band solid-state radars in the world. The specific radar that 

the Australians developed was an engineering development model (EDM) containing two faces of a 

planned six-face system and low-power transmit/

receive (T/R) modules. The Australian EDM system was installed on a RAN ship and completed a 

very successful at-sea test program. Since the completion of the at-sea test demonstration, the RAN 

Figure 1. Sampson Radar

Figure 2. Lockheed Martin ARTIST Test Bed
74 Naval Sea Systems Command

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Development

approved the midlife upgrade to the ANZAC Class 

that included procurement of 10 CEAFAR systems 

from CEA Technologies, Pty, Ltd. A photo of CEAFAR is shown in Figure 4.

In March 2002, under the direction of John 

J. Young, Jr., then Assistant Secretary of the Navy 

for Research, Development, and Acquisition, PEO 

IWS 2.0 (Above-Water Sensors) sent a team of engineers and scientists to Australia to investigate 

the CEAFAR technology and consider the potential application to future U.S. radar developments. 

The U.S. team verified that the technology was innovative and realized that the Australian methods 

for development and manufacturing were very different than those employed by U.S. industries. The 

U.S. Navy quickly concluded that the U.S. could 

gain from cooperation with the Australian CEAFAR solid-state radar technology development.

Maritime solid-state radars are generally manufactured on a single faceplate. The single faceplate 

provides a very rigid structure to hold the radiating 

elements, with structure flatness requirements as 

small as 10 mils across the entire aperture. Each face 

of a solid-state radar typically has an off-array power system, receiving system, and a signal-processing 

system, all controlled with a digital computer.

In the case of CEAFAR, a process to segment 

the aperture was developed, allowing a radar to be 

built from small building blocks (about 12 inches 

by 12 inches) to the full size required. Each building block is called a tile. The tile includes the receive system and the signal-processing system. The 

unique Australian tile concept significantly simplifies the manufacturing process of the antenna.

The U.S. and Australian governments ratified 

the Australia–U.S. Phased Array Radar (AU.S.PAR) 

Project Arrangement (PA) in April 2005 to develop a medium-power and a high-power version of 

the tile concept. The high-power version was subsequently cancelled in 2007 due to poor power 

amplifier performance. The U.S. interests in the cooperative project are focused in five key technology areas for the medium-power project:

1. Segmented Aperture—Understand the process involved in building a large array from 

small building blocks

2. Calibration Methodology—Examine the 

process used to calibrate a segmented aperture.

3. Pulse-Modulated Power Supply—Develop 

an efficient and inexpensive power supply 

to be used in the tile concept

Figure 3. Roke Manor Receiver
75 NAVSEA Warfare Centers Volume 7, Issue No. 2

International Programs

4. Field-Programmable Gate Arrays (FPGA)-

Based High Throughput Signal Processing—Develop a field-programmable gate 

array base signal-processing system embedded in the tile.

5. Vector Modulator Beam Steering—Develop a beam-steering capability based on vector modulators that allow steering during 

transmitted pulses.

The medium-power version of the tile concept 

commenced test in June 2006. 

The Australian company, CEA Technologies, 

Pty, Ltd, is responsible for the development of all aspects of the AU.S.PAR project. Each of the key technology efforts identified above is jointly developed 

via cost sharing and is thus usable by both countries. There is no U.S. industry directly involved in 

the AU.S.PAR project; however, Northrop Grumman has invested heavily in CEA Technologies.

International Program 

Transition

A key concern of international programs is the 

ability to transition individual developments into 

radar programs within each country. If a cooperative program produces a new design, develops a 

new algorithm, or improves the state of knowledge 

in a particular technology, it is important that these 

developments migrate to appropriate radar programs. For research-based projects that are risk-reduction efforts, it may well be concluded that the 

technology is not the right technology to be inserted into a subsequent development effort. This is 

also valid output from such projects.

For the ARTIST program, the transition path 

has already had some success in both the U.S. and 

the U.K. The U.K. continues with the required development for the SAMPSON radar. To a large 

degree, the digital technologies of the ARTIST program are already integrated with the SAMPSON 

radar. Within the U.S., the transition is much more 

subtle. Lockheed Martin is developing the midlife 

upgrade of the SPY-1 system and, as part of this 

design upgrade, the receiver components can be 

traced to the ARTIST program. 

The AU.S.PAR program also has celebrated 

some success. The tile design and manufacturing 

process, as well as the associated calibration techniques, are a product of the CEAFAR program. 

The CEAFAR radar system is destined to be implemented in the midlife upgrade of the ANZAC 

destroyers. The U.S. has not yet transitioned the 

technology gains to date; however, each technology is undergoing evaluation for future new radar 

developments.

Clearly, warfighters representing allied countries benefit tremendously by participating in cooperative research and development programs. 

These navies benefit not only by having more powerful and more capable radar systems, but international compatibility and interoperability among 

these systems improves considerably as well.

Figure 4. CEA-FAR Onboard HMAS Arunta
76 Naval Sea Systems Command

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Development

Rapid Prototyping of Radar Signal Processing

By David Leas

Military sensors employ signal processors to take raw information gathered by the 

sensors to produce data that can be used by warfighters to gain battlespace awareness. 

Signal-processing algorithms are typically mathematically intensive, and thus, are the 

most computationally challenging algorithms seen in military systems. Additionally, the 

quality of battlespace awareness achieved is often directly related to the complexity built 

into the signal processor.

Traditionally, the most demanding sensor signal-processing applications have been 

hosted in hardware-based processing systems. These hardware-based solutions were 

often constructed using application-specific integrated circuits (ASICs) that required 

a very high initial investment cost for nonrecurring engineering. This resulted in designs that were prone to obsolescence due to the limited availability of the components over the long life spans of the military system. Recently, the Navy has begun to 

use digital devices known as field-programmable gate arrays (FPGAs) in radar and 

electronic warfare sensor signal-processing applications previously solvable only with 

ASIC-based solutions. Unlike ASICs, FPGAs allow the creation of digital logic that is 

reprogrammable. Hardware using these devices thereby has flexibility similar to software, which allows the developer to test and upgrade algorithms without the expense 

and risk associated with fabricating a custom chip each time a change needs to be 

made. The downside of this flexibility, however, is that in addition to the design challenges inherent in creating hardware, FPGA development adds many of the difficulties 

found in software development.

Typically, FPGA designs have been developed using a hardware description language (HDL) such as VHDL (Very High-Speed Integrated Circuit (VHSIC) Hardware 

Description Language). This code needs to be validated for functionality and syntax in 

a way very similar to conventional software. However, unlike software, in order to validate the design, a tool called an HDL simulator needs to be employed. An HDL simulator uses a special piece of HDL code called a test bench to stimulate the system under 

test, which allows the simulated system outputs to be validated. After functional validation, the code created with this process is then synthesized to a form suitable for implementation of the design as digital logic in the FPGA.
77 NAVSEA Warfare Centers Volume 7, Issue No. 2

Rapid Prototyping of Radar Signal Processing

As an alternative to conventional VHDL design 

for FPGAs, the vendor Xilinx has created the System Generator for Digital Signal Processing (DSP) 

development tool that allows for creation of FPGA 

designs in the Mathwork’s Simulink environment. 

Simulink is a tool that allows for the graphical creation of algorithms using block diagrams known 

as blocksets and for the subsequent simulation of 

the designs to ensure proper functionality. Another important feature of Simulink is its link with 

Mathwork’s MATLAB environment. MATLAB is 

the most widely used tool to model military and 

commercial signal-processing algorithms and has 

become the de facto standard for DSP design. The 

integration of MATLAB with Simulink allows the 

developer to use code and tools created in MATLAB to stimulate and analyze algorithms developed in Simulink.

The System Generator tool creates functional 

VHDL code from the Simulink environment using 

a special blockset developed by Xilinx. Being integrated into Simulink, it allows the developer to test 

and examine designs through the integration with 

MATLAB. The developer is able to inject test vectors into the system from the MATLAB workspace 

and export system outputs to the MATLAB workspace. This ability facilitates a much faster design 

cycle by moving much of the testing that is normally done with VHDL test benches and simulators to 

validate functionality of VHDL code to testing in 

the Simulink/MATLAB environment. By way of illustration, Figure 1 shows a small System Generator design of a component known as a digital down 

converter that is used in many radar and electronic 

warfare signal-processing systems.

The System Generator design flow takes advantage of the tight integration of Simulink and MATLAB to realize time savings in the development and 

validation of FPGA algorithms. A baseline software simulation in MATLAB of the desired system functionality is created that is used to compare 

with the output of the System Generator model. As 

each subsystem is completed in Simulink using the 

System Generator blockset, it can immediately be 

verified against the MATLAB simulation of the system by replacing the portion of the simulation code 

representing the subsystem with the Simulink subsystem itself. The close integration of the System 

Generator and MATLAB allows for this rapid validation. Upon the completion and validation of all 

the subsystems, the full system can be integrated 

and validated against the original simulation.

