iii

TABLE OF CONTENTS

Page

Executive Summary v

I. Introduction 1

II. Background Assessment for X-Band AESA Radar 2

III. Family of Airborne Radars 10

IV. Findings and Recommendations 35

Appendices

A. Terms of Reference and Task Force Members A-1

B. Air Defense Assessment B-1

C. X-Band AESA Technology C-1

D. List of Acronyms D-1

v

EXECUTIVE SUMMARY

The Defense Science Board Task Force was formed to address questions related to the

development of X-band, active, electronically steered arrays (AESAs) for airborne

platforms. Areas focused on were advanced radar capabilities for ground targets and air

targets.

The airborne radar inventory can be divided into three broad categories:

(1) Air target surveillance and cueing radars mounted in rotodomes (e.g.,

AWACS, E-2C).

(2) Nose-mounted fighter radars for air and ground targets (e.g., F-15, F-16,

F-22, JSF).

(3) Side-looking radars for ground reconnaissance, surveillance, and cueing

(e.g., U-2, JSTARS, Global Hawk).

Categories (2) and (3) are dominated by X-band radars; the insertion of AESA

technology into category (3) was the primary subject for this task force.

The focus of airborne AESA technology is clearly aimed at fighter-class radars. At this

time the DoD has plans to build AESAs for the F-22 (331 units), the F/A-18E/F (258

units), the F-15C (18 units), the F-16-UAE (80 units), and the JSF (about 3000 units).

Raytheon (radar supplier for the F-15 and F-18) and Northrop Grumman (radar supplier

for the F-22 and F-16) are the dominant U.S. contractors in this market. The very large,

potential JSF procurement is in the competition phase, with Raytheon on the Boeing

team and Northrop Grumman on the Lockheed Martin team. This procurement, which

would extend through 2020, would require approximately 3.5 million transmit/receive

modules, which is roughly 80% of the projected fighter market. These AESA fighter

radars, in addition to air-to-air modes, support ground-surveillance for stationary and

moving targets, i.e., SAR and GMTI.

The potential AESA, side-looking airborne radar market is much smaller and more

speculative, viz., for the JSTARS (5 units  RTIP, Radar Technology Improvement

Program), for the Global Hawk (10-50 units), for the U-2 (2-17 units), and for the NATO

ground surveillance requirement (uncertain number of units). The proposed RTIP,

Global Hawk, and U-2 programs would require less than 250,000 transmit/receive

modules total, which is about 5% of the projected fighter radar market (or about 20% if

JSF is excluded). The surface-based X-band AESA market is dominated by Raytheonsupplied products for ballistic missile defense and air defense, viz., THAAD (tactical

missile defense) and GBR (national missile defense) on land, and MFR (multifunction

radar) and HPD (high-power discrimination) on ships. The projected requirements for Xband transmit/receive modules for surface-based radar is substantial, but very

speculative; rough projections for the next 15 years suggest the total surface market will

be one to two million modules, which is about one-third the size of the projected airborne

market. If JSF is excluded, the air and surface markets are comparable.

The Task Force found that the state of the art in airborne X-band AESAs has moved

impressively in the last decade due to several prototyping efforts and the JSF Dem Val

technology push. Factors of 3 to 5 or more in weight and cost reductions can be

supported along with innovations in mechanical design to simplify manufacturability and

maintenance. Transmit/receive modules are approaching commodity status, albeit with

limited component suppliers. Each contractor has been motivated to follow the family-of-
vi

radars construct to remain cost competitive. In all cases, components are being shared

among various products, and in many cases, complete subsystems (in both hardware

and software). For a given size and weight, AESA technology provides a factor of 10-30

times more net radar capability than competing approaches due to power increases,

lower losses, and increased flexibility. Also, AESA designs provide inherently superior

countermeasure resistance, enhanced range resolution (for target identification), and

more flexibility to support nontraditional radar modes such as jamming and ESM. In

addition, AESA technology supports high reliability/low maintenance designs with the

promise of attractive life cycle costs. These advantages are so compelling that it is

unlikely that any new U.S. fighter radar will be procured in the future without AESA

technology.

It is the assessment of the Task Force that the technology of X-band AESAs is mature

and ready for insertion, with little risk, into the existing ground surveillance radars on

JSTARS (i.e., RTIP), the U-2 (i.e., ASARS Improvement Program), and Global Hawk. In

the JSTARS and U-2 situations, we recommend that the technology follow a phasedinsertion schedule starting with the AESA hardware being inserted into the radar system

with minimal changes to the software and operating modes, i.e., the radar operates

essentially as in the past, but with the “ether-to-bits” part of the radar changed to an

active array of transmit/receive modules replacing the central power tube and passive

array. (The AESA hardware installation alone will generally result in a factor of 7 to 10

improvement in sensitivity due to higher power and lower losses.) Estimates are that as

little as 10% of the current radar software would need to be changed to accommodate

AESA insertion. The new modes to exploit the capabilities of the AESA should then be

phased in via a spiral approach to control development and testing costs, and reduce

risks. Based on this approach of AESA hardware insertion followed by evolutionary

software upgrades to exploit the new hardware, the Task Force recommends that the

current radar system providers, i.e., Raytheon for the U-2 and Northrop Grumman for the

JSTARS, be the lead contractors for these AESA upgrades.

The Task Force strongly supports the development of an X-band AESA for the Global

Hawk in the near term. The Global Hawk, with modest prime power upgrades, can

support an AESA radar that will provide excellent ground surveillance capability (SAR

and GMTI) in the high-flying, long-endurance, unmanned mode, which is highly

complementary to JSTARS. In addition, Global Hawk, with this radar technology, can

provide significant capability against conventional (and modest signature reduction) air

vehicles in the surveillance role for no-fly zones and drug enforcement; and in the role of

supporting the fire control for over-the-horizon intercepts (frequently referred to as

“ADSAM”  air-directed surface-to-air missile). We strongly support the development of

Global Hawk for the two roles to decrease the load on the AWACS and JSTARS fleets,

the so-called high-demand/low-density assets. A properly equipped Global Hawk fleet

could potentially handle most of the non-hot war demands and could supplement the

AWACS and JSTARS fleets in wartime situations.

The Terms-of-Reference for this Task Force requested a review of the National activities

on Advanced Air Defense with an emphasis on theater cruise missile defense.

However, the Defense Department focus on RTIP issues resulted in the Task Force

spending most of its short tenure on surface-surveillance issues. The Task Force

strongly supports the objective of meeting the land-attack cruise-missile threat by 2010.
vii

In the limited time spent on air defense, a brief assessment of progress in Advanced Air

Defense was done and a summary is provided in Appendix B. The Task Force identified

a critical need for increased attention to the systems engineering of intra- and interService theater-air-defense activities; a review of security issues is recommended to

help facilitate this systems engineering. References for a number of recent cruise

missile defense studies are provided in Appendix B, including the report of a National

Cruise Missile Defense Study which was in progress during the duration of this Task

Force.

The Task Force spent considerable effort in addressing the family-of-radars issue and

the way in which various approaches might affect the industrial base. The Task Force

supports the family-of-radars concept and observes that each contractor is motivated to

support such an approach to remain innovative and cost competitive. An important point

is that the family concept is contractor based and derived from their fighter radar

programs, which, as was previously illustrated, dominate the airborne X-band AESA

business. The side-looking airborne business is much smaller and rides on the

hardware and software technology advances in the fighter lines. Based on their robust

fighter work, and in particular, the JSF technology development, and their experience

base with the U-2 and JSTARS, the Task Force judges both Raytheon and Northrop

Grumman are well equipped to compete in the hardware and software aspects of the

side-looking AESA radar business.

The Task Force unanimously recommends the following for the JSTARS, U-2, and

Global Hawk fleets:

1. JSTARS, U-2

Switch from passive-array/centralized-transmitter hardware architectures to

AESAs in production of new radars to meet future requirements. New software

modes to exploit the AESA capabilities should be phased in an orderly fashion in

coordination with other evolutionary upgrades in the software.

In the JSTARS fleet, we recommend equipping aircraft number 16 (which is in

long-lead procurement phase) with the AESA hardware rather than the old

design. Any new JSTARS aircraft beyond number 16 (if built) would carry the

AESA; the final fleet size would determine whether any retrofits are needed to

meet the requirement for five RTIP aircraft. This approach has savings in the

billion-dollar class (substantially because old technology tubes and passive

arrays are not installed and then removed later to insert AESAs) and makes the

RTIP aircraft available three to four years sooner (a year or two ahead of the

desired 2010 date instead of two years late).

For the U-2, we recommend the two additional radars being considered be built

with AESA hardware insertions rather than with the old design, which uses a

passive array and tube transmitter; enhanced modes should be used to exploit

the AESA capabilities in the spiral mode discussed for JSTARS. Retrofits of the

old radars with AESAs, if any, would be done according to program needs.
viii

2. Global Hawk

Conduct a competition to supply an X-band AESA for the Global Hawk fleet with

requirements for ground targets (SAR, GMTI) and air targets (surveillance and

fire control). A very desirable acquisition approach would include fly-offs

between the two most qualified teams.

The government should coordinate requirements across the fighter,

intell/reconnaissance, and wide-area surveillance communities to facilitate the

family-of-radars coupling.

The Task Force believes the preceding recommendations provide a timely and costeffective plan for JSTARS RTIP; provide a plan to bring next-generation ground

surveillance capability to the U-2 and Global Hawk; and establish an air-target role for

Global Hawk to help offset the extreme demands on AWACS. These recommendations

will also help maintain a competitive U.S. radar industrial base that will be well prepared

to compete in NATO and other international markets.
1

I. INTRODUCTION

The broad motivation for this Task Force arises from the need to consider advanced,

side-looking radar technology for the JSTARS, U-2, and Global Hawk platforms. The

side-looking radars on these platforms have the primary role of locating ground targets in

the reconnaissance/intelligence role and/or in the surveillance and cueing role during

military operations. In the case of the new Global Hawk platform, consideration is being

given to the use of its radar for surveillance and cueing of airborne targets (to

supplement AWACS) in addition to ground target capabilities.

