DTIC ADA515506: Radar Versus Stealth: Passive Radar and the Future of U.S. Military Power

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by  Defense Technical Information Center

Radar versus Stealth
Passive Radar and the Future of
U.S. Military Power
F
aced with the prospect of aerial
By Ar enD G. Westr A
stealth proliferation, states in
the 21st century are looking for
antistealth defense options. One
such alternative, passive radar, appears a cost-
effective counter to stealth. Passive radar is a
receive-only system that uses transmitters of
opportunity.1 Integrating a system of netted
receivers, passive radar can detect, track, and
target piloted and unpiloted stealth systems
and provide cuing for antiair weapons
systems. A passive radar system emits no
radio energy and can be well camouflaged in
both urban and rural landscapes. The threat
system produces no indications on friendly
radar warning receivers and is difficult to
locate and target. Faced with a passive radar
threat, the United States may find itself unable
to achieve air superiority at an acceptable cost.
As this article shows, ongoing advances
in passive radar will deny traditional means
to defeat enemy air defenses, make air supe-
riority difficult to achieve against a passive
radar opponent, and require changes in
thinking to maintain U.S. power projection
capability. In developing this central idea,
this article describes the history of the battle
between aircraft and radar, the rise of stealth
and counterstealth, and the ongoing surge in
passive radar and how it relates to advances
in signal processing and sensor fusion. Addi-
tionally, this article assesses the passive radar
threat to stealth, posits implications for future
U.S. military power, and recommends a U.S.
course of action regarding passive radar.
Aircraft versus Radar
“The defensive form of warfare is
intrinsically stronger than the offensive”—so
argued Carl von Clausewitz in On War.2 The
man) static warfare of the late 19th century and the
Way
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136 JFQ / issue 55, 4th quarter 2009 ndupress.ndu.edu
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WESTRA
Great War of 1914–1918 appeared to validate transmitter and receiver via a shared antenna, a always get through.” Indeed, stealth aircraft
this idea. In 1921, however, Giulio Douhet configuration known as monostatic, thus creat- have maintained the overwhelming advantage
asserted that the airplane changed warfare ing the conventional radar configuration most in recent conflicts, including Operation Allied
“by magnifying the advantages of the offense commonly used thereafter. Force and the invasion of Iraq in 2003.
and at the same time minimizing, if not nul- Historically, radar has been the corner- Despite the overall success of the U.S.
lifying, the advantages of the defensive.”3 stone of air defense. For example, during the stealth program, in 1999 an F–117 was shot
Douhet did not envision the many sur- Vietnam War, North Vietnamese air defense down in the Balkans by a Serbian SAM
face-to-air threats that would evolve over the radars targeted U.S. aircraft, which, in turn, battery.15 Although some considered the
decades after his work was published. Neither countered with jamming and antiradiation downing an anomaly, the incident created
did airpower critics. As Sir Stanley Baldwin missiles. Due to the success of North Viet- much controversy. While the Air Force
informed the British parliament in 1932, “I namese air defenses, the United States was assessed tactical lessons learned, others saw
think it is well also for the man in the street only able to establish temporary air superior- evidence that stealth could be defeated.16 The
to realize that there is no power on earth that ity over local areas of North Vietnam. Over incident illustrated what stealth designers
can protect him from being bombed, what- the course of the war, the North Vietnamese already knew: stealth technology does not
ever people may tell him. The bomber will shot down 190 U.S. aircraft using 1950s-era make an aircraft invisible. As a submariner
always get through.”4 Russian surface-to-air missiles (SAMs).10 once aptly noted, “Stealth is a zero-sum game.