After the system is finished and verified in 

Simulink, it is then converted into VHDL using 

Figure 1. System Generator Design of a Digital Down Converter
78 Naval Sea Systems Command

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the System Generator tool. The VHDL created is 

chip-specific to the part specified in the System 

Generator tool. This means that the code generated 

will work only on the specific Xilinx chip; however, it is highly optimized for that chip. The targeted chip can be changed and the code regenerated at 

any time, which helps to avoid obsolescence issues. 

Once the VHDL code is generated, some minor 

work is frequently required to integrate the System Generator portions of the design with the rest 

of the system. The System Generator design flow is 

shown in Figure 2.

The use of the System Generator has resulted 

in significant improvements in the development 

time of several systems and has enabled a much 

faster verification cycle for those systems. One of 

the systems developed using this tool was a signal processor for a low-power, low-cost frequency-modulated continuous-wave (FMCW) radar. A 

system block diagram of the radar signal processor 

is shown in Figure 3.

The initial system required approximately 2 

weeks of development time to complete, with an 

additional 2 weeks of development time for the 

system modifications and refinements. The hardware used for the development was a low-cost 

development board from Xilinx shown in Figure 4; 

the output of the signal processor, displayed on an 

oscilloscope, is shown in Figure 5.

The use of the System Generator allowed for 

subsystems to be tested as they were developed by 

integrating them within a MATLAB simulation 

of the signal processor and comparing the results 

to the simulation alone. If the design were implemented using conventional FPGA design tools, it is 

estimated that the design process would have taken 

6 to 8 weeks to achieve initial capability.

The primary benefit of using the System Generator is the rapid development time. With its 

close integration with MATLAB, much of the verification of the system can be done more quickly than if done in VHDL. The use of specific 

blocks to implement functions also results in efficient code optimized by the chip vendor for use 

on their hardware. The use of the System Generator shortens the development time of FPGAbased signal-processing algorithms significantly. 

On this project, development time was shortened 

by a factor of three, as compared to traditional design techniques, thus allowing systems to be more 

rapidly fielded and upgraded to meet the needs of 

the warfighter.

Figure 2. Design Flow Using System Generator
79 NAVSEA Warfare Centers Volume 7, Issue No. 2

Rapid Prototyping of Radar Signal Processing

Figure 3. Block Diagram of FMCW Radar Signal Processor

Figure 4. Hardware Platform Used for the FMCW Radar Signal Processor

Figure 5. Radar Video Output of FMCW Radar Signal Processor
80 Naval Sea Systems Command

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Development

The AN/SPS-74 Periscope 

Detection Radar System

By Ian Barford, Mark Tadder, and Christopher Gorby

Over the last decade, the Navy’s focus has increasingly shifted from open-ocean operations to littoral warfare. As the performance of the Navy’s traditional antisubmarine 

warfare (ASW) sensors (passive and active sonar systems) degrades in the littoral environment, alternative ASW sensors, such as periscope detection radars, are required to 

provide effective ASW capability in these regions. In response to the U.S. Fleet Forces 

Command (USFFC) Integrated Priority Capabilities List (IPCL), a rapid-deployment 

capability periscope detection radar system program was initiated in August 2006. The 

AN/SPS-74 Radar System (see Figure 1) is currently undergoing test and evaluation at 

the Navy’s Acoustic Test and Evaluation Center on Andros Island, Bahamas. It is also being installed in USS George Washington (CVN 73). This article describes the AN/SPS-74 

periscope detection radar system program and provides an overview of the design features that permit the detection, discrimination, and declaration of periscopes in challenging environmental conditions.

Since the mid-1990s, the Navy has sought to develop a ship-based periscope detection capability. A developmental brassboard system has been periodically deployed 

and extensively tested since 1996 under the Office of Naval Research (ONR) Advanced 

Radar Periscope Detection & Discrimination (ARPDD) program. The ARPDD system 

consists of an AN/APS-137 airborne radar modified to interface with a developmental 

discrimination and post-processing computer system. After rigorous testing, it was determined that the experimental ARPDD system provided acceptable periscope detection and false-alarm rates. After receiving priority on the USFFC IPCL, an advanced 

technology demonstration (ATD) development effort was initiated by the Navy’s Program Executive Office for Integrated Warfare Systems (PEO IWS). The AN/SPS-74(V) 

Rapid Development Capability (RDC) program was initiated in 2006 to develop and 

field an affordable, integrated radar and post-processing system that replicates the performance capability of the ARPDD system by porting ARPDD capability elements to an 

open-architecture (OA)/commercial off-the-shelf (COTS) environment.

The AN/SPS-74(V)1 Radar System, shown in Figure 2, is an X-band, narrowbeam, high scan rate, high processing capacity, periscope detection and discrimination 

radar that rapidly scans the sea surface over a full 360 degrees in azimuth. The radar’s 

primary function is to provide periscope declarations to the shipboard combat system 
81 NAVSEA Warfare Centers Volume 7, Issue No. 2

The AN/SPS-74 Periscope 

Detection Radar System

Figure 1. AN/SPS-74 Radar System

Figure 2. AN/SPS-74(V)1 Radar System

Processor Transmitter / Receiver Pedestal Electronics Assembly

Antenna
82 Naval Sea Systems Command

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Figure 3. Periscope Detection and Discrimination Display

with a multifeature discriminator function and 

then provides automatic target alerts to the operator.

The radar digital display provides an ocean surface picture with rapid-classification aids that help 

the AN/SPS-74 radar operator make an informed 

decision regarding classification of detected targets 

as shown in Figure 3. The radar system is required 

to meet the challenging system specifications for 

the detection and classification of submarine periscopes. This system is required to unambiguously 

display any possible submarine periscope detection data while also displaying very little oceangenerated clutter return. Detecting and reporting 

false alerts is required to be kept to a minimum in 

all types of sea states.

by detecting and discriminating periscopes in 

sea clutter. The system introduces a new highresolution radar consisting of a modern ultra-wide 

bandwidth receiver, a high-reliability transmitter, 

and a 300-rpm scanning antenna. The radar data 

processor features very high throughput data 

processing using COTS processors.

Detection of periscopes is especially challenging since they are often hidden or obscured 

by ocean waves and because they may be exposed 

only for a short time. On every scan, the radar 

passes information to the high-performance data 

processor for immediate isolation of potential 

periscope targets from clutter. Using proven algorithms from the ARPDD program, the data processor processes potential periscope target data 
83 NAVSEA Warfare Centers Volume 7, Issue No. 2

The AN/SPS-74 Periscope 

Detection Radar System

Figure 4. AN/SPS-74 Radar Installation at the AUTEC Test Site

PEO-IWS plans to acquire eleven AN/SPS74(V) systems, with ten systems slated for installation in U.S. Navy aircraft carriers and one system 

designated for installation at the Naval Surface 

Warfare Center (NSWC) land-based test site at 

Oceana Naval Air Station, Dam Neck Annex, Virginia Beach, Virginia. The system is also under 

consideration for future application aboard surface 

combatant ships. In support of the PEO-IWS, radar 

engineers from the NSWC Divisions at Dahlgren, 

Virginia; Port Hueneme, California; and Crane, Indiana have worked closely with the Naval Research 

Laboratory (NRL), Johns Hopkins University/Applied Physics Laboratory (JHU/APL), Northrop 

Grumman Corporation, and Three Phoenix Corporation to achieve program objectives.

The AN/SPS-74 radar system is currently undergoing extensive test and evaluation at the Navy’s Atlantic Undersea Test and Evaluation Center 

(AUTEC) on Andros Island in the Bahamas (see 

Figure 4). This location was chosen for its close 

proximity to deep water, which allows for submarines to enter and exit with ease. The antenna is installed on a platform at a height that is consistent 

with the intended installation location on aircraft 

carriers. Since April 2008, the AN/SPS-74 test team 

has conducted test events in which submarines and 

submarine-like targets have performed scripted 

mission scenarios. Using the data from these test 

events, radar engineers have optimized the system 

discrimination and classification parameters to 

meet the stringent system requirements.
84 Naval Sea Systems Command

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Figure 1. The AN/SPY-1 Phased Array Radar System

Illuminate

Illuminate

Intercept

Intercept

Terminal

Guidance

Terminal

Guidance

Midcourse

Guidance

Midcourse

Guidance

The AN/SPY-1 phased array radar can 

automatically track multiple targets 

simultaneousley while maintaining 

continuous surveillance of the sky from 

the wavetops to the stratosphere.

84

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85 NAVSEA Warfare Centers Volume 7, Issue No. 2

Shipboard Testing of the SPY-1 RADAR

Shipboard Testing of the SPY-1 RADAR

By Randy Strock

Track

Track Track

Detect

Detect

Track

Search

Search

Computer software testing and evaluation engineers might not have the most glamorous positions supporting the U.S. Navy, but their work is 

absolutely vital to warfighter and weapons system 

effectiveness.