After many years of component research and prototype system development, the last

decade has seen X-band (10 GHz+) active electronically scanned arrays (AESAs)

emerge as a mature technology that competes to replace other options for the power

source and the antenna architecture. Two prominent early programs in X-band AESA

technology development have been the Army family-of-radars program (which provided

the basis for the X-band AESAs in the THAAD and GBR radars for theater and national

missile defense systems, respectively), and the Air Force programs to produce X-band

AESAs for the F-15 and the F-22. The investments in JSF radar technology have also

fostered pivotal advances in reducing cost, weight, and mechanical complexity. JSF

transmit/receive (T/R) modules are referred to as “fourth generation” T/R module

technology.

The specific trigger for this Task Force concerned developing the preferred strategy for

inserting AESA technology into JSTARS, including issues of timing, competition versus

teaming approaches, and family-of-radars concepts and their meaning and applicability.

This Task Force met over a one-month period in a highly focused format to meet the

decision schedule requested to support the FY02 budget cycle. All Task Force

members had radar technology backgrounds and/or program-related experience to the

topic at hand, so it was able to meet the required schedule.

Section II provides background material on X-band AESAs. Section III addresses the

Global Hawk, the U-2, and the JSTARS RTIP. The findings and recommendations of

the Task Force are presented in Section IV.

Appendix A includes the Terms of Reference, the Task Force member list, and a

summary of the briefings received. A summary review of advanced air defense progress

is given in Appendix B. In Appendix C, additional material is provided on AESA

technology and future research directions, and Appendix D contains a list of acronyms.
2

II. BACKGROUND ASSESSMENT FOR X-BAND AESA RADAR

SYSTEMS AND RADAR VENDORS

(X-band AESAs - High Power Density)

Fighters Raytheon Northrop Grumman

F-15 V-2 - (18 units) F-22 - (331 units)*

F-18 E/F - (258 units) F-16 UAE - (80 units)

JSF - In competition JSF - In competition

Surface THAAD (10 units)

XGBR (1 + ?)

MFR (?)

HPD (?)

Others: MEADS (Lockheed Martin, et al.)

______________________________________

*Raytheon is a major subcontractor

The fighter AESA market has Raytheon and Northrop Grumman as the primary

competitors. Since Hughes and Texas Instruments (both now Raytheon) were involved

in the F-22 radar, there is significant Raytheon participation in the F-22, although

Northrop Grumman is the lead. The JSF competition, which has potentially 3000 or so

units at stake, is the dominant factor in the future fighter market. The advances in Xband AESA technology are such that it is unlikely that any new U.S. fighter radar will be

built without an AESA. (Additional discussion of X-band AESA technology and

performance are given in Appendix C.)

The surface-based X-band AESA market is dominated by Raytheon. In the 1980s the

Army developed a family of X-band radar concept for use in theater and national missile

defense systems. Raytheon won the competition for this "family" and produced the early

versions of the THAAD radar in the mid-1990s, viz., an approximately 10 m2 AESA

containing about 25,000 T/R modules. A prototype national missile defense radar

followed and has been in operation at Kwajalein Missile Range for several years; this

radar is an AESA with about a 100 m2 aperture and contains about 17,000 modules (i.e.,

is partially filled). A portion of the Kwajalein radar T/R modules was previously used in

THAAD, providing a demonstration of the family-of-radars concept at the module level.

Raytheon won the Navy competition for the multi-function radar (MFR) based on an Xband AESA design. This radar, which is in the prototype stage, has about 5000 T/R

modules (somewhat over 1 m2 aperture). The concept is for a three-faced arrangement

to cover 360o around the ship; the potential market is several hundred ship sets. The

high-power discrimination (HPD) radar is a ship-based, X-band, AESA radar to support

Naval capability in ballistic missile defense; this radar is in the early prototyping stage

and is based on THAAD technology. The aperture size is 6.5 m2 (about 16,000 T/R

modules).
3

The MEADS surface-to-air missile system includes an X-band AESA fire control radar.

Lockheed Martin is the prime contractor, with Germany and Italy as partners. The T/R

modules are being manufactured in a work-share agreement among the partners with

chip fabrication in the U.S., module integration in Germany, and module testing in Italy.

X-band AESAs are also being developed for the aerostat (JLENS Program  Raytheon)

and satellites (Discoverer II Program  Raytheon and Northrop Grumman competing).

However, because on aerostats and satellites power is at a premium and aperture size

is less constrained, these designs tend to be low-power density concepts rather than the

high-power density designs for fixed wing aircraft and surface use.

The U.S. X-band T/R module production capacity as presented to the Task Force was

stated to be roughly two-thirds Raytheon, one-sixth Northrop Grumman and one-sixth

other (including Lockheed Martin and M/A-COM). As concerns coupling to the

commercial community, of the 11,000 wafers processed in the Raytheon gallium

arsenide foundry (Andover, Mass.) this past year, only approximately 400 (3.6%) were

for the military, and of those fewer than 200 (<2%) were for military radar. Once a

foundry has matured a given chip-producing process, the chip designs may vary for

various modules (e.g., airborne versus surface use) but the same underlying foundry

process is employed for chip production. The complexity and level of integration in T/R

module chips is very high compared with routine commercial-run chips.

In the international area, the Dutch company SIGNAAL has built two prototypes of an Xband AESA for ship defense. This radar has a less than 1 m2

 aperture (about 3000 T/R

modules) and uses relatively low-power SIGNAAL T/R modules.
4

RADAR ARCHITECTURES

Power Source Antenna Beam Scanning

Centralized Reflector Mechanical

Centralized Passive Array Electronic

Distributed Active Array Electronic

Active Electronically Steered Arrays (AESAs)

By the 1990s, after more than 25 years of R&D, active arrays at X-band

have become viable production candidates for wide-scale use in surface

and airborne radars.

Led by fighter radar needs in the air and by ballistic missile defense and air

defense needs on the surface, the X-band AESA market is very active.

High-frequency radar (for surface and airborne use) was developed during World War II

using centralized power sources, e.g., the magnetron, and reflector antennas. By the

1960s, motivated by the strong desire for electronic beam control in such missions as

ballistic missile defense, space surveillance, and air defense, passive array technology

was rapidly maturing. The Patriot and AEGIS air defense radars are large production

examples of passive arrays; the JSTARS radar is based on the mid-1980s state of the

art in passive array technology.

Although passive array technology provides electronic beam control, it has the

disadvantage that phase control must be accomplished at high power to position the

transmit beam. High-power phase control technology is dominated by power loss

concerns. Typical total losses in early systems resulted in a factor of 10 reduction in

radiated power; in modern systems these losses are still in the factor of 5 range.

The active array concept has the planar antenna face populated by discrete elements

referred to as transmit/receive modules (T/R modules). In an active array the power

source is now distributed and phase control to provide electronic beam steering can be

accomplished at low power (and with only minor losses). Since large numbers of T/R

modules can be required, viz., 3000 - 4000 per square meter, module cost has always

been a primary concern with active arrays.

After many years of technology investment, by circa 1990, X-band active arrays arrived

as serious contenders in the radar market. Pivotal developments along the way included

improvement of gallium arsenide material and the development of monolithic microwave

integrated circuit (MMIC) technology. MMIC technology uses lithographic-type

processes to produce microwave circuits on chips at very high levels of integration. A

modern X-band T/R module, in addition to a radiating element, will contain five to seven

chips (MMICs) produced in a foundry and later integrated into a substrate with a few

discrete components and cooling provisions, all filling a space on the order of 1/4 in3.
5

High-power radar applications, such as fighters and JSTARS RTIP, use "filled"

apertures, which at X-band is generally about 3000 modules per square meter of

antenna. Fighter radars are usually in the 1000 to 2000 modules size range. Modules

that are readily available have peak powers of about 10 W with average power of about

2 W; hence, for a square meter of filled X-band aperture the peak power is typically 30

kW and the average power about 6 kW.
6

PROJECTED AIRBORNE RADARS

(X-Band AESAs)

The data in the table indicate the planned radar unit buys as a function of year. The

F-22, F/A-18E/F, F-15C, and F-16 UAE programs have firm commitments to

development and production although the final number of units is very likely to change.

The potential very large JSF buy is, of course, tied to the vagaries of the airframe

program. For JSF, Raytheon is providing the radar for the Boeing team and Northrop

Grumman for the Lockheed team. Clearly, the current “winner-take-all” procurement

strategy could have significant ramifications in the X-band AESA industrial base.

The two side-looking radars on the list are the Global Hawk and the JSTARS RTIP. The

RTIP program shown follows the baseline DAB-approved program. The Global Hawk

numbers do not correspond to an approved program, but reflect a program concept

under discussion.

TO

FY: 2000 2005 2010 2013 COMPLETE TOTAL

F-22 - - - 10 16 24 36 36 36 36 36 36 36 29 - 331

F/A-18E/F - - - - - 8 12 22 48 48 48 48 24 - - 258

F-15C - 13 5 - - - - - - - - - - - - 18

F-16 UAE 5 10 10 10 10 10 10 10 5 80

JSF - - - - - - 10 22 61 88 108 154 194 194 2021 2852

GHAWK 4 4 4 4 4 4 4 4 4 12 48

JSTARS RTIP 0.75* 1 1 1 1 1 1 6.75

* Sub-scale Development Unit

 Total Modules 

F-22 496500

F/A-18E/F 283800

F-15C 27000

F-16 UAE 80000

JSF 3422400

GHAWK 96000

JSTARS RTIP 91125
7

THIS PAGE INTENTIONALLY BLANK
8

 AIRBORNE INTEL/RECON/SURVEILLANE/CUEING

(Side Looking)

ß Programs

- U-2

- JSTARS

- Global Hawk

- ASTOR

- NATO: NATAR or SOSTAR or ASTOR Derivative

ß The U-2, JSTARS, Global Hawk and ASTOR all currently employ Xband, passive array radars

ß The JSTARS RTIP (Radar Technology Improvement Program)

includes replacing the passive array with an AESA.