Yet a few decades earlier in 1904,
German engineer Christian Hülsmeyer had
the overwhelming offensive power of the airplane was largely
patented the telemobilskop, an early form of
mitigated by the deployment of radar and modern air defenses
radar. But it was not until 1935 that radar first
showed significant operational promise. In
the now famous Daventry experiment, Sir A third paradigm shift began in the In a given encounter, one platform has it
Robert Watson-Watt used radar to detect a 1970s in the “Skunk Works” of Lockheed and the other does not. The tactical advan-
British Heyford bomber at a range of 8 miles.5 Martin, where stealth pioneers first created tage accrued by being able to detect, close,
Notably, the Daventry experiment tested a the F–117 “stealth fighter” (more bomber than and attack from a covert stance completely
passive radar system using the BBC Empire fighter in usage).11 Made operational in 1983, dominates all other factors in any encounter
broadcast as a transmitter of opportunity.6 the F–117 saw combat in Panama in 1989 and algorithm.”17 In Serbia in 1999, a SAM battery
Watson-Watt went on to develop the British again in the Gulf War in 1990.12 During the commander attacked from a covert stance and
Chain Home radar that played a critical role Gulf War, the F–117 was employed against won the tactical advantage. It was a missile
in defeating the German Luftwaffe during the Iraq’s most heavily defended targets. In spite shot heard around the stealth world.18
Battle of Britain in 1940.7 of Iraq’s robust air defenses, not a single F–117
World War II served as catalyst for a was lost or damaged during the conflict.13 By The Future of Stealth
second paradigm shift. The overwhelming comparison, 32 nonstealth aircraft were lost If anything, the downing of an F–117
offensive power of the airplane was largely to antiaircraft artillery (AAA) and SAMs.14 If over Serbia only highlighted to the United
mitigated by the deployment of radar and Baldwin had witnessed the Gulf War, he might States the importance of stealth. Increasingly,
modern air defenses. Airpower did not prove have concluded, “The stealth bomber will the U.S. military has made stealth one of its
Figure 1. Bistatic Geometry
an all-powerful offensive weapon that could
not be countered, and the bomber did not
Figure 1. Bistatic Geometry
always get through. Air defenses of both the
Axis and Allied opponents proved complex
and resilient, and combatants obtained air TARGET
superiority only locally and for limited dura-
tions through the costly reduction of enemy
air defenses. This paradigm held firm through
Rtx ß Rrx
World War II and for the duration of the
Cold War. For the time being, it seemed that
Clausewitz had caught up with the airplane.
Despite Watson-Watt’s breakthrough at
L
Daventry, the experiment highlighted passive
radar’s difficulties, including intermittent signal TRANSMITTER RECEIVER
strength and, at the time, irresolvable locating
and tracking ambiguities due to the passive
Note: L = distance between transmitter and target ("bistatic baseline");
radar geometry.8 Passive radar is bistatic, Rtx = transmitter range to target; Rrx = receiver range to target;
ß = bistatic angle.
meaning the receiver is located at a distance
from the transmitter.9 Bistatic radar geometry Source: C.J. Baker and H.D. Griffiths, Bistatic and Multistatic Sensors for Homeland Security (London:
University College, 2005), 4, available at <http://nato-asi.org/sensors2005/papers/baker.pdf>.
is shown in figure 1. In 1936, scientists solved
the difficulty of geometry by collocating the
ndupress.ndu.edu issue 55, 4th quarter 2009 / JFQ 137
FEATURES | Passive Radar and the Future of U.S. Military Power
highest priorities, both in terms of new acqui- signature is defined as all the observables on a radars where the receiver is collocated with
sitions and the retrofit of older aircraft. In stealth platform that require external illumina- the transmitter and is less effective against
short, stealth is the centerpiece of the U.S. air tion. . . . The active signature reduction methods bistatic radar geometry.27 Radar-absorbent
superiority strategy. are commonly called low probability of intercept material augments fuselage shaping by
As stealth grows ubiquitous, nonstealth (LPI). . . . Passive signature reduction techniques absorbing radar energy and reducing the
systems will become rare. Stealth principles are are often called low observables (LO).23 strength of the radar echo.28 Future innova-
evident in nearly every newly developed mili- tions may allow stealth aircraft to actively
tary aircraft, ship, and ground combat system. Stealth designers attempt to balance cancel radar echo by retransmitting radar
Nations devote large proportions of their signature techniques.24 For example, efforts energy and/or by ionizing boundary layer air
military budgets to stealth research and devel- to make an aircraft less visible at 5 miles are around the fuselage.29
opment. And with the Air Force having retired somewhat superfluous if it can be acquired by
the F–117 in 2008, the United States now has an infrared (IR) sensor at 20. LPI designers Counters to Stealth
a shortage of operational stealth aircraft.19 focus most of their efforts on reducing the Before discussing passive radar, several
Current U.S. stealth aircraft inventory consists emissions produced by the aircraft’s radar other radar and sensor systems are worth