Test and evaluation (T&E) is the key process 

that takes the computer programs of the Aegis 

Weapon System from the developmental stage to 

a completed, fielded system. The T&E process begins with unit testing of the developed code by the 

developer. It then moves on to element testing of 

the code against the Computer Program Requirements Specification (CPRS) and, ultimately, to system testing of the computer programs against the 

weapon system specification. While most of this 

testing can be performed in a laboratory setting, it 

eventually must be tested on board the ships where 

it will be used. This is important to the command 

and decision (C&D) and weapons control system 

(WCS) elements, but it is of vital importance to 

the SPY computer program. Only at sea, using real 

shipboard equipment in at-sea environments, can 

the SPY computer program be stressed to its limits. 

A depiction of the AN/SPY 1 Phased Array Radar 

System is shown in Figure 1 (see previous page).

In the 1990s, The Naval Surface Warfare Center (NSWC) Dahlgren was responsible for developing the Aegis Baseline 5.3.8 computer programs. 

Lessons learned from those previous baselines 

Volume 7, Issue No. 2 85

Shipboard Testing of the SPY-1 RADAR
86 Naval Sea Systems Command

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Figure 2. The Guided-Missile Destroyer USS Pinckney (DDG 91)

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proved to software engineers that at-sea testing was 

critically important. Before then, after baseline development and testing was thought to be complete, 

the computer programs would go to sea. Once exposed to that environment, however, many more 

problems were found. Some problems were easily 

fixed, while others pointed to more deeply rooted 

design issues. Subsequently, with the Baseline 5.3.8 

program, the Aegis philosophy of “build a little, 

test a little” was taken seriously and adopted by the 

SPY development team. From the beginning, during early development, the computer program was 

taken to sea as much as possible to wring out problems with the computer program code and transition data to support decisions on the next phase of 

development. NSWC Dahlgren was, and continues 

to be, in a unique position for this kind of work due 

to its close association with both the operational 

Navy and the developmental side of the Navy. The 

result of this at-sea testing approach yielded very 

successful computer programs that are currently 

fielded on 37 Aegis cruisers and destroyers.

In the early 2000s, Aegis Baseline 7 Phase I was 

under development by Lockheed Martin for the 

DDG 91 and follow ships. On these ships, the SPY1D(V) radar was introduced. This third-generation 

SPY-1 signal processor brought several significant changes to the radar, including a large suite of 

clutter-canceling, moving-target indicator (MTI) 

waveforms. Designed and developed in the 1990s, 

this new radar suite had been extensively tested at 

land sites, including developmental testing (DT) 

and operational testing (OT) at the Combat System 

Engineering Development Site (CSEDS) in Moorestown, New Jersey, where Lockheed Martin is located. But it wasn’t until 2003 that a ship was built 

with the radar installed.

NSWC Dahlgren engineers had been involved 

in virtually every phase of development and testing of the SPY-1D(V) radar system for the Navy. 

With the advent of the new radar signal processor 

and new computer programs to support it, it was 

strongly believed that at-sea testing was needed as 

soon as possible to ensure that the radar was giving the Navy the product that it required. NSWC 

Dahlgren engineers led the effort to go aboard 

USS  Pinckney (DDG 91) while it was still in the 

Pascagoula Mississippi, shipyard in the summer 

and fall of 2003. They had prepared for at-sea testing as soon as the ship was put to sea. This effort 

led to the Navy executing an extended Alpha Trial, which contained over 34 hours of testing specifically for the SPY-1D(V) radar to test functions that 

were either impossible to test at land-based sites, or 

where the land-based data was insufficient. NSWC 

Dahlgren engineers were part of the team that developed the test procedures, performed the testing 

on the ship, and analyzed the data afterward. The 

results of this effort were very successful, in that 

many problems were found with the computer program that had been overlooked during land-based 

testing. These problems were then corrected in later 

builds of the computer program. Figure 2 shows the 

guided missile destroyer USS Pinckney (DDG 91).
87 NAVSEA Warfare Centers Volume 7, Issue No. 2

Shipboard Testing of the SPY-1 RADAR

Figure 3. The Guided-Missile Destroyer USS Halsey (DDG 97)

The at-sea testing approach aboard USS Pinckney continued through the remainder of its 

shipbuilder trials and through its transit from Pascagoula to its home port in San Diego, California, 

in 2004. Many hours of specific 

testing were completed by the test 

team, as well as collecting and analyzing data from day-to-day operations. Problems continued to 

be found during this period and 

were fed back to Lockheed Martin to correct in later builds. By the 

summer of 2004, the team began to 

feel that the radar was going to be 

ready for its formal DT/OT testing 

in September.

As the developmental and operational test date approached, it 

became clear that the date was going to slip into 2005. USS  Halsey 

(DDG 97) was targeted for testing 

in September of 2005, but budgets 

were tightening, and DT became 

one of the victims. Consequently, instead of a separate test event 

with its own test aircraft and missiles, DT was ordered to piggyback 

on the existing Combined Combat 

Systems Ship’s Qualification Trials 

(CSSQTs) for the DDG 91 through 

DDG 95. NSWC Dahlgren was instrumental to the team that produced the development test plan 

and influenced the CSSQT testing 

to collect the data that was needed 

to test all the SPY-1D(V) functions 

called for in the Test and Evaluation Master Plan (TEMP). Over 

the next year, as testing progressed 

through the CSSQTs of the five 

ships, as before, more problems 

were found and fixed in the Baseline 7.1 computer program. By the 

time that USS  Halsey completed 

the OT, the SPY-1 radar was ready. 

For the first time in the history of 

Aegis, the SPY radar was deemed 

“operationally effective.” The guided-missile destroyer USS Halsey is 

shown in Figure 3.

During early- to mid-year 

2000s, SPY computer program development shifted to an open architecture (OA) approach. This involved a complete rewrite of the 

computer program. Some design elements were 

brought forward from the preceding baselines, including 5.3.8 and 7.1, but the underlying structure of the program was rebuilt from the ground 
88 Naval Sea Systems Command

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Testing

up. Testing at this time changed completely from 

the 1990s’ approach. On the military UYK computers, the code was developed and compiled on a 

VAX computer and then had to be loaded onto the 

UYK computer in a special laboratory to be tested. 

The process was tedious and time-consuming, and 

laboratory time was limited. With the OA computer program, personal computers (PCs) had come 

along far enough that the SPY computer program 

could be written, compiled, and tested on a single desktop PC. Thus, the same computer program 

that was compiled and run on tactical computers 

on board ship could also be compiled and run on 

a PC. Using a PC, the program interfaced with the 

Testable Computing Environment (TCE) developed by Technology Services Corporation (TSC). 

This capability enabled developers to code and test 

computer programs 24 hours a day at their desks. 

This capability dramatically increased productivity 

and turnaround time, and decreased overall computer program error rates. However, desktop testing could never substitute for testing performed in 

the at-sea environment.

The earliest version of the SPY OA computer program that reached the stage where it could 

be tested on shipboard equipment was a version 

intended to be used with the SPY-1D(V) radar. 

NSWC Dahlgren was instrumental in getting this 

computer program to sea. Support included:

•	 Working with the ships to find test opportunities

•	 Developing the test equipment that went 

aboard the ships to interface with the shipboard computers

•	 Developing test procedures

•	 Participating in the onboard test events

•	 Analyzing the data during and after the 

events

As usual, the at-sea testing proved critical in 

the development of the SPY OA computer program. Many problems were found and corrected in 

the computer program thanks to the at-sea testing 

that was performed. Unfortunately, the SPY-1D(V) 

version of the SPY OA computer program was not 

put into service. However, since it was architected 

to be a superset computer program for all SPY-1 

variants, it was taken as the basis for the Advanced 

Capability Build 2008 (ACB08) Cruiser Guided 

Modernization (CGM) computer program aboard 

Baseline 2 SPY-1A radar-equipped ships.

The ACB08 computer program was first made 

available to USS Bunker Hill (CG 52) in the fall 

of 2008. Once again, the SPY-1 engineering community took the initiative to get aboard the ship 

as soon as possible and collect data with the new 

computer program. Early testing in November 

and December 2008 focused on the simple basics 

of radar operation: search and track of targets 

of opportunity. Beginning in February 2009 and 

continuing through March 2009, more structured 

testing was accomplished. NSWC Dahlgren engineers were involved in the test planning for 

these events and supported the testing aboard the 

CG 52 for a total of 5 weeks during this period. 

Recorded data was received at Dahlgren af­ter 

each test event and was analyzed in the weeks 

afterward. As learned many times before, atsea data proved invaluable in providing an environment that simply cannot be replicated in a 

laboratory setting. Many additional computer 

program problems were discovered and corrected 

in later builds of the program as a result of this 

testing and analysis. USS Bunker Hill (CG 52) is 

shown in Figure 4.

Going into CSSQT of USS Bunker Hill

(CG  52) and USS  Stockdale (DDG 106) in June 

of 2009, at-sea testing of the SPY-1 radar continued. The CG  52 has the latest ACB08 computer 

program build, and the DDG 106 will be running 

with the Baseline 7.1R computer program. While 

weapon system problems are never desired, it is 

always better to discover them beforehand than to 

have ships deploy and go to war with them. Shipboard testing and evaluation of computer programs, therefore, really is vital to warfighter and 

weapons system effectiveness.