ß The NATO requirement for ground surveillance is targeted to a 2007

decision timeframe (platform/radar technology is undecided)

The side-looking radar programs shown all currently employ passive array technology.

As X-band AESA technology penetrates the side-looking market, the logical path being

considered is to employ as much commonality in the hardware and software as possible;

this approach has been referred to as a “family-of-radars.” Global Hawk, the U-2, and

JSTARS are each covered in some level of detail in the following section.

The United Kingdom’s ASTOR program is a business-jet-based, ground-surveillance

radar; this system employs a passive-array design. The contractor is Raytheon, and the

current plan is for five aircraft to be operational in 2007.

The NATO ground-surveillance program (referred to as “Alliance Ground Surveillance” –

or AGS) has been under consideration for some time and closure on the path to

procurement will not occur soon. A brief record of the AGS effort is given below, derived

from DoD briefings to the Task Force.

1992 AGS requirement confirmed.

1995 Validated that NATO should adopt a “minimum essential NATO owned and

operated core capability supplemented by interoperable national assets.”

1996 U.S. proposes “Fast Track” plan which offers six JSTARS aircraft for purchase.

1997 Fast-Track offer rejected; new approaches sought.

U.S. offers RTIP sensor for integration by NATO on a platform of their choice. A

study produces an RTIP-class radar on a mid-sized jet, but no consensus is

reached.

1999 The CNAD (Conference of National Armaments Directors) “welcomes” the

formation of:
9

1. An RTIP Group (NATAR-NATO Transatlantic Advanced Radar) to pursue a

two-year project definition phase based on RTIP. Nations involved include

Norway, Canada, Denmark, Belgium, Luxembourg, and the United States.

2. Newly formed SOSTAR Group to pursue technology development of a new

European sensor. Nations involved include France, Germany, Italy, and the

Netherlands. The scale of this project is $100M over five years to

demonstrate a radar that “will duplicate or slightly exceed” JSTARS

capability.

The NATAR and SOSTAR options are focused on procurement decisions that might

occur in the 2007 timeframe. The architecture and technology of the ASTOR system is

also expected to be proposed to compete with the NATAR and SOSTAR offerings. Of

course, the ground segment of AGS must also be decided upon; that subject is beyond

the scope of this discussion.

A major architectural choice in the airborne surface-surveillance platform is whether to

have on-board command and control, and, if so, to what extent. Clearly, the large

JSTARS aircraft utilizes most of its space for the extensive, on-board command-andcontrol capability. The fact that AESA technology permits much more radar in a small

package enables modest-payload aircraft to have significant sensor capabilities if little or

none of the payload is used for on-board command and control. The continuing

evolution of network-centric warfare is presenting favorable opportunities for sensor-only

platforms, viz., Global Hawk, in overall surveillance architectures.
10

III. FAMILY OF AIRBORNE RADARS

Modern fighter AESA radar technologies and family-of-radars concepts provide the basis

for the next generation of highly capable AESA radars for airborne surveillance systems.

The principal candidates for the applications of these technologies and concepts will be

the JSTARS RTIP upgrade, improved radars for the Global Hawk and U-2, and the U.S.

contribution to NATAR. A modular, scalar AESA approach will provide a common

framework for the development of a family of radars that can accommodate the different

size, weight, and power constraints of these platforms.

Broadly speaking, the future airborne surveillance platforms shown in the chart can be

divided into two classes, the commercial airliner/business jet class capable of carrying a

relatively large (18 to 24 ft) antenna, and the U-2/Global Hawk class, which is limited to

smaller antennas on the order of 6 to 10 feet. A modular, scalable radar architecture,

combined with a top level system engineering approach focused on addressing the radar

design for both these classes of platforms, provides the opportunity for minimizing

development costs, thus making an AESA, with its attendant benefits, an attractive

alternative to sensors on current platforms (JSTARS, U-2, and Global Hawk).

In the following sections AESAs for JSTARS RTIP, the Global Hawk, and the U-2 are

discussed. The potential benefit of an AESA upgrade for the Global Hawk is addressed

Active Array Radar Product Family Evolution

Raytheon

Northrop

Grumman

Future
11

in more detail than the others to illustrate the surface target capability (SAR and GMTI)

and air target capability that can be obtained from a modern X-band AESA.
12

Global Hawk is currently an ACTD (advanced concepts technology demonstration) that

has been undergoing evaluation over the past year. As a result of this evaluation,

Global Hawk has recently gained military endorsement by the U.S. Joint Forces

Command, which called for heavy involvement of the four existing Global Hawks in

training, exercises, and actual operations. The potential value of Global Hawk as a way

of coping with the high demand/low density (HDLD) problem has increased interest in

both accelerating the acquisition of additional Global Hawks, and in improving their

capabilities beyond those on the current ACTD units. The radar is a prime candidate for

such improvement.

The characteristics of the current “ACTD” radar are summarized in the chart. At the

inception of the program in 1995, this choice of design parameters was dictated by a

desire to minimize cost and risk, as well as allow both the radar and EO/IR unit to be

carried simultaneously. As a result the radar is limited in capability. It was primarily

aimed at SAR image collection, with GMTI added essentially as an afterthought. For

example, mechanical scanning in both azimuth and elevation preclude all but the most

basic GMTI search operation. The low power aperture product restricts the sensitivity to

relatively large cross-section targets, short ranges, or long revisit times in GMTI search

mode. The antenna length of about four feet, together with only two phase centers,

limits GMTI accuracy and clutter rejection performance (which limits the minimum

detectable velocity).

Replacing the current radar with an AESA will have a number of benefits which will be

discussed in the following charts. As a basic measure of this improvement, a gain in the

power aperture product by about a factor of 10 can be realized by an AESA when

coupled with a modest increase in prime power available to the radar.

Current Global Hawk Program

ACTD Radar

4.1 x 1.2 ft. Mechanical Scan Antenna

350 W Average Power

6600 W Prime Power to Radar

2 Channel Receiver

Poor GMTI Accuracy

SAR Radar with GMTI as afterthought

Factor of 10 to 20 Less Power

Aperture than AESA Upgrade

FY 00 01 02 03 04 05 06 07 08 09 10

Block 5 Production 2/Year

EMD Block 10 EMD / Sigint EMD

Block 10 4/Year

ESA EMD ?

* MS II * MS III

Global Hawk Sensor Payload
13

The currently planned program is summarized at the bottom of the chart. It is suggested

that the addition of an AESA be part of the Block 10 upgrade, including power

generation modifications to supply 20-30 kW of prime power to the radar.
14

The potential for increasing the capabilities of Global Hawk by replacing the current

radar with a more capable, electronically steered array has been addressed in a number

of earlier studies. The 1998 Airborne Radar Study∗ considered a number of options,

including some that required modifying the current airframe to get significantly more

payload capacity (the so-called “Global Truck” option). Subsequently there have been

numerous and ongoing studies by various organizations to explore additional design

options reflecting the progress in fighter active array technology and scalable, modular,

open architecture approaches. To illustrate the potential benefits of an AESA on Global

Hawk, the Task Force selected the point design described in the chart.

The primary objective of this point design was to achieve high performance GMTI

ground surveillance for moving targets, and high quality SAR for ground imaging and the

detection and classification of non-moving targets. In addition, the radar includes air-toair modes (surveillance and targeting) consistent with modest prime power upgrades to

provide on the order of 20-30 kW prime power to the radar. This power requirement is

based on a relatively conservative overall T/R module efficiency of 15%. Progress in

module development can be expected to lead to improved module efficiencies, which

would either further reduce the prime power requirements or result in increased radar

performance.

 

∗

 Airborne Radar Study, Executive Summary Briefing to USD(A&T), 3 March 1998

Global Hawk AESA Point Design

Objectives - High Quality GMTI/SAR as First Priority

- Air to Air Performance Consistent with Modest Prime Power

Upgrade

Assumptions - 20-30 KW Radar Prime Power

- Internal Carriage Limits Antenna Length to ~7.5 Feet

- Conservative Technology Assumption @ 15% TR Module Efficiency

Design - 7.5 x 1 foot Aperture

- 2.5 to 4.5 KW Radiated Average Power

- 4 Simultaneous Receive Beams

- 5 Receiver Channels

- Interleaved SAR/GMTI Modes

- High Range Resolution (HRR) Modes for Target Classification

Performance - Scan JSTARS GRCA in 30-40 Seconds

(Comparable to JSTARS now)

Note - Horizontal Aperture 3-4 Times Smaller than JSTARS/RTIP

- Poorer Angle Accuracy will Impact Some Military Desires

(e.g., Targeting for Long Range ATACMS)
15

For improved GMTI performance, it is desirable to increase antenna length as much as

possible to lower the minimum detectable velocity (MDV). Platform constraints limit the

antenna length to 7.5 ft unless significant changes are made to the platform itself. GMTI

performance is further enhanced by partitioning the array into multiple phase centers

(subarrays) with individual receive channels and analog to digital converters (A/Ds)

providing data from multiple channels to the signal processor. Multiple receive channels

also provide a more robust ECCM capability. Both these benefits are realized through

space-time adaptive processing (STAP), enabled by the multichannel radar data and an

on-board digital signal processor. The capability to provide (a selectable number of)

multiple simultaneous receive beams can be exploited to trade excess sensitivity at

shorter ranges for increased area rate/coverage for both SAR and GMTI.