of 20 B–2 bombers and 187 F–22s, with the and IR sensors.25 In designing LO, the main mentioning in terms of counterstealth capa-
Joint Strike Fighter projected to become opera- concern is reducing reflection in the radar bility. One of the most significant counters
tional in 2012.20 Planned U.S. procurement spectrum, also known as the radar cross to stealth, namely conventional very high
for the Joint Strike Fighter is 2,456 aircraft section (RCS). frequency (VHF) and ultra high frequency
delivered over a 28-year period.21 Meanwhile, (UHF) radar, has been around since World
Russia, India, China, Japan, and other coun- stealth is achieved by a broad War II and is still in use today for long-range
tries are attempting to enter the stealth aircraft collection of techniques that air surveillance. Most LO techniques are
market.22 In short, stealth is relevant, in much designed to defeat acquisition and fire control
render a platform difficult to
demand, and continuously evolving. radar in the X band, which uses centimeter
locate and attack
wavelength. VHF- and UHF-band radar,
Stealth Techniques however, uses decimeter- to meter-long
Stealth is achieved by a broad collection Designers reduce RCS primarily wavelength. In general, the RCS of an aircraft
of techniques that render a platform difficult through fuselage shaping and radar-absorbent increases as wavelength of the illuminating
to locate and attack. It requires reducing air- material. Fuselage shaping, the more impor- radar increases.30 Furthermore, when the
craft signature, generally categorized as either tant of the two methods, reflects radar energy radar wavelength is in the same order of mag-
active or passive: away from the direction of the emitter.26 nitude as the aircraft or parts of it, the radar
Figure 2 depicts a stealth aircraft RCS versus waves and the aircraft resonate, which signifi-
Active signature is defined as all the observable that of a conventional aircraft. Fuselage cantly increases the RCS of the aircraft.31 It
emissions from a stealth platform. . . . Passive shaping works primarily against conventional is the physics of longer wavelength and reso-
Figure 2. Conventional and Stealth Aircraft Radar Cross Section Signature
dBsm CONVENTIONAL AIRCRAFT NOTIONAL STEALTH AIRCRAFT dB
35 40
30 30
25 20
20 10
15 0
10 -10
5
Note: dBsm = decibels per square meter; dB = decibels
Source: David Lynch, Introduction to RF Stealth (Raleigh, NC: SciTech, 2004), 6.
138 JFQ / issue 55, 4th quarter 2009 ndupress.ndu.edu
WESTRA
nance that enables VHF and UHF radar to MMW antiair missile seekers, and other off-the-shelf technology makes them attrac-
detect stealth aircraft. Poor resolution in angle countries are following suit.37 tive for nonpeer countries as well.
and range, however, has historically prevented While the aforementioned technologies Passive radars use transmitters of
these radars from providing accurate target- offer important capabilities, they possess opportunity. Potential waveforms include FM
ing and fire control.32 limitations that restrict their effectiveness and AM radio, television, digital audio/video
Since the Gulf War, the Russian defense for air defense. Conventional radar is vulner- broadcast, and cellular phone networks.38
radar industry has put considerable effort into able to detection and attack by electronic Today, passive radar is often configured as
digitizing its VHF and UHF radar systems warfare and air-delivered weapons; listening a “multistatic” system using three or more
to improve counterstealth capability. Russia’s systems do not provide tracking information; transmitters and receivers.
older model radars now have improved reso- and IR/EO/MMW is limited in surveillance Passive radar locates and tracks targets
lution and signal processing, and newly devel- capabilities. through a combination of methods, greatly
oped models, such as the Nebo surface vehicle In contrast, passive radar is covert, all simplified here for the sake of discussion.
unit, which is a VHF adaptive electronically weather, and capable of medium- to long- First, the radar measures the time difference
steered array radar, likely present significant range surveillance, and shows strong potential of arrival between the direct signal from the
counterstealth capability.33 in detecting, tracking, and targeting stealth transmitter and the reflected signal from the
Other recently developed conventional aircraft. It is thus emerging as a solid competi- target to determine the bistatic range. Bistatic
radars likely to have counterstealth capabil- tor in the counterstealth game. range, expressed as an ellipse, is shown in
ity include Lockheed Martin’s theater high-
altitude area defense radar and the Israeli
a new paradigm is emerging, enabled by advances in
Green Pine radar (recently sold to India),
networked computing and passive radar technology
systems with both long range and high
resolution in the UHF L-band.34 The Signal
Multi-beam Acquisition Radar for Tracking Passive Radar figure 3. The radar uses the intersection of the
(L) naval radar manufactured by Thales is A new paradigm is emerging, enabled by receiver-to-target bearing and the bistatic range
yet another system with reputed counter- advances in networked computing and passive ellipse to estimate approximate target location.