Sensors

Testing
89 NAVSEA Warfare Centers Volume 7, Issue No. 2

Shipboard Testing of the SPY-1 RADAR

Figure 4. USS Bunker Hill (CG 52)
90 Naval Sea Systems Command

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Integrated Electronic Warfare Test Facility

By Mark W. Karrick and Ronald D. Wood

The Integrated Electronic Warfare Test Facility opened in 2003 

to enhance the Combat System Integration effort at the Naval Surface Warfare Center (NSWC) Dahlgren. The facility was built 

around the existing AN/SLQ-32(V) Electronic Warfare Reprogrammable Libraries (EWRL) mission, which provides mission updates to fleet electronic warfare databases and oversees the cyclic 

threat-database update process. The facility is used to lead the Navy’s effort to upgrade aging shipboard electronic warfare systems 

and ensure that this critical warfighting data is integrated into the 

combat system while continuing to support the core EWRL mission. 

The Naval Surface Warfare Center, Dahlgren Division (NSWCDD) 

partnered with the Electronic Warfare Systems Project Office (PEO 

IWS-2E) and industry to meet the Navy’s electronic warfare objectives through the Surface Electronic Warfare Improvement Program (SEWIP). SEWIP provides upgrades and new capabilities to 

the current AN/SLQ-32(V) electronic countermeasures system. A 

number of Integrated Electronic Warfare Test Facility projects are 

discussed as follows.

The Integrated Electronic Warfare 

Test Facility

The EWRL is involved in the development of electronic surveillance (ES) and electronic attack (EA) threat databases and active responses. The facility has a robust radar simulation capability in the 

Combat Electromagnetic Environment (CEESIM) and VARIgen 

simulators, which provide both live radio frequency (RF) and digital radar simulation inject (see Figures 1 and 2). Precise radar simulation is vital for accurate ES system identification and EA system 

response. The facility offers a unique site and equipment configuration. The core AN/SLQ-32(V) is divided in half, with the port side 

of the system inside the laboratory and the starboard side on an external tower. This allows for isolated testing on the port side and for 

detection of emitters of opportunity and live overwater and overland 

ES/EA testing from the starboard-side equipment.

90 Naval Sea Systems Command

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91 NAVSEA Warfare Centers Volume 7, Issue No. 2

Integrated Electronic Warfare Test Facility

Figure 1. Integrated Electronic Warfare Test Facility AN/SLQ32(V)5 Electronic Surveillance and Electronic Attack Antenna 

Tower

Figure 2. Radar Simulation and Generation Van

91 NAVSEA Warfare Centers Volume 7, Issue No. 2

Integrated Electronic Warfare Test Facility

Surface Electronic Warfare 

Improvement Program (SEWIP)

SEWIP is a spiral development program for upgrading and providing new capabilities to the current AN/SLQ-32(V) electronic countermeasures 
92 Naval Sea Systems Command

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system (see Figure 3). To date, the program has provided an upgraded open-architecture processor, a 

display console, and the addition of a specific emitter identification (SEI) capability. Future enhancements will involve adding a high-gain/high-sense 

receiver that will significantly improve the sensitivity of the SEWIP system. NSWCDD is the lead 

for threat database software testing for the SEWIP 

Program. The facility has the only shore-based connection between the SEWIP system and SIPRnet; 

NSWCDD used this unique singular link to development the U.S. Navy’s AN/SLQ-32(V) Mission 

Planning website.

Common Display System/Common 

Processor System (CDS/CPS)

The CDS/CPS is the replacement for the 

fleet-standard Q70 display console. NSWCDD is 

researching the migration of the SEWIP Q70 software to the CDS/CPS platform for PEO IWS-2E as 

part of the Aegis Modernization Program. A prototype is shown in Figure 4.

Future considerations for this facility include 

connectivity to the Ship Self-Defense System 

(SSDS) at Wallops Island, Virginia. This would 

facilitate direct SSDS and AN/SLQ-32(V) threat 

database testing. Additional combat system integration with the Sea Air Integrated Laboratory 

(SAIL) at Patuxent Naval Air Station, Maryland, 

will provide integration with the AN/ALQ142(V) and AN/ALQ-210(V) systems aboard the 

Light Airborne Multipurpose System (LAMPS) 

helicopter (see Figure 5). Integrating with SAIL 

will allow threat database analysts to upload ES 

system libraries to LAMPS platforms in real time. 

SSDS and SAIL integration will provide a more 

realistic and combat-system-representative testing environment to help keep the U.S. Navy on 

the forefront of electronic warfare and combat 

system integration.

Figure 3. AN/SLQ-32(V)5 Legacy and SEWIP Configuration
93 NAVSEA Warfare Centers Volume 7, Issue No. 2

Integrated Electronic Warfare Test Facility

Figure 4. Prototype of the CDS/CPS Console

Figure 5. SH-60 LAMPS MK III Seahawk
94 Naval Sea Systems Command

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Dual-Band Radar Program: Government 

and Industry Teamwork Wins the Day

By Brian Hill and David Scalia

Extraordinary events occur in the realm of test and evaluation. Sometimes the 

success of these efforts extends beyond tangible results and provides a 

glimpse of successful Naval Sea Systems Command (NAVSEA) Warfare 

Center government-contractor partnerships. The successful integration 

of the AN/SPY-3 Multifunction Radar (MFR) and the Volume Search 

Radar (VSR) Engineering Development models at the Naval Surface 

Warfare Center, Port Hueneme Division (NSWC PHD), while only one 

part of the overall test program for these radars, exemplifies how government and industry can partner together to achieve success despite seemingly insurmountable challenges.

The MFR and VSR constitute the Dual-Band Radar Program, a system of the DDG 1000 Program that operates in a full-service contract 

environment. It is within this environment that government and industry have nurtured a significant cultural change to combine, manage, and 

execute tasking. This effort led to a partnership among the Navy, prime 

contractors, and various support contractors that further led to increased 

responsiveness and adaptability to meet program executive office (PEO) 

requirements and contractual obligations. The end results have been a 

series of events successfully conducted and completed on schedule and 

within budget.

The government competitively awarded Raytheon Integrated Defense Systems a contract to produce the MFR Engineering Development Model in 1999, which underwent land-based testing at the Surface 

Combat Systems Center, Wallops Island, Virginia, through the end of 

2005. The program of record was to conduct at-sea testing on a yet-tobe-determined platform. Northrop Grumman Ship Systems (NGSS), as lead integrator, selected the 563-ft, 9,200 ton, Self-Defense Test Ship (SDTS), ex-USS Paul F. Foster

(DD 964) to serve as the at-sea platform. What followed was a 9-month, close-working partnership among Raytheon, NGSS, and NSWC PHD (our national team) to design the MFR installation for the SDTS (see Figure 1). Northrop Grumman utilized the 

local industrial base and NSWC PHD personnel via a Work For Private Parties agreement to make efficient use of the allocated budget.
95 NAVSEA Warfare Centers Volume 7, Issue No. 2

Dual-Band Radar Program: Government 

and Industry Teamwork Wins the Day

The SDTS, being a decommissioned Navy destroyer, was designed for operating complex Navy 

combat systems. The MFR, designed for use aboard 

DDG 1000, made various engineering challenges 

immediately apparent in order to adapt the system 

for the SDTS. For example:

•	 The SDTS had no physical location to hold 

the 25,500-lb array enclosure at the proper height, so a tower was designed and constructed pierside (see Figures 2 through 4). 

This necessitated other studies to be performed, including weight and moment analyses.

•	 The SDTS had sufficient power for the MFR 

installation; however, distribution became 

an issue. The load had to be balanced from 

multiple load centers while accounting for 

the ramp rate and other power factors.

•	 The SDTS chilled water system had to be 

modified and augmented to allow sufficient 

cooling of the MFR.

Other challenges included various security requirements, resource sharing with other systems 

installed aboard the SDTS, and corrosion concerns 

related to operating a temporary installation in a 

corrosive saltwater environment.

These challenges were in addition to the normal approvals that surround installing and operating a system, such as frequency approvals, site 

approvals, adherence to National Environmental 

Protection Act requirements, and for this particular effort, coordination with the California Coastal 

Commission. The national team was able to complete the entire installation without mishap within the time and budget allocated. The result was 

the successful completion of the MFR at-sea test 

(DTB2-410) in the scheduled four underway periods via a collaborative Raytheon and government 

test team. At the conclusion of the at-sea testing, 

the MFR was scheduled for installation in a newly 

constructed building, the Wallops Island Engineering Test Center (WIETC), where it would be integrated with the VSR. Construction delays moved 

the building completion date, which required the 

MFR to remain installed on the SDTS. This allowed the MFR test team to continue testing, leveraging off of other programs and their test events.