An AESA, by virtue of its inherent rapid steering capability and the ability to support wide

bandwidths and waveform diversity, provides the opportunity to use the radar in a variety

of distinct or interleaved modes. An example is interleaving SAR and GMTI where a

high bandwidth (SAR) waveform may be intermixed with a lower bandwidth (GMTI)

waveform. Another example is the use of high range resolution (HRR) waveform mode,

which provides data for aided target recognition of moving targets. Clearly, fully

exploiting this flexibility raises challenges in both the signal processor and radar

resource scheduler/controller. However, with an open system architecture and modular

approach, an evolutionary path toward achieving progressively more capability is

provided without the need to redesign/rebuild the AESA (the “ether to bits” part of the

system).

For reference purposes, the search time for a nominal JSTAR GRCA (ground reference

coverage area) is shown to be comparable to that of the current JSTARS. Because the

antenna is significantly shorter than that of JSTARS, GMTI MDV performance as well as

position accuracy will not be as good as that provided by JSTARS, which may impact a

single Global Hawk’s ability to support targeting at long ranges for certain weapons

(without autonomous homing capability). However, as discussed later, multiple Global

Hawks may be used to improve accuracy by multilateration.
16

The addition of an AESA with the characteristics described in the previous chart can

improve not only Global Hawk’s ground surveillance (SAR and GMTI) capability, but add

a very capable air-to-air mode for conventional targets. The air-to-air mode includes

autonomous search, e.g., used in no-fly zone enforcement, as well as cued search and

fire control support on selected targets. This latter capability can provide over-thehorizon targeting support for conventional targets with suitable surface-to-air missiles,

also referred to as air directed surface-to-air missiles (ADSAM) engagements. Potential

ADSAM capabilities of a Global Hawk equipped with the AESA point design are

illustrated in a subsequent chart.

Rapid beam agility also allows interleaving various modes as illustrated in the chart, so

that a combination of these modes can be exercised, depending on mission needs. To

do so will, of course, require the software that can take full advantage of AESA

capabilities. Phased introduction of this software can be used to add capabilities,

starting with the current ground surveillance modes, but with greatly improved

performance.

Global Hawk

MULTI-MISSION ISR

Air-to-Air 

Range (cued) 

SAR 

 

Data Link

Air-to-Air 

Search/Track 

 Data Link

GMTI
17

Another example of leveraging the added flexibility provided by an AESA is illustrated by

the application to aided moving target tracking and recognition. For these functions a

high range resolution (HRR) waveform is used to collect data on selected targets of

interest to provide a range profile, or “1-D image,” of these targets. To optimize the

benefit of range profiles, it is desirable to collect HRR data when targets are at favorable

aspect angle (i.e., away from broadside). The HRR data collection is scheduled based

on the GMTI track, and multiple targets in diverse locations can be revisited rapidly

taking advantage of the AESA beam agility. If a target is to be tracked in a dense target

environment, the HRR waveform may also be used to provide additional characterization

of the target using range profile data to help distinguish it from “

be difficult to separate based only on kinematic measurements and tracks.

Leveraging AESA Capabilities 

High Range Resolution (HRR) Example

• Selects waveform to collect HRR data on specific 

targets interleaved with normal GMTI waveforms

• Compares to a database of HRR range profiles of 

targets of interest (e.g. TEL) for best matches 

• Multiple revisits at different aspect angles (based 

on GMTI track) to enhance confidence

0 0.51924192 0.51924192 0.5

0 0.46110416 0.46110416 0.5

0 0.11008026 0.11008026 0.5

0 0.84051027 0.84051027 0.5

0 0.81389813 0.81389813 0.5

0 0.3094882 0.3094882 0.5

0 0.34626301 0.34626301 0.5

1 0.85219886 1.85219886 0.5

0.5 0.4247261 0.9247261 0.75

0.5 0.11926634 0.61926634 0.8

2 0.24970244 2.24970244 0.6

3 0.3640553 3.3640553 3.5

1 0.56035035 1.56035035 3

5 0.68511002 5.68511002 1

1.5 0.6753441 2.1753441 5

HRR Range Profile

0

1

2

3

4

5

6

0 5 10 15 20 25 30

Range(m)

Amplitude

Target

Template

GMTI

HRR
18

The figure indicates the comparative performance of the current Global Hawk radar and

the extended range and additional air-to-air modes achieved with the point design

AESA. In the GMTI ground surveillance mode the increased power aperture enables

longer ranges and shorter revisit times, illustrated by the region labeled “GMTI GRCA”.

The added sensitivity and beam agility enables cued search and fire control support

(e.g., tracking of multiple targets at high rate) in the air-to-air mode. Autonomous

surveillance of a 90 deg sector can be carried out against a conventional aircraft (~3 m2

radar cross section) to a range of about 230 km, with a scan time of 10 sec. A cued

search in combination with precision tracking of a number of targets (~10) can be carried

against the same class of targets to a range of about 300 km. While these values will

vary with different assumption on targets, operational modes, and specific AESA design,

they provide a general measure of increased capability afforded by an AESA for Global

Hawk.

AESA Enables Extended Range Operation

GMTI

GRCA

Scan time ~ 30 sec

Current Global Hawk GMTI Search Region

Scan Time = 120 sec

Air-to-Air search

Scan Time = ~10 sec

Air-to-Air cued search and

fire control support

200 km
19

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20

Global Hawk with an AESA with the power and aperture assumed for the DSB point

design could be used in various mission roles. The coverage provided by such a system

for two potential mission areas is illustrated in the chart: ground surveillance during

peacetime and autonomous air surveillance, e.g. to monitor no-fly zone enforcement.

These two applications address the HDLD problem by providing an alternative to the use

of JSTARS and AWACS to perform these missions. The high endurance, unmanned

operation, wideband data links, and remote basing also lead to much reduced

infrastructure demands. In times of war, the Global Hawk would be more tightly

integrated into the battlefield command-and-control infrastructure, possibly via interfaces

to, for example, JSTARS in a “hen-and-chicks” concept, which is discussed further later

in the report.

To provide a context for the potential Global Hawk capabilities in these mission

applications, the preceding charts show the coverage achieved in two regions of tension,

Southwest Asia, encompassing the no-fly zone in southern Iraq, and Korea. A brief

discussion of each application follows. In all cases the DSB point design AESA is

assumed.

Global Hawk AESA Capabilities

DSB Point Design
21

Ground surveillance: Global Hawk can provide ground surveillance of ground moving

targets (nominally 10 m2 cross section) out to a range of about 250 km. The chart shows

a notional deployment of two Global Hawks providing wide-area ground surveillance

over regions in both geographic areas that provide wide buffer zones at the borders of

Iraq and North Korea, which would enable monitoring any large scale military force

movements (GMTI) and force buildups (SAR) that would constitute a threat. The

assumed revisit time of 75 sec is adequate in this case since the interest is in detecting

and tracking major military forces deploying to the border region, rather than tracking

and targeting individual targets. Note also that since Global Hawk flies at much higher

altitudes than JSTARS, terrain obscuration is less severe, an important benefit in

mountainous terrain typical of the Korean region.

Air-to-Air Surveillance: The principal criterion underlying the DSB strawman point design

for a Global Hawk AESA was to provide a robust ground surveillance capability. Given

such a capability, the question was to what extent the AESA could support other mission

areas by exploiting the inherent flexibility in waveform selection and radar control. One

very important area considered is autonomous surveillance of the air space in no-fly

zones (southern Iraq) or other areas of heightened interest during peacetime (e.g., North

Korea near the border with South Korea). Because of the limit on power and aperture,

Global Hawk would be most useful against larger, “conventional” aircraft with radar cross

section on the order of 3 m2 (5 dBsm). For these missions it is also not critical to have

very short frame times. In the DSB analysis a frame time of 30 sec was assumed,

together with a search volume extending over a 90 deg sector and from an altitude of 60

kft to the ground. With these assumptions, the Global Hawk can search out to a range

of about 300 km. The second set of maps in the previous chart illustrates the coverage

achieved using two platforms nominally stationed as shown. In the case of North Korea,

these two platforms could completely cover the area near South Korea, including

substantial regions over water that might serve as approach routes to South Korea.

In the example for Southwest Asia, two Global Hawks would cover a substantial portion

of, but not the entire no-fly region. Additional platforms could be used to obtain greater

coverage. However, if overflight of Iraq and other unfriendly territory is to be avoided,

the range limitation would prevent total coverage of the region. The lower cost and

higher altitude of operation combined with a modest level of self-protection, and the fact

that no human lives are at stake makes overflight of Iraq an option if the situation

demands it. In such a case several Global Hawks could provide a level of complete and

continuous coverage not practical, even if possible, with the current high-valued,

manned AWACS.

Finally, the potential air surveillance capability of Global Hawk could be quite helpful in

reducing the demands on AWACS for counter-drug surveillance. The high range

resolution waveforms in the X-band AESA also provide a significant source of noncooperative identification information.
22

The previous two applications of an AESA-equipped Global Hawk were directed at

satisfying key operational needs during peacetime and to cope more effectively with the

HDLD problem than is possible with current assets. During wartime, an additional

capability can be exploited  support of ADSAM engagements against airborne targets

with modestly low radar cross section, representative of many of today’s threats. The

essence of the ADSAM concept is that the surface based magazine is to be utilized to its

full kinematic range for low altitude targets. For those low altitude targets below the

horizon of the surface based sensors, the airborne partner provides the needed

surveillance and fire control data. Both sea- and land-launched SAMs could be

supported, thereby adding to the depth-of-fire of magazines already in the force. Typical

low altitude target horizons are 15 to 30 Km. These horizons are factors of 5 to 10

shorter than the kinematic range of Patriot and Aegis missiles. For lower cross-section

targets, such as on the order of 0.1 m2, this coverage is reduced by a factor of 2.

However, the notional deployment of two Global Hawks together with two Aegis ships for

the Korean example shown in the chart would provide broad coverage to distances

greater than ~50 km behind the border into North Korea. If warranted, Global Hawks

could be added, or deployed further forward, to extend their reach into enemy territory.