stealth capability.35 radar technology. Because of their potential to In a multistatic system, the radar refines target
Passive listening systems, such as elec- counter stealth-based airpower advantage, the location based on intersecting bistatic range
tronic support measures (ESM) and direc- use of these technologies by peer competitors ellipses. The radar further measures Doppler
tion finding (DF), attempt to detect stealth is highly likely. That these systems are both shift—wavelength compression or expansion
aircraft radar, radio, and data link emissions low cost and, in part, based on commercial- caused by relative motion—to determine target
and pass this information to surveillance
radars. LPI techniques of stealth are designed Figure 3. Bistatic Range
Figure 3. Bistatic Range
to reduce or deny ESM and DF, but systems
such as the Russian Kolchuga remain formi-
dable threats that are likely being updated
with digital processing.36 TRANSMITTER
Another counter to stealth is IR/electro- 0
optical (EO) systems, which include IR search Rtx TARGET
and track and high magnification optics. Such
systems, however, are limited in the ability
to scan large volumes of airspace and usually
must be cued by other sensors. In addition,
L Rrx
most of this spectrum is degraded by clouds,
low illumination, and low visibility. Stealth
aircraft counter IR/EO through heat signature
management, stealthy flight profiles, and LO
paint schemes. Constant range 0
Growing in potential as a counterstealth ellipse RECEIVER
technology is millimeter wave (MMW)
imaging, which uses the radiometric signa-
ture naturally emitted by all objects. MMW
penetrates clouds and low visibility. The wave- Note: Rtx = transmitter range to target; Rrx = receiver range to target;
L = distance between transmitter and receiver. Bistatic range, expressed as Rtx + Rrx – L,
form can also be transmitted by radar, which
remains constant at all points on the ellipse.
then receives and processes the return echo.
The A–64 Apache Longbow/Hellfire system Source: NationMaster Encyclopedia, “Bistatic Range,” available at <http://www.nationmaster.com/
is an example of operational MMW radar. encyclopedia/Image:BistaticRange.png>.
The Russian defense industry has developed
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FEATURES | Passive Radar and the Future of U.S. Military Power
heading and speed. The radar tracks the target are frequency, bandwidth, and the presence radar. Digital audio broadcast, while a useable
by performing regular updates. of continuous wave, which provides Doppler waveform, emits at low power, offering only a
Advanced signal processing allows shift for measurement of velocity.44 Also short detection range of 36 km.48 Use of more
passive radar to integrate data from multiple important is whether illuminators transmit than one waveform is possible, with existing
receivers, cancel signal interference, differenti- continuously or with significant interruptions systems touting accurate three-dimensional
ate real targets from ghost returns and clutter, (for example, daytime only). surveillance capabilities across multiple wave-
and establish a target track. Although such pro- Several waveforms in the HF, VHF, and forms, to include FM radio and analogue and
cessing requires significant computing power, UHF bands have shown potential for use in digital television.
most passive radar systems operate on com- passive radar and also exhibit counterstealth Most important to this discussion, all of
mercial DOS-based computing technology. properties. In the VHF band, FM radio is the aforementioned waveforms fall between
The recent advances of passive radar broadcast at high relative power and has mul- 3 and 450 megahertz. Based on their decime-
arise from a confluence of digital processing tiple transmitters available in moderately to ter- to meter-wavelengths, these waveforms
technology, cheap, sophisticated hardware, heavily populated regions. Analog television inherently increase RCS and also interact with
and the demand for enhanced surveil- (VHF band) also provides useful illumina- an aircraft to create resonance. RCS induced
lance.39 Moore’s law describes the doubling tion, as does digital audio broadcast, which is by resonance is largely independent of fuse-
of computer processing speed every 18 growing in usage worldwide. High-definition lage shape. In short, radar in this spectrum is
months. Meanwhile, designers have made (HD) television is spreading globally as well inherently counterstealth.