Figure 1. AN/SPY-3 Multifunction Radar (MFR) Installed on SDTS

Figure 2. MFR Tower Being Installed on SDTS
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An engineering challenge arose when the leverage test events required the SDTS be operated 

without personnel on board. The SDTS has been 

modified to allow full remote control of the entire 

ship, including all permanently installed combat 

systems; so for the primary systems, this requirement was already met. The MFR, however, was 

never intended to be remotely controlled. Once 

again a partnership between Raytheon and NSWC 

PHD engineered a solution, modifying portions 

of the hardware and software to allow 

the MFR to be remotely controlled while 

meeting all safety and security requirements. Challenges again arose with respect to ensuring that interference from 

the MFR would not cause unintended 

consequences for the primary system undergoing test. Raytheon and the MFR test 

team had to work closely with the subject matter experts for each of the various systems to test and validate that there 

were no issues. Ultimately, MFR participated in an additional 2 years of testing 

aboard the SDTS. This feat was possible 

only due to national team collaboration 

across government and industry.

Volume Search Radar (VSR)

The VSR’s path to NSWC PHD 

brought a new set of engineering challenges for the government and industry 

team. Raytheon was awarded a contract 

to develop and build the VSR array with 

Lockheed Martin Maritime Systems and 

Sensors. The plan of record was that after 

completion of the VSR array near-field 

testing at the Lockheed Martin facility 

in Moorestown, New Jersey—which was 

scheduled for completion at the end of 

May 2007—the VSR was to be installed 

in the newly constructed WIETC. Once 

installed, the VSR would undergo initial 

high-power testing and technical performance measurement (TPM) verifications prior to the start of integration 

with MFR. These initial tests were required by NAVSEA Program Executive 

Office Ships (PMS 500) and Program Executive Office Integrated Warfare Systems (PEO IWS 2.0) (responsible for ship 

construction and radars, respectively) to 

make a decision on whether or not to 

proceed with VSR production. However, the delays that prevented the removal 

of the MFR from the SDTS also affected the VSR, and it became apparent to both program offices that this testing was in jeopardy of not 

meeting the schedule. To maintain the programof-record schedule, a study was commissioned in 

August 2006 to determine the feasibility of performing the initial testing at an alternate test site 

until WIETC construction was completed.

The Radar Suite Acquisition Team subsequently determined that the Surface Warfare Engineering Facility (SWEF)—a five-story, 

Figure 3. MFR Antenna Shelter Being Mounted on Tower Onboard SDTS

Figure 4. MFR Signal-Processing Enclosure Being Installed on SDTS
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and Industry Teamwork Wins the Day

50,000-sq ft, oceanfront, land-based test site, located at NSWC PHD—met the criteria for performing the initial testing. Faced with exacting 

time, funding, and resource constraints, the government and industry team convened to boldly 

orchestrate an unparalleled set of actions that accomplished the installation goal within a 4-month 

time frame. The effort enabled the VSR to conduct 

5 months of extensive far-field integration and 

TPM verification that included high-power radio 

frequency (RF), system alignment, antenna patterns, and accuracy measurements.

As with the MFR installation and test effort, 

the government and industry team partnership 

included NAVSEA and Raytheon, with the addition of Lockheed Martin, as well as local southern California industrial support. Concerning 

the major challenges for this project, some efforts 

remained in the government’s purview—namely, 

environmental and site approvals (working with 

the California Coastal Commission), along with 

a concentrated contracting authority effort to 

modify various contract vehicles to enable what 

was an essentially unplanned event.

The engineering challenge involved removing 

an existing AN/SPY-1A radar suite and reconfiguring the building infrastructure to support the VSR 

(see Figures 5 through 8). Since all existing installation drawings were designed for a WIETC installation, considerable effort was required concerning 

design and technical specifications before installation drawings could be produced. Additionally, 

due to the intended temporary nature of the project, a concentrated ef­fort was made to keep cost as 

low as possible by utilizing equipment and plans 

already on hand and by holding infrastructure 

changes to the SWEF to a minimum.

The overall endeavor had several unique challenges that were overcome or mitigated by exemplary engineering practices. One recurring challenge 

was that many of the contributing events had never been attempted before with the VSR. These challenges included:

•	 The VSR’s installation specifications had to 

be adjusted because they were derived from 

the final ship design, where the radar needed 

to be installed into a composite superstructure with the array and load-bearing structure, unlike the SWEF installation.

•	 The VSR system had never been installed 

and connected end-to-end, let alone lifted 

and placed into a full mounting surface or 

attached to the exterior of a building.

•	 Installation required lifting the array with a 

nonexistent lift fixture that would support 14 

tons and allow the array to be tilted back to 

a 20-deg angle.

There was an exact requirement for the flatness 

of the array face after installation across the 16-ft 

array face. The plan was to use adjustable shims 

for each mounting hole. This provided the capacity 

to alleviate some of the flatness margin to counter 

what turned out to be an out-of-tolerance foundation due mostly to lesser criteria when the building 

was constructed and the SPY-1A array installed. A 

series of machined aluminum leveling plates were 

designed that allowed the foundation to maintain 

the flatness required.

VSR had the same requirements for environmental and site approval as the MFR; however, due to the location of the SWEF—within 100 

yards of a public beach—and due to the compressed schedule, a more concerted effort was required. Community leaders were engaged and 

briefed, as were key representatives from all affiliated groups to ensure that all community concerns were addressed up-front. Figure 5. SPY-1A Array Being Uninstalled from the SWEF
98 Naval Sea Systems Command

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Figure 6. The Original Octagonal SPY-IA Opening Was Made Rectangular to Accommodate the VSR

Figure 7. VSR Being Installed at the SWEF
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and Industry Teamwork Wins the Day

The most difficult challenge to overcome was 

one that provided the most important lesson—that 

even a tight schedule should not trump best engineering practices. The initial design of the secondary cooling loop consisted of stainless-steel piping 

of various diameters and specified using flange 

joints in the construction to reduce the complexity and construction timeline. This proved to be an 

error in the design. Excessive flexing of the cooling system due to the high rate of flow and pressure required to cool all of the equipment led to 

continual leaks at all flange mating surfaces despite various efforts to correct this defect. Faced 

with this issue, the team’s engineering decision 

sacrificed 3 weeks of the project schedule by replacing all flanges with butt welds. Schedule impact was ultimately mitigated by resequencing 

other start-up test events (i.e., lighting off and testing the IBM mainframe computers). Consequently, the team was able to alleviate the impact to the 

overall schedule, and as a result of the partnership, 

Figure 8. SWEF with the VSR Installed

Raytheon was able to conduct over 5 months of 

high-power testing and confirm that key performance parameters were being met.

Win-Win-Win Situation

The culmination of an incredible amount of 

coordination across the government and industry 

is a testament to the dedicated professionalism of 

all those involved. The success of the Dual-Band 

Radar Engineering Development Models Project at NSWC PHD demonstrated the team’s ability to put cultural differences aside and focus on 

the common goal of advancing the programs along 

their acquisition paths in support of the DDG 1000 

Program. The result—government and industry 

teamwork wins the day, and Navy warfighters gain 

enhanced radar capabilities.

Acknowledgments

Steve Alkov and Lawana Godwin (CACI, Inc.) 

contributed to this article.
100 Naval Sea Systems Command

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AN/SPY-1B/D Radar Design Changes 

Supporting Aegis Ballistic Missile Defense

By Bernard Ulfers and George LeFurjah

100 Naval Sea Systems Command

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101 NAVSEA Warfare Centers Volume 7, Issue No. 2

AN/SPY-1B/D Radar Design Changes 

Supporting Aegis Ballistic Missile Defense

The Aegis Combat System is an integrated system supporting warfare on several fronts—air, surface, subsurface, and strike—and the Naval Surface 

Warfare Center, Dahlgren Division (NSWCDD) 

has been intimately involved in the development, 

test, certification, and fielding of almost every new 

baseline of the Aegis Weapon System (AWS) since 

the 1970s. This involvement continues as the AWS 

evolves into a critical element of the Ballistic Missile Defense System (BMDS). The Antiair Warfare 

(AAW) components of the AWS are the AN/SPY1B-/D radar system, the Command and Decision 

System, and the Weapons Control System.

Ballistic Missile Defense System 

(BMDS)

The BMDS is a system of systems employing 

a layered defense architecture. It consists of several systems (or elements) at each layer, allowing for 

multiple engagement opportunities against ballistic missiles (BMs) before they reach their intended 

targets. BMs follow three flight phases: boost (preburnout), midcourse (exoatmospheric), and terminal (post-reentry). Currently, interceptors and 

associated sensor systems have been deployed to 

engage BMs in their midcourse and terminal flight 

phases. For instance, the Ground-Based Midcourse Defense element is deployed in Alaska and 

California to defend against Intercontinental Ballistic Missiles (ICBM) and long-range BMs during 

their midcourse phase flight. The AWS sea-based 

midcourse element is deployed to defend against 

short- and medium-range BMs during their midcourse flight phase. Detection, tracking, and discrimination of lethal objects by the associated 

sensors allow the interceptors to utilize hit-to-kill 

technology against the threat while in the exoatmosphere. The terminal phase is the last opportunity to engage the threat. Two elements providing 

this terminal capability are the Theater High-Altitude Area Defense (THAAD) and the U.S. Army 

Patriot Advanced Capability (PAD-3) systems. Figure 1 depicts BM flight phases.