The potential benefit of forward deployment is discussed in the next section.

Global Hawk AESA Capabilities

DSB Point Design
23

Any AESA on Global Hawk will have substantially lower power aperture than a radar on

a large manned aircraft. The significantly lower cost and unmanned nature of Global

Hawk present the opportunity to shorten the standoff compared to, for example,

JSTARS. (Note that one of the attributes of Global Hawk was to be that it is “

although there is no generally accepted agreement on what exactly is meant by that. An

AESA equipped Global Hawk should cost about what an F-16 costs; JSTARS costs

about what 6-8 F-16s cost.)

The potential shorter standoff of Global Hawk decreases the range to a target and thus

increases the “effective” radar power aperture. The figure shows the relative location

required for Global Hawk to have similar performance to a larger platform with an

antenna aperture about six times larger in area. The assumption in this figure is that

both radars are based on the modular, scalable family-of-radars concept, i.e., that the

aperture power density is the same for both. This assumption implies that the power

aperture for Global Hawk is about a factor of 40 lower than that for the large antenna.

The reason that closer standoff is needed when tracking compared to searching is that

to maintain tracking cross-range accuracy requires additional range compensation for

the larger beam from the shorter aperture length.

Standoff Considerations

24 ft

2 ft

1ft

7.5ft

Tracking Sector Search
24

By virtue of its satellite communication links and direct downlink, Global Hawk is capable

of operating independently from other surveillance assets. This situation is likely to be

the normal use of Global Hawk. However, during times of tension and war, Global Hawk

could be integrated with a manned platform such as JSTARS. In this “hen and chicks”

concept, the Global Hawks are integrated into the overall ISR command-and-control

structure to effectively augment JSTARS. In pre-hostilities this augmentation may be

used to extend the JSTARS coverage as indicated in the figure. Shorter standoff of

Global Hawk can further its reach and increase its performance.

Closer range

Better aspect

Multi- lateration for

Precision Targeting

of Moving Targets

Stand-off

Improve detection and location

“Hen-and-Chicks” Architecture

Expanded Surveillance Coverage

JSTARS “GRCA”

Stand-off

GH 1 “GRCA” GH 2 “GRCA”

GH 1 GH 2

JSTARS
25

In time of war the “hen and chicks” concept may be used to take advantage of shorter

standoff Global Hawks and the geometric diversity offered by multiple platforms to

support both deep reach and precision targeting. In this case the ability to get

multilateration data on a target of interest, as well as simultaneous views of the target

from different aspect angles, can help in target recognition and precision target location.

The DARPA AMSTE (affordable moving surface target engagement) program relies on

such multilateral measurements to achieve the needed accuracy for low cost precisionguided weapons.
26

The U-2 is a major ISR platform with a diverse set of sensors, including radar, EO, and

SIGINT sensors. It has been in operation for many years and has demonstrated its

value in numerous missions during that time. Its radar capability focused primarily on

radar imaging of ground scenes, including stationary targets, using the advanced

synthetic aperture radar system (ASARS). The original ASARS was a mechanically

steered array that represented a cost-effective solution to satisfying the beam agility

requirements for SAR image collection, which typically necessitates relatively long dwell

times to collect the data for high resolution imagery. (The U-2 SAR imaging capabilities

have recently been declassifiedthey range from 3 m for low resolution strip maps to 1

ft resolution for spot mode.) In 1996 the ASARS improvement program (AIP) was

initiated which replaced the radar with an improved version, referred to as ASARS-2.

These improvements are aimed, in part, at adding to the U-2 the capability to detect and

track moving targets. In particular, ASARS-2 has a 1-D electronically steered array that

provides beam agility in azimuth, allowing rapid beam switching for tracking multiple

targets as well as interleaving various radar modes. It is a passive array, similar in

concept to the JSTARS 1-D passive array, i.e., radar power is provided by a high power

central (tube) transmitter and is distributed to the array columns via a microwave power

distribution network (for more discussion on passive vs. active ESAs see Appendix C).

• 1-D Passive ESA 

• Strip SAR

• Spot SAR

• GMTI

• 10 U-2s currently equipped with

ASARS-2

• 2 additional units to be equipped as 

part of program 

U-2 ASARS Improvement Program

ASARS-2
27

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28

Global Hawk and the U-2 have a number of common system attributes. Both platforms

operate at high altitude (the U-2 can fly somewhat higher) and are generally addressing

similar operational needs. Also, for both platforms tasking, exploitation, and command

and control are performed off-platform. Hence, on-board processing and sensor data

link requirements can be expected to be similar. While differences in payload capacity

allow the U-2 to carry more sensors simultaneously, the size, weight, and power

constraints for the radar are sufficiently similar to make the family-of-radars concept

particularly attractive in jointly addressing the AESA design for these two platforms. Two

approaches are shown. In the first, the similarity between the two platforms and their

ground surveillance missions can be exploited to design an overall common system

architecture. The specific design of the AESA in this approach is optimized individually

for the space available for each platform within the framework of a modular, scalable

architecture and technology. This may be accomplished, for example, by suitably

defining antenna modular building blocks (e.g., subarrays) that can be used to assemble

different-sized antennas. Using the DSB point design for the Global Hawk AESA

discussed previously, a scaled-down AESA for the U-2 (to conform to length constraints)

would be ~2 dB lower in power aperture. This 2 dB reduction would result in a decrease

in range of about 10% for sector search, and about 15% for track. This decrease would

be approximately 20% for a fixed area search.

Family-of-Radars

Architecture and Technology

Optimize for

U-2

Optimize for

Global Hawk

Optimize for

Common AESA

• Maximize AESA capability

• Leverage modular/scalar architecture

 to reduce platform-unique costs

- Commonality in software, signal

 processing T/R modules, electronics

• Potential cost advantage

- Development and manufacture

- Operation and maintenance

• Power Aperture Product ~ 2 dB

 lower than DSB Global Hawk point design

AESA for U-2 and Global Hawk
29

The second approach shown in the figure is to develop a single AESA design for both

platforms. This approach may sacrifice some of the capability of Global Hawk that could

be achieved with an aggressive development program that includes upgrading prime

power. However, the potential cost savings, lower prime power requirements, and other

benefits of common design and hardware may make this an attractive option, particularly

if the U-2 and Global Hawk are both expected to play a significant role over the long

term.
30

APY-3

REPLACE

REMOVE

2-D Active

Electronically Scanned Array

(AESA)

Signal Processing

Ops & Control Upgrades

Datalink

Upgrades

Radar Technology Insertion Program (RTIP)

Technical Features:

25 Ft X 2 Ft

T/R module Design

Electronic AZ & EL

Increased Power (factor of ≅ 9)

Increased Bandwidth (factor of ≅ 9)

Advanced Signal Processing

Operational Improvements:

Faster MTI Revisit Rate (factor of 5)

Auto Track All MTI Targets

Improved MTI Classification

Simultaneous SAR and MTI

Increased SAR Resolution (factor of 10)

Reduced Life Cycle Costs

The new AESA has the major advantages of significantly increased radiated power

(about a factor of 10), higher efficiency, lower losses, lower noise figure, significantly

increased bandwidth and resultant range-resolution capability (about a factor of 10),

higher reliability, and simultaneous interleaved SAR and GMTI modes. A key benefit is

the very fast beam-switching rates possible with the AESA, which greatly increases the

flexibility of the radar to perform high data-rate tracking interleaved with other functions.

The enhanced system results in about a 1000 lb increase in sensor weight, and when

operated at maximum duty cycle requires a significant increase in prime electrical power

(a factor of 4-6) which is available from the current E-8A engines.
31

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32

The baseline RTIP program was approved by the Defense Acquisition Board (DAB) in

late 1999 for a program that delivers five production RTIP systems in CY 2012 for a total

cost of $2382M. The total cost includes $1,107M for EMD and $1,275M for production.

The program is based on developing two RTIP EMD prototype sensors  one scaled

lab sensor and one 24 ft flying prototype sensor that is to be installed and undergo

DT/OT flight test on the modified Joint STARS T-3 aircraft in CY05. The prototype

development plan includes fully developed software for all new base modes, including

surface SAR/GMTI and classified special and enhanced modes. Production is to include

the cost of complete modification of five current Joint STARS E-8A systems and

replacement (retrofit) of current APY-3 radars with a new RTIP active ESA radar and

complete software replacement.

The Task Force addressed the concern about the cost of the baseline program and not

meeting the 2010 schedule goal. The Task Force investigated an alternative

evolutionary approach that has two very cost-effective aspects:

1) Forward-Fit AESA Technology

The U.S. Congress has put additional funds in the past three DoD budgets to add

three additional Joint STARS production systems (P-14, P-15 and P-16). There

is every indication that this will continue and will include P-17, 18, and 19. If the

Air Force acts quickly, these new systems could be forward-fit with the new RTIP

AESA sensors rather than incurring the cost of retrofit, with the attendant benefit

that overall cost would be significantly reduced. It appears there is time to

accomplish this goal with P-16, which is currently scheduled for production

delivery in CY04 with the existing Joint STARS APY-3 sensor. Forward-fit of the

RTIP AESA into P-16 is estimated to save $70M. The Task Force feels that

19

RTIP Schedule Comparisons - DAB Approved Program vs.