Aegis Ballistic Missile Defense (ABMD) was 

initially fielded as the 3.6.1 AWS baseline to provide 

autonomous (search, track, engage, and kill) BM 

defense against short- and medium-range threats 

and, to provide surveillance support (search, track, 

and hand-off) to other elements for a mix of short-, 

medium-, and some long-range threats. The next 

upgrade to be deployed, the ABMD 4.0.1 baseline, 

enhances capability against short- and mediumrange threats, from unitary to complex separating. In addition to surveillance support to other 

elements, ABMD 4.0.1 is also capable of launching 

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Supporting Aegis Ballistic Missile Defense
102 Naval Sea Systems Command

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Figure 1. Ballistic Missile Flight Phases

interceptors using external, or remote, BM tracks 

(launch on remote).

The next ABMD Weapon System (ABMD 5.0) 

will transition the AAW and ballistic missile defense (BMD) functionality from the older control computers to new commercial off-the-shelf 

(COTS)-based computers allowing for a single 

computing system to perform BMD and AAW 

missions jointly. ABMD 5.0 also brings into play 

the newly developed Multimission Signal Processor, which combines the receiver and signal processing functions supporting AAW and BMD 

waveforms together within one set of cabinets.

The AWS was not originally designed with BMs 

in mind. Designed during the Cold War, it was intended to provide protection from cruise missiles 

and aircraft for groups of combat vessels in bluewater environments. The system’s primary sensor, 

the AN/SPY-1A radar, provided long-range search 

and track coverage. As threats evolved and the international scene changed, the AWS evolved as 

well. In the 1980s, AN/SPY-1B/D radar improvements included higher duty-cycle transmitters, antennas with better sidelobes, increased subclutter 

visibility, and better environmental controls. This 

was primarily to counter electronic attack threats 

and reduce background clutter. In the 1990s, the 

AN/SPY-1D(V) radar provided substantially more 

subclutter visibility, increasing detection and track 

performance against low-flying cruise missiles hidden in sea clutter and near high-clutter littoral environments. Changes were also made to counter 

more sophisticated electronic attack threats. Since 

2000, as part of the BMDS, ABMD capabilities have 

expanded to include defense against BM threats. 

The ABMD Baseline 4.0.1 SPY-1 radar introduces new waveforms, signal processing, tracking, and 

radio-frequency discrimination functionality.

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103 NAVSEA Warfare Centers Volume 7, Issue No. 2

AN/SPY-1B/D Radar Design Changes 

Supporting Aegis Ballistic Missile Defense

Figure 2. AN/SPY-1B/D Radar System Augmented with the BMD Signal Processor

As BM threats become more advanced, the 

AWS adapts. Complex, separating threats typically break up into numerous objects. Some of these 

threats may deploy countermeasures. To properly 

discriminate lethal objects from nonlethal objects 

associated with the BM launch event, kinetic data 

obtained from object tracks—as well as data from 

infrared (IR) images and radio frequency (RF) images—are used. To reduce radar loading, the ABMD 

4.0.1 employs single-beam, multi-object tracking. 

This increases the number of objects that can be 

tracked simultaneously using only one radar beam 

(or dwell). ABMD 4.0.1 also adds a new set of radar 

waveforms, along with advanced digital signal processing. This allows the radar to synthetically combine many pulses in order to construct a synthetic 

wideband RF image with higher range and higher 

Doppler resolution than was possible with the previous baseline.

At the heart of the AWS is the AN/SPY-1B/D 

radar. The radar consists of transmitter, antenna, receiver, signal processor/waveform generator (WFG), and computer control components. In 

ABMD 4.0.1, these components are augmented with an adjunct signal processor known as the 

BMD Signal Processor (BSP) (see Figure 2). The 

BSP comprises a new WFG, receiver, digital signal 

processor (DSP), and control computer. These new 

components are integrated into the existing components to provide bursts of the new radar pulses, along with special processing suited for tracking 

and discriminating BM objects.

Design and development challenges include 

the careful scheduling and timing of successive radar beams using the new waveform bursts, along 

with the legacy waveform pulses. Land clutter and 

electromagnetic interference (EMI) found in the 

operational environment continue to pose design 

challenges as well. Another challenge facing ABMD 

4.0.1 is determining the period of time that radar 

system calibration will hold.

Aegis BMD Program 

Office Support

During the design and development of the adjunct BSP, the ABMD Program Office established 

a Joint Navy/Lockheed-Martin Radar Integrated 

Product Team (IPT) comprising organizations including:

•	 Naval Research Laboratory

•	 NSWC Port Hueneme Division

•	 John Hopkins University Applied Physics 

Laboratory

•	 Technology Services Corporation

•	 Massachusetts Institute of Technology (MIT) 

Lincoln Laboratory

•	 System Engineering Group

The IPT was intended to cooperatively and 

jointly explore design solutions, such as the mitigation of EMI effects, mitigation of land-clutter 

effects, optimization of sidelobe blanking algorithms, and assessment of different RF features as 

discriminants. NSWCDD provided Navy oversight 

and expertise in co-leading the IPT. NSWCDD 
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also provided support to the ABMD Program Office, managing reviews of specifications as part of 

the design review process. Today, NSWCDD continues to exercise a leadership role in the joint 

Radar IPT for ABMD 4.0.1 and the follow-on baseline, ABMD 5.0.

NSWC Radar Clutter Modeling

Engineers at NSWCDD are involved in the 

ABMD 4.0.1 Program radar development process 

from generation of radar requirements to design 

to verification to certification. Clutter modeling results produced by the in-house, site-specific radar clutter model—the Littoral Clutter Model 

(LCM)—were instrumental in driving system requirements for clutter mapping, detection, and 

mitigation algorithms, as well as sidelobe blanking algorithms. NSWCDD engineers also provided 

significant technical support in the detailed design 

and verification of these algorithms.

The LCM is a site-specific simulation of the 

backscatter from both land and sea for a shipbased radar in a littoral environment, in the presence of ducting. The inputs to the model include:

•	 Geographic location of the sensor

•	 Maximum range and angular width of the 

azimuth sector over which the radar is to 

transmit

•	 Radar parameters, such as frequency, antenna height, beamwidth, and elevation angles

In order to evaluate the effect of atmosphere 

and the sea surface on both propagation and clutter, estimates of the atmospheric refractivity over 

the region and the sea state are also used as inputs. 

The principal output from the model is simulated 

clutter power along each azimuth in the propagation sector, which may be plotted as the Plan Position Indicator (PPI) display of a clutter map.

To simulate the diffraction and shadowing of 

a clutter patch over variable-height, site-specific 

terrain, a parabolic wave equation model is executed with terrain contours from Digital Terrain 

Elevation Data (DTED) files provided by National 

Geospatial-Intelligence Agency (NGA). The United States Geological Survey (USGS) provides a 

global land-cover database, Advanced Very High 

Resolution Radiometer (AVHRR), with 24 terrain 

type classifications, along with a latitude and longitude worldwide reference. The terrain types are 

correlated with the DTED data to associate appropriate electrical properties and surface roughness 

values with each patch of terrain. With the terrain 

heights, electrical properties, surface roughness, 

and atmospheric refractivity as inputs, the PWE 

Model is able to compute a propagation factor for 

each clutter patch along each propagation path. In 

order to model backscatter from patches of terrain 

or ocean surface, the Navy-Standard Georgia Institute of Technology (GIT) sea-clutter model is 

employed. For land clutter, the Low-Angle Radar 

Empirical Land Clutter Model designed by J. Barrie Billingsley at MIT Lincoln Laboratory is employed.

NSWC Radar Calibration 

Test Support

Verification of radar system calibration at the 

land-based test site in Moorestown, New Jersey, 

presented system engineers and the ABMD program office with unique challenges. Calibration 

of the new BSP waveform bursts through the radar equipment must be performed periodically by 

capturing radar returns from a balloon-borne machined calibration sphere away from sea or land 

clutter. These returns are then tuned to optimize 

image-processing performance. To completely 

capture the responses of the whole radar system is 

a time-consuming process. It is, therefore, in the 

best interests of the operational Navy for the designers to reduce the number of these sphere track 

events to once per 6-month period. Verifying that 

such a calibration event produces good performance consistently over a long period of time requires a repeatable test with good controls on the 

test environment. A solution was proposed by 

NSWCDD engineers to provide and man a tethered aerostat system equipped with a radar sphere 

target attached to the tether near the land-based 

test facility, the Combat System Engineering Development Center (CSEDS) in Moorestown, New Jersey. NSWCDD engineers from the Potomac River 

Test Range Branch have supported similar tests for 

many years and are currently supporting this effort 

over a 9-month test period. Figure 3 shows photographs of an Aerostat Test.