Evolutionary Acquisition

CY00 CY01 CY02 CY03 CY04 CY05 CY06 CY07 CY08 CY09 CY010 CY011 CY012

CAIV / System Rqmts

S/W Development: Base, Special & Enhanced Full System Sensor (25)

Base

Sensor Development (2 Sensors)

Baseline DAB Approved Program

Flt Test

Production Retrofit

I&T on T3

DT/OT

 Total:

EMD: 1,107

Prod:1,275

2,382

 = Retrofit

 = Insertion

DAB Baseline

72 68 82 130 224 191 147 329 319 407 257 87 69

Evolutionary Acquisition Program (4 Forward Fit / 1 Retrofit - Total 19 Buy)

CAIV

Sensor Development

Block I

Port APY-3 Software

Block II

S/WDev : Special & Enhanced

I&T Flt Test

Prod Insertion

Block I

DT/OT

Block II

DT/OT

I&T on P-16

Total:

 919

 319

 1,238

0 0 0 0 0 0 0 148 197 386 257 87 69

Savings from DAB (Approx)

Savings:

 188

 956

 1,144

Prod:

EMD:

Evolutionary Acquisition Program (1 Forward Fit / 4 Retrofit - Total 16 Buy)

CAIV

Sensor Development

Block I

Port APY-3 Software

Block II

S/W Dev: Special & Enhanced

I&T Flt Test

Prod Insertion

Block I

DT/OT

Block II

DT/OT

I&T on P-16

Total:

 919

 723

 1,642

0 0 0 0 (38) (78) (69) 24 81 407 257 87 69

Savings from DAB (Approx.)

Savings:

 188

 552

 740

Prod:

EMD:
33

AESA technology has progressed to such a point that no compelling reason

exists for requiring a half-size lab sensor or an additional prototype sensor that

would never be upgraded to a production unit.

2) AESA Hardware InsertionEvolutionary Software Strategy

Additional time and risk savings are possible by using an evolutionary acquisition

strategy (Block I/Block II) for the software development, where the radar

hardware is upgraded to the new AESA radar hardware but is first operated with

the existing Joint STARS APY-3 software. Block I software modifications to

accomplish operation of the new hardware appear to be minor and would allow

DT/OT of the new hardware with the same functionality of the existing APY-3

software system, but with a significant increase in radiated power that would

allow integration times and dwells to be shortened. New software modes would

then be incorporated sequentially in Block II in modular steps for new capability

such as simultaneous SAR/GMTI vs. current single modes, multi-channel STAP

vs. the current 3-channel DPCA, ultra-high resolution SAR imagery, high range

resolution (HRR) for GMTI target recognition, simultaneous multi-beam modes,

high update GMTI track modes, and special classified modes that utilize the

significant increase in available radiated power. This would not only get AESA

production hardware into the inventory several years earlier but would further

reduce the program software development risk by allowing it to proceed in

parallel rather than in series with the hardware introduction.

It is estimated that the new evolutionary approach can deliver five modified systems with

new sensor hardware by FY07, with incremental software modifications completing

DT/OT by CY09 at a total cost savings of $740M and several years sooner than the

current base plan. If the new RTIP AESA hardware can be forward-fit into four systems

(P-16, 17, 18, 19), the total saving is estimated to be $1,144M over the base plan. This

saving is contingent on continuation of the current annual Congressional adds for

additional aircraft, but outfitting them with the new radar rather than the older design.

The same Block I/Block II evolutionary software approach would be utilized.

Early development, test, and evaluation of the new AESA hardware with proven software

allows the hardware change to be decoupled from the complicated task of developing

and integrating new system software. A separate, more graceful evolutionary insertion

of new modular software modes to substantially improve the end product can then be

tested in modular fashion on proven hardware. We feel the AESA hardware technology

has reached a sufficient level of maturity to forgo the lab sensor development with little

increased risk. In addition, based on the maturity seen in F-22 EMD and the JSF MIRFS

(multifunction integrated RF system) test beds, we feel that the EMD prototype unit can

be readily upgraded into a production system. Doing this in-line on a production E-8

rather than the T-3 test bed also represents a significant savings and reduces the

number of hardware sets to 5 rather than the currently planned 6.5. A number of extra

requirements are viewed as unneeded in the initial deliveries and can be postponed until

after the baseline advanced system modes are proven.
34

Based on the maturity of X-band AESA technology the Task Force feels the cost savings

are well worth the risk in a forward-fit hardware strategy. Quite simply, the strategy

avoids building new, but old-technology radars, which are already relatively expensive,

and then having to remove them for retrofit.

The evolutionary software strategy is also an important aspect of the recommended

plan. The software modes of these systems are increasingly very complex, and using a

sequenced development and test schedule controls cost and schedule risk.

SUMMARY OF ESTIMATED COST SAVINGS

EMD

 Eliminate Lab (Smaller) Sensor $100M

 Eliminate Extra Requirements $140M

PRODUCTION

 Avoid T-3 Install; Forward Fit EMD Sensor Directly to P-16 $ 70M

 Use refurbed EMD sensor for production vice Buy 1 Additional $120M

 Accelerate Time Span (eliminate 5 Years- gov’t and industry) $310M

TOTAL PROGRAM SAVINGS SUMMARY

 1 Forward fit/4 Retrofit Option Total $740M

 Additional Savings (4 Forward fit/1 Retrofit) $300M to $450M
35

IV. FINDINGS AND RECOMMENDATIONS

The findings of the Task Force are discussed throughout the report and are presented

here for completeness.

FINDINGS

• We concur that meeting the land-attack cruise-missile threat by 2010 is high priority

– JROC approved

• Good progress has been made in selected areas of advanced air defense

– Air Force has been the primary contributor beyond technology demonstrations

– Overall system engineering needs more attention

– Security rules should be reviewed to facilitate systems engineering

• Unanimous support for keeping JSTARS AESA on track

– Responsive to verified needs

– Important element in joint / allied warfare

– Baseline program costs are high - opportunities to restructure

• Global Hawk with an AESA

– Provides high-quality ground surveillance; first priority for additional ground surveillance capability

– Provides capability for selected air targets (surveillance and fire control)

– Enables closer standoff and penetration options

– The most attractive option to offload JSTARS and AWACS (the HDLD problem)

• Family-of-radars approach makes sense for airborne, X-band AESAs

– Fighters -- Global Hawk -- Business jets -- Large A/C

– Fighter radars dominate business picture - drive technology

– Family concept strongest in hardware; but significant in software also

– Contractors have motivation to develop product families to compete

– Do not see need for government to force to single family

– Requirements coordination across varied government customers required to realize successful families

• Unanimous opinion against “forced” contractor teaming on RTIP

– “Cream” from each unlikely when fighter AESA work dominates business picture

– Either contractor has broad skills to do job

– Impact of ACTD legacy (hardware/software) has been overcome by events

– Activity-to-progress ratio concerns

– Enough business for two teams

– Should not erode future competitive position in domestic and international market

• Technology needs for future combined function aircraft

– Lightweight, conformal arrays

– High efficiency modules

– Efficient prime power generation

•

– Not addressed in any detail

– Complex / multidimensional decision for the Air Force - not likely to occur soon

– Strong consensus not to delay recommended RTIP program to await platform decision

Platform Selection
36

The recommendations of the Task Force are discussed throughout the report and are

presented here for completeness.

RECOMMENDATIONS

• Proceed on RTIP program

– Restructure to forward-fit; EMD in-line; limited retrofit option

– Evolutionary upgrades in software modes to manage risks / costs and meet 2010 goal

• Support a “families-of-radar” airborne X-band AESA acquisition strategy

– Raytheon: F-15; F-18; JSF Demval; U-2

– Northrop Grumman: F-22; F-16; JSF Demval; RTIP

– Don’t “force” teaming

• Aggressively pursue a strategy leading to a multi-mission, X-band, AESA on Global

Hawk

– Give high priority to offloading demands on AWACS and JSTARS in situations other than

war

– Competitive procurement: two-team fly-off

– Phasing with RTIP and U-2 programs an important step in the family of radar concept

• The cruise missile defense systems engineering role needs to be better defined and

resources allocated

– Security review is an important part

 Future competitions

JSF -- Global Hawk – Army ACS –

NATAR – business jets – large A/C
A-1

Appendix A. TERMS OF REFERENCE AND TASK FORCE MEMBERS

TERMS OF REFERENCE:
A-2
A-3

TASK FORCE MEMBERSHIP:

Co-Chairs: Dr. David L. Briggs & Mr. Robert R. Everett

Members

Mr. John N. Entzminger

Dr. Theodore S. Gold

Dr. Matthew Ganz

Dr. Michael Gruber

Hon. Paul Kaminski

Hon. R. Noel Longuemare

Lt Gen George K. Muellner, USAF (Ret)

Dr. Dennis P. Murray

VADM James D. Williams, USN (Ret)

Executive Secretary

Dr. Glenn F. Lamartin

Executive Secretary Coordinators

Mr. Richard Burkholder

COL Thomas Cole

Military Assistant

LTC Scott McPheeters

Government Advisors

Dr. Emil R. Martinsek

Dr. John K. Smith

Dr. David A. Whelan

Meeting Schedule

29 Jun 00 Kickoff meeting

12-13 Jul 00

19-20 Jul 00

26-27 Jul 00

28 Jul 00 Brief-out

PRESENTATIONS TO TASK

FORCE:

Air Force (SAF/AQI, AQL)

Northrop-Grumman

Raytheon

JTAMDO

International Programs – NATO

AGS (OSD)

DARPA Special Projects Office

Defense Industrial Base (OSD)

Navy Special Programs

JLENS Program (Army)

MEADS Program (Army)

MTI Data Fusion Study (ASD/J2)

BMDO Radar Programs

CAIG JSTARS RTIP Report
B-1

Appendix B. AIR DEFENSE ASSESSMENT

In the brief time of this Task Force, we were able to do a cursory assessment of overall

advanced air defense activities. A summary of this assessment is presented in the

Table. The fighter area is moving along well with AESA technology insertion. AMRAAM

is a standout effort with substantial procurement in the near term. The area with

considerable shortfall is the BMC4I area. Also, beyond demos, there is little commitment

from the Navy and Army to preparing their missiles to permit airborne fire control

(ADSAM).

Advanced Air Defense Capabilities

(Table Entry is Unit Count)

Surveillance

 Airborne Fire Ctrl

 AWACS

 E-2

 JLENS

Fighters

 F-22

 F/A-18 E/F

 JSF

 F-15

Weapon Systems

 PAC-3 MSL/Radar

 MEADS

 S M

 AMRAAM

 CLAWS

BMC4I

 SIAP

 JTIDS Improvements

 JCTN

CEC

 E-2

 AEGIS

 CV

 Amphib

00 05 10 15

?

5

? Unfunded (must fund by 02 for 2010)

1 14

50 180 101

8 130 72

93 738

18

212 / 54 600 288

1 EMD 48

1794 3584

Must fund by 02 for 2010

14

?

?

?

24 50 5

16

7 5

11 24

?

25 12

Green: Significant Progress

Yellow: Moderate Progress

Red: Limited or no Progress
B-2

Several studies, including DSB studies, have addressed the Advanced Air

Defense/Cruise Missile problem in the recent past; see the references below∗. The

recent National Cruise Missile Defense Study report is due to be published soon. The

overall architecture of these defenses has generally been agreed upon and many

important “building blocks” have been demonstrated in ad hoc tests. Two potentially

important concerns in the national effort are 1) the need for more focused systems

engineering in bringing the family of systems/components together and 2) the

improvement in long-range non-cooperative combat ID techniques. The very promising

architectural concept of air-directed SAMs (ADSAM) can bring surface-based magazines

to bear against low altitude targets in over-the-horizon engagements to the kinematic

limit of the missiles. However, ADSAM requires strong systems engineering and

solution of the combat ID problem to reach full utilization.

Finally, the cruise missile defense area must continue to compete with other defense

needs for funding – in particular theater ballistic missile defense. Strong systems

engineering can be helpful here as well, since the air target and ballistic target must both

be accommodated by systems such as Aegis, Patriot, MEADS, and others.

 

∗

 Report of the 1994 Defense Science Board Summer Study Task Force on Cruise Missile

Defense; Final Report: January 1995; Dr. Theodore S. Gold and Mr. Walter E. Morrow,

Jr., Co-Chairs.

Report of the 1996 Defense Science Board Task Force on Land-Attack Cruise Missile

Defense; Final Report: May 1997; Dr. Theodore S. Gold, Chair.

National Cruise Missile Defense Study 2000 (NCMD Report to be published), sponsored

by OUSD(A&T)/S&TS (MW) in response to Congressional direction; Mr. Lee O. Upton,

Study Director.
B-3

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C-1

Appendix C. X-BAND AESA TECHNOLOGY

As pointed out in the body of this report, the maturation of AESA technology is enabling

a major leap forward in radar capabilities, including greater flexibility and a broader

range of missions that an AESA-based sensor can support. This appendix provides

additional background material on AESA technology, its evolution, and future direction,

as well as related areas of future research.

An overview of the differences between more traditional approaches to airborne radars

and AESAs is given first. The objective is to summarize the factors that make AESAs

such an attractive option for modern radars. The potential advantages offered by

AESAs are well understood by the radar community, but may not be familiar to those

outside that community. Recognition of this potential has motivated a great deal of

research and development on the central building element of an AESA, the T/R module.

Progress in both semiconductor device technology, as well as the integration and

packaging of this technology into modules sufficiently small and low-cost has made

AESAs a practical reality. This progress will be summarized in a chart showing T/R

module evolution and alternative array designs (so-called brick and tile designs).

The appendix concludes with a review of the findings of the study as well as directions

for future developments that contribute to expanding the capabilities of AESA-based

radar systems.
C-2

Digital signal output

Current (JSTARS) Advanced AESA

1- D ESA (Azimuth)

 - Mechanical Elevation Steering

Three Subapertures

 - Displaced Phase Center Antenna (DPCA)

 Processing

2- D Active ESA 

Multiple Subapertures

-Space-Time Adaptive Processing (STAP)

Solid State T/R Modules

Digital Beamformer

- ECCM

- Multiple Simultaneous Beams

- Mode Interleave

MTI Radar Antenna Architectures 

Ferrite Phase Shifters

Waveguide

Feed

Waveguide

Feed

Waveguide

Feed

Radiating Columns

A/D

A/D

A/D

Radiating Elements

T/R Modules

Power supplies

Receiver/Exciter

Waveform Generator

A/D Converter

Tube Transmitter

Waveform

Generator

High Power Tube Transmitter

Analog Beamformer

As an introduction to those not familiar with electronically steered array (ESA) antennas,

a brief overview of some basic features of these antennas in general, and AESAs in

particular is provided here.

The advantages of ESAs over mechanically steered antennas have long been

recognized. The most important of these advantages is the ability of ESAs to rapidly

(essentially instantaneously) steer the radar beam from any point within the field of view

to any other point. ESAs accomplish the rapid steering by inserting an electronic phase

shifter at each radiating element (or column of radiating elements in the case of

electronic steering in only one dimension). Beam steering is accomplished by subjecting

the signal at each radiating element to an additional phase shift such that the wavefront

resulting at the antenna face from the coherent addition of the output of each element

propagates in the desired beam direction. Similarly, on receive, the coherent addition of

the signal from the elements will cause the gain of the antenna to be maximized in the

direction selected by the phase shift at each element (beam pointing). Because the

electronic phase shifters can be switched very rapidly, with no mechanical inertia, beams

can be steered over even large angles in a small fraction of a pulse repetition interval

(PRI), i.e., from pulse to pulse. The task of computing the appropriate phase shift for

each element to achieve a particular beam steer direction is carried out by the beam

steer controller, an important subsystem of any ESA.
C-3

Many current ESAs rely on passive components, typically ferrite phase shifters, at each

controlled radiating element (or groups of elements) to achieve the necessary phase

shift function. Such arrays are generally referred to as passive ESAs, in contrast to

active ESAs (AESAs) which have active electronics, the T/R module, at each element

that provide the transmit and receive functions in addition to the phase shift required for

electronic steering. Although both passive and active ESAs share the benefit of rapid

beam steering over mechanically steered antennas, there are some significant additional

advantages that an AESA enjoys.

The chart highlights the basic differences between passive and active ESAs. For

purpose of discussion, a 1-D array, exemplified by the current JSTARS and ASARS-2

radars, will be assumed for the passive ESA. As shown in the diagram, passive ESAs

have a centralized, high power tube transmitter generating the required RF power. This

power is distributed to the radiating element via a power dividing network (corporate

feed) implemented in waveguide (“plumbing”) to handle the large peak power (typically

in the tens of kW range) of the tube transmitter. To generate this power, these

transmitters need high voltage power supplies in the tens of kilovolts. At each controlled

element (radiating column in this case) a ferrite phase shifter is inserted in the signal

path as described previously. On receive, the signal travels the reverse path, through

the phase shifter, possibly multiple corporate feeds (for multiple phase centers/antenna

beams), to receivers with low noise amplifier (LNA) front ends, and then to A/D

converters whose outputs are fed to the signal processor. Additional components in this

signal chain are required to switch the elements between transmit and receive (T/R

switches) and to provide isolation and protect against element mismatches (circulators).

Each of the passive components introduces loss in the system, thus contributing to a

degradation of radar sensitivity. In the case of the transmit path, RF power is lost in the

power distribution network (“plumbing”), phase shifters, circulators, and T/R switches.

On the return path these losses reduce the signal strength prior to the low noise

amplifier, thereby reducing the received signal to noise. Combined, these losses can

reduce the overall sensitivity on the order of 10 to 15 dB (a factor of 10 to 30).

By putting the final stage of transmit power generation, as well as the receive amplifier, at

the radiating element, these losses can be greatly reduced. To accomplish this reduction,

the T/R modules, containing the phase shifter, transmit power amplifier, T/R switch

(possibly including a circulator), and the LNA/receiver are located as close to the radiating

element as possible, with the radiating element in some cases being made an integral part

of the module itself. Although signal distribution and combining networks are still required

“behind” the modules, their losses are no longer important. In the transmit path these

losses occur prior to the final transmit power amplifier and thus do not affect the final

power output. In the receive path, the losses associated with the combining networks

(analog beamformer) occur after the LNA and receiver preamplifier and hence do not

reduce the incoming signal strength prior to amplification. The net result is that while not

all losses can be eliminated (e.g., circulator losses) a reduction in overall losses in the

order of a factor of 10 or greater is feasible in AESAs compared with passive ESAs.

Because losses in the RF circuitry behind the T/R module are less important, lower cost

and lighter weight (as well as less bulky) distribution/combining techniques, essentially

printed circuits, can be used instead of waveguide components. Similarly, the phase

shifter, which is part of the T/R module, is also placed before the power amplifier and after

the receive amplifier. This allows it to be implemented using solid state integrated circuitry
C-4

which, among other benefits compared to ferrite phase shifters, can be switched much

more rapidly and with essentially no power.

Just as the RF power generation is distributed over the array, the regulated DC power

supplies are similarly distributed, with one supply typically feeding multiple T/R modules.

Unlike high power tube transmitters, voltages for T/R modules are low (~10 V) and

distributing the power generation over multiple power supplies close to the T/R modules

they supply is necessary to avoid high ohmic losses and problems with supply regulation.

However, these supplies can be efficiently integrated into the antenna itself to simplify

power interfaces.

A second, major advantage of an AESA over a passive ESA or a mechanical array is the

mean time between critical failures (MTBCF). Since the power supplies, final power

amplification and input receive amplification, are distributed, MTBCF is significantly higher,

10-100 times, than that of a passive ESA or mechanical array. This results in higher

system readiness and significant savings in terms of life cycle cost of a weapon system,

especially a fighter. For fighter and UAV applications, these large MTBCF may ultimately

mean little or no radar array maintenance is required for the life of the platform.
C-5

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C-6

The potential advantages of AESAs have long been recognized by the radar community.