As the AN/SPY-1B/D radar evolves to meet 

ABMD requirements, engineers at the Naval Surface Warfare Center (NSWC) Dahlgren will continue to support the evolution of the ABMD 

Program. As a result, our Navy and our nation will 

continually remain well postured to defend against 

BM threats.
105 NAVSEA Warfare Centers Volume 7, Issue No. 2

AN/SPY-1B/D Radar Design Changes 

Supporting Aegis Ballistic Missile Defense

Figure 3. Aerostat Test, Rancocas State 

Park, New Jersey, 2 December 2008
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The AN/SPS-48G Radar System 

Sustainability Upgrade

By Daniel Quigley, Lance Walters, Caitlin McInnes, and Christopher Gorby

The AN/SPS-48 radar system provides three-dimensional air surveillance for U.S. 

Navy aircraft carriers, amphibious assault ships, and amphibious dock landing ships. Its 

mission is to provide air defense surveillance, support air traffic control, supply accurate 

target coordinate data for weapon queuing, and support combat air patrol aircraft operations during peacetime and in war. The current version of the AN/SPS-48 radar, the 

AN/SPS-48E, has been in service in the U.S. Navy since 1987 and is expected to remain 

in service beyond 2030. In order to ensure that the readiness and rapid-response capabilities of the U.S. Navy remain intact, the SPS-48G Radar Obsolescence Availability Recovery (ROAR) program was initiated. The ROAR program is responding to a need for 

improvement of declining reliability, maintainability, and supportability issues. This article describes how these issues are addressed via an open architecture (OA)-based system redesign that leverages new technology and by the addition of a new embedded 

training and system-support methodology.

Introduction

For over a decade, the AN/SPS-48E radar has experienced a decline in reliability, 

maintainability, and supportability, which has resulted in diminished operational availability and an increase in life-cycle support costs. Despite attempts to alter this continuous decline with various modifications, the AN/SPS-48E radar continues to operate 

below acceptable levels. The ROAR program was initiated to reverse this trend and respond to the need for a system redesign that introduces

•	 A sustainable OA processor

•	 More reliable and current technologies

•	 Improved diagnostics

•	 A performance-based product support strategy

Open Architecture Design Approach

The primary objective of the U.S. Navy OA initiative is to design and build affordable naval warfare systems that support current performance requirements, reduce future potential performance upgrade costs, and achieve portability, modularity, 

and interoperability throughout their life cycle. To comply with this initiative, the 
107 NAVSEA Warfare Centers Volume 7, Issue No. 2

The AN/SPS-48G Radar System 

Sustainability Upgrade

AN/SPS-48G(V)1 has been designed to meet the 

U.S. Navy-defined Open Architecture Computing 

Environment (OACE) Category 3. This designation requires a fully OACE-compliant application 

implementation and infrastructure, including 

use of a Portable Operating System Interface for 

Unix (POSIX)-compliant operating system and 

Object Management Group (OMG) Data Distribution Service (DDS) publish/subscribe middleware. With the implementation of this standard, a 

baseline for interoperability among systems with 

minimal integration effort has been established as 

illustrated in Figure 1.

Redesign With Current 

Technology

To address the current and emergent obsolescence issues within the AN/SPS-48E Radar system, 

and in recognition of system reliability, maintainability, and cost drivers, the AN/SPS-48G program effort follows a practical design approach 

with several major modifications. The first major 

item is the introduction of a new solid-state, singlestage amplifier to replace the unreliable and costly 

AN/SPS-48E microwave tube-based First- and 

Second-Stage Amplifier. This new unit consists of 

180 solid-state, radio-frequency amplifiers (RFA) 

installed in an architecture that provides redundancy and allows for graceful degradation. This 

solid-state design was prototyped and tested in the 

late 1990s and provides a highly reliable and stable output for further amplification in subsequent 

stages of the transmitter. This new solid-state, single-stage amplifier will substantially increase system availability while significantly reducing 

transmitter maintenance time.

The second major modification is the new Receiver/Processor unit, which completely replaces 

three units from the SPS-48E System (the Receiver, Processor, and Auxiliary Detection Processor 

units). This replacement results in an 87% reduction in unique lowest replaceable units (LRUs), reduces the number of RF cables from over 200 to 

just 33, and eliminates thousands of backplane 

Figure 1. AN/SPS-48E Radar Obsolescence, Cost, and Maintainability Problem Areas
108 Naval Sea Systems Command

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wires, resulting in a marked improvement in system reliability and availability.

Through the use of redundant commercial offthe-shelf (COTS) single-board computers hosted in an VMEBus VITA 41.3 architecture, the 

OA processor design will ensure the sustainment 

of the COTS-processor computing environment 

through a cost-effective tech-refresh program (see 

Figure 2). Maintainability and supportability improvements result from an improved maintenance 

system centered on a more comprehensive and intuitive Built-In Test (BIT) function that is fully integrated with embedded technical data, job aids, 

and training.

Performance-Based Product 

Support Strategy

Although the AN/SPS-48G(V)1 system is 

designed to fulfill the AN/SPS-48E top-level 

performance requirements, the philosophy of supportability is substantially different. For this system 

to be in service beyond 2030, the program applies 

new, innovative concepts into the design by developing a product support strategy that synchronizes 

traditional support elements into a performancebased environment. Responding to policy guidance OPNAVINST 1500.76, the AN/SPS-48G(V)1 

radar design reduces the number of organizational-level maintenance tasks and the time required to 

Figure 2. AN/SPS-48G(V)1 Radar System Hardware Modifications
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The AN/SPS-48G Radar System 

Sustainability Upgrade

perform these tasks by 62%. The AN/SPS-48G(V)1 

employs a new Maintenance System that improves 

maintenance accuracy, reduces the time and cost 

to repair, and reduces the knowledge and skill level 

requirements to effectively perform maintenance.

The Maintenance System consists of an expanded BIT function that includes:

•	 An embedded Diagnostician package

•	 An embedded Technical Integrated Digital 

Environment (TIDE)

•	 A Radar Display and Control Function 

(RDCF)

The improved fault-isolation accuracy of BIT, 

coupled with reduced system complexity, makes 

it possible to employ a performance-based maintenance strategy. The key paradigm shift to note 

is that the maintenance methodology focuses the 

shipboard technician on what, when, and how to 

perform system maintenance, not on understanding volumes of technical information in order to 

maintain the system. The integrated maintenance 

system triad of BIT, TIDE, and RDCF creates, prioritizes, and schedules maintenance sessions to 

perform all corrective and preventive maintenance 

actions. All of the procedural and technical information necessary for the technician to perform 

the maintenance action is intuitively presented 

at the RDCF when the technician activates a session. Using the established Distance Support network, expert technicians ashore will assist with 

fault isolation when BIT cannot isolate the fault to 

one LRU or when the task is beyond the immediate knowledge and skill level of the onboard technician. The maintenance system components are 

depicted in Figure 3.

This new maintenance strategy also results in a 

significant reduction in the training requirements 

for the system. A Job Task Analysis was performed 

and identified the system-specific knowledge and 

skill gaps that are not satisfied by the existing apprentice training pipeline and embedded Maintenance System. To compensate for these knowledge 

and skill gaps, training for the SPS-48G technician 

includes 3 weeks of hands-on familiarization training to be taught at the Center for Surface Combat 

Systems facility at Dam Neck, Virginia.

Conclusion

Responding to the need for improvements in 

reliability, maintainability, and supportability, the 

ROAR program is a unique radar system that offers 

an OA-based system upgrade that decouples hardware and software to allow for affordable future 

technology growth. The simplified design has successfully implemented a methodology that reduces 

the number of maintenance-significant items and 

organizational-level maintenance tasks, as well as 

the knowledge, skills, and time required for shipboard maintenance. These changes will drive the 

system to achieve and sustain an increased operational availability, while at the same time lowering 

its life-cycle costs.

Figure 3. AN/SPS-48G(V)1 Maintenance System Components

NIAPS: Navy Information Application Product Suite 

IDE: Integrated Digital Environment (IDE)
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Technical Authority and the Future of Radar

By Roger Kniceley

110 Naval Sea Systems Command

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111 NAVSEA Warfare Centers Volume 7, Issue No. 2

Technical Authority and the Future of Radar

Radar systems have been critical to the Surface 

Navy since the initial introduction of the CXAM 

radar installed on the battleship California; the aircraft carrier Yorktown; and the heavy cruisers Pensacola, Northampton, Chester, and Chicago in 1940. 

Since that initial introduction, radars have been 

expected to improve their functionality and performance. Performance has increased from basic 

detection of ships and aircraft for self-protection 

and gun fire control to the present requirements to 

detect and track maneuvering, sea-skimming missiles, as well as the discrimination of lethal objects 

from ballistic missiles. Radars have also evolved 

from stand-alone systems with raw video displays 

to being fully integrated in the fire-control loop and 

the force-level network of sensors able to provide 

situational awareness over hundreds of miles. With 

this increased complexity comes the need for more 

rigorous systems engineering and coordination to 

ensure that the “system of systems” is properly integrated, interoperable, and meets the functional and 

performance requirements. 