The major challenge has been to develop the technology and manufacturing capability to

achieve the size, weight, power, and cost necessary to make AESAs affordable and

cost-effective alternatives to traditional approaches to airborne radar (such as

mechanically steered antennas initially, and more recently, passive 1-D ESAs). A key

pacing element in this development has been the T/R module. Developments in this

area have focused on (a) semiconductor chip technology to achieve low noise figure

receive amplifiers (LNAs) and high power transmit amplifiers (PAs) having high poweradded efficiency (a crucial parameter in defining prime power and cooling requirements),

and (b) integrating the various component chips (including digital logic) into a module

that can be manufactured using a high degree of automation for both assembly and test.

Although it took considerable time and investment, this technology has now matured to

the point where AESAs have become the approach of choice for the high performance,

multifunction radar sensors essential to continued dominance in modern weapon and

ISR platforms.

The performance advantages offered by AESAs have been particularly important for

modern fighter aircraft, and it is the application to fighter radars that has spurred on the

rapid progress made in recent years. An illustration of this progress in T/R technology is

the reduction in T/R module size over the past 40 years as shown in the chart. This

reduction has allowed the development of compact, high power AESAs suitable for

integration into the nose of a fighter. This is illustrated by the picture of the F-22 AESA

shown above. Additional reduction in T/R module size, combined with even greater

SOLID STATE PHASED ARRAY ANTENNAS

Key to Modularity

T/R Modules

1960 - present F-22 Aperture

1980s

JSF Dem-Val Aperture

1990s

• Multifunction Arrays

• AMTI, GMTI, SAR

• Search, Track, Weapon Support

• Increased Performance, Lower Cost

• Highly Reliable, Low Weight

2000s
C-7

levels of integration, has resulted in further reduction in the depth (and weight) of the

AESA as shown by a dem-val version of the JSF radar. Reduction in the T/R module

size requirements can be leveraged in the so-called tile approach, where the various

functions required for the AESA (power distribution, RF distribution, timing and control)

are implemented in a multiayer “circuit board” which also contains layers for the T/R

“modules” and antenna radiators. An example of such a highly integrated design

concept for future AESAs is shown in the figure.
C-8

The trend in the reduction in both weight and cost resulting from advances in T/R

module technology as well as higher levels of integration in the array itself are

illustrated in this chart which appeared in a recent issue of Aviation Week and

Space Technology∗. The chart shows the reduction in both weight and cost of

representative arrays over the past five years, as well as an extrapolation into the

near future where the large procurement expected for the JSF radar is expected

to provide the fuel for further development leading to additional cost reductions.

The examples in the chart show the significant reduction in weight and cost (by

almost a factor of 5) over the past half-decade. As the technology matures, this

trend will level off in the future. However, it has propelled T/R modules in

particular, and AESAs in general to a position of dominance in future high-end

airborne radar application  both for nose-mounted fighter radars and sidelooking ISR platform radars (as well as others such as ground-and ship-based

systems where AESAs provide comparable advantages over conventional

radars).

 

∗ David A. Fulghum, “New Radar Design Uses Unique Building Blocks,” Aviation Week and

Space Technology, 11 September 2000

Aggressive Array Weight and Cost

Reduction Demonstrated Since 1995
C-9

As mentioned previously, AESAs are well suited for a family-of-radars approach, which

allows leveraging the gains already achieved for fighter radars to the next generation of

side-looking radars for airborne ISR platforms, both manned and unmanned. Clearly the

optimum level at which commonality is imposed will require careful assessment of tradeoffs between the benefits (e.g., cost and schedule savings) and compromises (e.g., in

performance) compared to highly customized designs.
C-10

This chart summarizes, in broad terms, the technology findings of the Task Force. It is

clear that T/R module technology will be driven by requirements imposed by fighter

radars  the anticipated market for these radars far outweighs that for side-looking ISR

radars. It is therefore imperative that ISR needs draw upon the family of modules that

have been and will be developed for fighter radars. However, it may prove to be

advantageous to customize modules by modifying (direct replacement) chips within the

module to more efficiently match differences in power requirements between the two

types of applications.

AESA architectures are inherently modular and provide a “natural” basis for a family-ofradars approach. It is therefore not surprising that both Raytheon and Northrop

Grumman, the leading sensor houses for airborne radars, have adopted this approach to

meeting diverse radar needs. The way in which members within this family differ may

vary with the specifics of the approach. Within the class of fighter radars the degree of

commonality is generally quite high. The level of commonality between fighter radars

and ISR (side-looking) radars will undoubtedly have to be less. For example it is unlikely

that subarrays (a system-level modular AESA building block discussed earlier) will be

the same  fighter radars generally are circular apertures, whereas side-looking radars

typically are rectangular with high length-to-width ratios (longer antennas are desirable

Technology Findings

• Future fighters radars will drive T/R module technology

– ISR modules must be part of this family of modules with possibly

small changes to match power requirements

• Family-of-radar/product line sensor concept is being adopted

within each sensor house

– Commonality at a subarray level with fighters appears unlikely due to

constraints on fighter integration

• Open systems architecture must be applied to software

– A workable standard that allows upgrades to RF hardware as well as

processors needs to be developed

• RF hardware technology research in lightweight apertures,

conformal array, and receiver/exciters will allow a large decrease

in size, weight, power, and cost.

• Current UAV platforms are prime power limited

– Efficient prime power generation technology for high altitude

platforms critical to fully exploit AESA potential
C-11

to achieve good GMTI performance). However, at higher levels, e.g. after the subarrays,

a high degree of commonality should be possible. In particular, there is considerable

functional commonality, i.e., both fighters and ISR platforms perform surveillance and

target tracking. Consequently, a modular, open systems architecture for software is a

key underpinning of the family-of-radars approach. In this context it is also considered

essential that a workable standard be developed that supports upgrading the family-ofradars as improvements in RF and processor hardware are realized through technology

growth.

Such technology growth will benefit all AESA applications, but is of special interest for

platforms such as Global Hawk where size, weight, power, and cost play a particularly

important role in enhancing the operational utility of these platforms, making them more

capable and affordable. Research in lightweight apertures, conformal arrays, and

improved receiver/exciters will help to take full advantage of available platform payload

capacity and offer new opportunities for radar and other sensors (e.g., SIGINT) to be

integrated with the platform.

The greater overall power efficiency offered by AESAs is an important factor in

increasing the performance of airborne radars. However, in platforms such as the

Global Hawk UAV, the extent of the performance improvements that can be realized is

limited by the prime power available for the radar. While incremental improvements in

T/R module efficiency and in the power efficiency of other components can alleviate the

problem somewhat, to achieve a major increase in UAV operational capabilities in

general, and radar sensitivity in particular, will require a significant increase in the

available prime power. In the case of Global Hawk a two to threefold increase will be

necessary to fully exploit the AESA potential. To reach this goal without a major impact

on the endurance and altitude of Global Hawk (or requiring a major platform redesign),

efficient generation of prime power at high altitude is essential. This should be possible

by applying current power generation technology to the Global Hawk vehicle, with a

small compromise in endurance. UAVs will benefit from power generation efficiencies in

the future with the development of the internal engine starter/generator, which should

have little impact on the engine efficiencies but increase power generation by about

fivefold.
D-1

Appendix D. LIST OF ACRONYMS

A/D Analog to Digital (Converter)

ACS Aerial Common Sensor

ACTD Advanced Concepts Technology Demonstration

ADSAM Air Directed Surface-to-Air Missile

AESA Active Electronically Steered Array

AGS Alliance Ground Surveillance

AIP ASARS Improvement Program

AMRAAM Advanced Medium-Range Air-to-Air Missile

AMSTE Affordable Moving Surface Target Engagement

ASARS Advanced Synthetic Aperture Radar System

ASTOR Airborne Stand-Off Radar (United Kingdom Program)

ATACMS Army Tactical Missile System

AWACS Airborne Warning and Control System

BMDO Ballistic Missile Defense Organization

CAIG Cost Analysis Improvement Group

CAIV Cost as an Independent Variable

CLAWS Close Combat Light Armor Weapon System

CNAD Conference of National Armaments Directors (NATO)

DAB Defense Acquisition Board

DARPA Defense Advanced Research Projects Agency

DoD Department of Defense

DPCA Displaced Phase Center Antenna

DSB Defense Science Board

DT/OT Developmental Test/Operational Test

ECCM Electronic Counter-Countermeasures

EMD Engineering and Manufacturing Development

EO/IR Electro-Optic/Infrared

ESA Electronically Steered Array

ESM Electronic Support Measures

GBR Ground-Based Radar (X-band radar for National Missile Defense)

GHAWK Global Hawk UAV

GMTI Ground Moving Target Indicator
D-2

GRCA Ground Reference Coverage Area

HDLD High Demand Low Density

HPD High-Power Discrimination (Radar)

HRR High Range Resolution

ISR Intelligence, Surveillance, and Reconnaissance

JCTN Joint Composite Tracking Network

JLENS Joint Land Attack Cruise Missile Defense Elevated Netted Sensor

JSF Joint Strike Fighter

JSTARS Joint Surveillance Target Attack Radar System

JTAMDO Joint Theater Air and Missile Defense Organization

JTIDS Joint Tactical Information Distribution System

LNA Low Noise Amplifier

MDV Minimum Detectable Velocity

MEADS Medium Extended Air Defense System

MFR Multi-Function Radar

MIRFS Multifunctional Integrated RF System

MMIC Monolithic Microwave Integrated Circuit

MTBFC Mean Time Between Critical Failures

NATAR NATO Transatlantic Advanced Radar

NATO North Atlantic Treaty Organization

PAC-3 Patriot Advanced Capability Level-3

RF Radio Frequency

RTIP Radar Technology Improvement Program

SAR Synthetic Aperture Radar

SIAP Single Integrated Air Picture

SIGINT Signals Intelligence

SM Standard Missile

SOSTAR Stand-Off Surveillance Targeting and Acquisition Radar

STAP Space-Time Adaptive Processing

T/R Transmit/Receive (Module)

THAAD Theater High Altitude Area Defense

UAE United Arab Emirates

UAV Unmanned Aerial Vehicle