Defense Acquisition System 

Department of Defense (DoD)

DoD Instruction 5000.2 provides the policies 

and principles that guide all acquisition programs 

and defines a Systems Engineering Technical Review (SETR) structure to balance performance and 

cost while managing risk. Along with this basic 

systems engineering structure, the Systems Commands (SYSCOM) have been entrusted with execution of the “Technical Authority,” which is the 

authority, responsibility, and accountability to establish, monitor, and approve technical standards, 

tools, and processes. The goal is to employ consistent, disciplined collaborative engineering processes that provide safe, reliable, effective, integrated, 

timely, and affordable systems.

Technical Authority Warrant

Virtual SYSCOM Engineering and Technical Authority Policy, VS-JI-22A, defines the engineering and technical authority policy and actions 

needed to support program managers (PMs) and 

the fleet in providing best-value engineering and 

technical products. The instruction defines the 

Technical Authority roles and responsibilities of 

the SYSCOM Commanders, the Deputy Warranting Officers, and the Technical Warrant Holders 

(TWHs). VS-JI-22A lists the following responsibilities of TWHs, organized by the seven competencies critical to being entrusted and empowered 

as a TWH. 

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Technical Authority and the Future of Radar
112 Naval Sea Systems Command

Sensors

Modernization

1. Setting Technical Standards—Establish technical policy, standards, tools, requirements, 

and processes, including certification requirements.

2. Technical Area Expertise—Provide technical advice to the fleet, depot chief engineers, 

and other DoD customers. Maintain technical 

expertise and interface with the Science and 

Technology (S&T) community.

3. Ensuring Safe and Reliable Operations—Ensure that safety and reliability are properly addressed in technical documentation. Ensure 

that products are in conformance with technical policy, standards and requirements. Where 

they are not, identify options and ensure that 

risks are technically acceptable.

4. Systems Engineering Expertise—Ensure engineering and technical products meet Navy 

needs and requirements, including interoperability. Identify and evaluate technical alternatives, determine which are technically 

acceptable, and perform risk and value assessments. 

5. Judgment in Making Technical Decisions—

Provide leadership and accountability for 

all engineering and technical decision-making. Promote and facilitate communications 

to ensure that appropriate personnel and organizations are aware of, and are involved in, 

technical issues and technical decisions.

6. Stewardship of Engineering Capabilities—Ensure that an appropriate engineering and technical authority support network is established 

for the warranted technical area and provide 

leadership for the support network.

7. Accountability and Technical Integrity— Exercise integrity and discipline to ensure the 

soundness of technical decisions. Keep organizational Chain of Command informed of issues and decisions.

NAVSEA has a long history with Hull, Machinery, and Electrical (HM&E)-related TWHs. 

However, VS-JI-22A defines six types of TWHs, 

including: Platform Design Managers, Chief Systems Engineers, Cost Engineering Managers, 

Technical Process Owners, Depot Chief Engineers, 

and Technical Area Experts (TAE). Within the 

general category of TAE, there are several different 

competencies, including marine engineering, human systems, test and evaluation, and warfare systems. SEA05 has designated a number TWHs to 

support the various warfare system elements, including: guns, missiles, electronic warfare, electrooptics, and radar. 

The scope of the Radar TWH includes the 

RDT&E, acquisition, and in-service support for 

all Surface Navy radars. To fulfill these roles and 

responsibilities, the TWH must work with the 

various radar system PMs in all phases of radar 

development. This is accomplished by maintaining open lines of communications, participating in 

the various SETRs, and generally maintaining an 

awareness of the various radar-system design and 

support issues. It is important to understand that 

TWHs in no way change the responsibilities of the 

Program Executive Offices (PEOs), Major PMs, 

or individual PMs. The TWH is intended to be a 

partner and independent source of expertise and 

review to help provide the best and most cost-effective products to the warfighter.

Radar TWH Activities

It is a very active time for the Surface Navy radar community, with systems in all stages of acquisition. The Radar TWH is not only involved in 

the development of radar systems, but also in the 

integration of those systems into combat systems 

and ships. Primary TWH involvement occurs at 

the SETRs; however, when properly integrated, 

there are numerous other opportunities for the radar TWH and PMs to collaborate. The following 

list will provide some insight into the scope and 

breadth of the Radar TWH role and support that 

has been provided: 

General Radar Analysis and Concept Definition

•	 Review of the radar requirements and concepts for CG(X) and Future Surface Combatant

•	 Review of the Integrated Air and Missile Defense Layered Defense Study

•	 Assessment and monitoring of solid-state, 

high-power amplifiers and vacuum tube radio frequency (RF) source development

•	 Support for continued management of the 

Surface Navy Radar Roadmap

New Radar System Development

•	 Review and comment on the Air and Missile 

Defense Radar (AMDR) Capability Description Document

•	 Participate in contractual source selection 

•	 Serve as panel member on numerous reviews 

for Dual-Band Radar (DBR) and SPY-1 Multimission Signal Processor

•	 Review and evaluate risk-mitigation activities associated with the DBR High-Power 

Module and radome development
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Technical Authority and the Future of Radar

Combat System and Ship Integration

•	 Review of DDG 1000 Combat System simulation strategy

•	 Assess and recommend for DBR integration with Battle Force Tactical Trainer for 

CVN 78

•	 Review of the improved sensor integration 

architecture and algorithms for the Amphibious Improvement Program

•	 Review and recommend for TRS-3D radar 

performance analysis for the littoral combat 

ship (LCS)

Deployed System Support

•	 Investigation and analysis of root cause for 

Aegis SPY-1 radar adaptation data issues

•	 Investigation and study of operational radar 

and commercial system interference

Future Radar System Focus Areas

We are approaching the point where technology is available to design a radar system that can 

satisfy almost any foreseeable performance requirement: detection of missiles as they come over 

the horizon; detection, resolution, and identification of threats at hundreds of miles; and accurately 

tracking and correlating maneuvering threats from 

multiple sensors to create a complete situational 

awareness over the entire theater. However, that 

does not mean that S&T and systems engineering 

are not required. There are still many critical problems that must be addressed that require broad 

community attention and coordination. 

One of the primary concerns for future systems is procurement cost. Future radar systems 

are projected to cost hundreds of millions of dollars to develop and an equivalent amount to procure one deployable system. While these costs 

may be justified for major combatants, the Navy 

needs lower cost radar systems that can be affordably developed, integrated, and installed on 

smaller ships. Focus must be maintained on this 

objective as we develop the future AMDR so that 

both hardware and software components can be 

used to quickly and economically develop and 

build less-capable variants.

Another important aspect of reducing future 

costs is driven by system efficiency. Historically radar systems have had to deal with significant 

transmit, receive, and processing losses. To compensate for these losses, radar designers increased 

transmit power or antenna size. Modern phasedarray radar systems have gotten rid of most of these 

losses but now suffer from low-efficiency, highpower modules. The low module efficiency does 

not directly impact system performance; however, it does drive the size of the radar power supplies and cooling systems and, therefore, impacts 

radar system weight, which—for very high-performance radars—can become a significant driver for 

the overall ship’s power generation system.

Legacy and RF Systems

The above focus areas were concerned with 

new radar systems, but legacy systems also require 

S&T investment. Many of the radar systems currently in the fleet will still be operational for more 

than 20 years. Many of the components in these 

systems are already obsolete and will not be supportable in the future. There must be a coordinated effort to look across these radar systems, and 

develop replacement systems and support processes that are affordable and supportable for the projected operational life. 

Another focus area is applicable to all RF systems, not just radars. The Navy has been a leader in dealing with electromagnetic interference 

(EMI) and electromagnetic compatibility (EMC) 

given the close proximity of large numbers of RF 

systems. In the past, the primary tool was simple 

spectrum coordination and management. However, with most new major radar systems being developed at either 3 or 10 GHz, it will be difficult to 

solve EMI/EMC issues using this technique. With 

the exponential growth in demand and reliance on 

wireless telecommunications, the RF spectrum is 

becoming increasingly crowded, especially in developing areas of the world. This is compounded for the Navy since a significant portion of the 

world’s population live in coastal areas. Thus, there 

is an increasing demand and opportunity for S&T 

investment in spectral noise reduction, innovative 

spectrum sharing, and management techniques.

Summary

The future for radar systems presents many 

challenges. These challenges go beyond the traditional pursuit of increased functionality and 

performance, and require rigorous systems engineering and technology investments focused on 

solutions that benefit more than a singular radar 

system. The Technical Authority and the Radar 

TWHs play a pivotal role by providing an independent review of individual system developments; establishing and coordinating standards, tools, and 

processes; and helping identify critical focus areas 

that will help develop, field, and support the radar 

systems that the Surface Navy needs.