significant advancements in correspond- and offers a wideband, high-power waveform While passive radar can perform detect-
ing radar software. What was once thought in the low UHF band. In the HF band, Digital ing, locating, and tracking functions, it may
impossible—that is, integrating signals from Radio Mondiale (DRM), a digital form of also be able to perform target identification
multiple receivers and detecting tiny echoes shortwave AM radio, also has passive radar (ID). Under development are methods to
in high-clutter radar environments—has now potential. conduct target imaging using multistatic
become feasible.40 These waveforms offer differing levels UHF-band Inverse Synthetic Aperture
As a result of this confluence of of utility. Analog television and FM radio Radar.49 Additionally, existing passive ID
technology, several systems are now either both offer strong illumination and medium measures, such as DF/ESM, will likely
available off the shelf or are in development. detection ranges—FM out to roughly 120 augment passive radar.
Such systems include Lockheed Martin’s kilometers (km).45 Analog television has a If successful at creating a target track
“Silent Sentry,”41 Roke Manor Research’s strong signal but suffers from interference, and ID, passive radar could provide cueing for
CELLDAR,42 Thales-Raytheon’s Homeland while FM is marked by interruptions, such as surface-to-air and airborne weapons systems
Alerter,43 and others, including French, pauses during human speech.46 HD television in order to enable acquisition. Weapons system
Swedish, Chinese, and Russian systems. provides an uninterrupted signal with a detec- cueing requires communications infrastruc-
Certain commercial waveforms are tion range of 120 km.47 DRM potentially offers ture; for a covert system, this means a local
more suitable for passive radar illumination over-the-horizon detection ranges; however, area network for ground-based weapons and
than others. The most important parameters low resolution limits its use to early warning an LPI data link for airborne platforms. For
F–117A Nighthawk stealth fighter
while passive radar can
perform detecting, locating,
and tracking functions, it may
also be able to perform target
identification
SAMs with a command guidance mode, the
passive radar could provide midcourse guid-
ance via data link. In keeping with the passive
radar system, a passive missile seeker—IR, EO,
MMW, or perhaps multisensor—would likely
be used for end-game guidance in order to
complete the kill chain.
way) Threat employment
Duna A future adversary will look increasingly
Andy to counter the U.S. stealth advantage with
Air Force ( pora sisni vceo nrajudnarc,t eioitnh ewri tahs aa csttiavned s-uarlvoeniell saynsctee m
U.S. radars. Passive radar is relatively cheap, and
140 JFQ / issue 55, 4th quarter 2009 ndupress.ndu.edu
WESTRA
its covert stance lends itself to a strategy of Electronic warfare (EW) offers the Building new generations of stealth
striking from concealment. Moreover, our potential to temporarily neutralize passive aircraft may be feasible, but efforts to
most likely future opponent—an authoritar- radar. Standoff noise jamming would have improve stealth will eventually reach a point
ian state—already possesses tight control over an effect, but because the location of the of diminishing returns. Advantages will
its commercial media, a situation that requires receivers is unknown, the jammer would grow more difficult and expensive to achieve
a relatively small step to optimize broadcast- need to emit across a wide sector, unavoid- as counterstealth technologies concurrently
ing parameters for passive radar use. ably reducing jamming signal density.51 grow more advanced.
This same adversary will build a passive
multistatic receiver network in the VHF and North Vietnamese surface-to-air missile
crew in front of SA–2 launcher
UHF bands, blending the system into the
vertical buildup of urban terrain.50 In remote
areas not served by media broadcast, the
adversary may disperse a network of inex-
pensive throw-away transmitters to function
as the surveillance area illuminators. He will
integrate passive radar and other sensors for
rapid, efficient command and control. It is
likely that such an adversary will make efforts
to develop or acquire passive SAMs with low
observable launch signatures and procure and
deploy high- and mid-altitude unmanned
aerial vehicles—“missile trucks”—to deny
flight at those altitudes.
Countering Passive Radar
Countering passive radar will prove
difficult. What are the signs that an opponent
iosf uthsien tgh preaasts imvea rya pdraorv? iFdoe raenh aidneda k onf ogwenleedragle Air Force
capabilities. Are friendly air forces losing U.S.
aircraft to ground fire with little or no threat
warning indications? With no radio frequency basic stealth techniques will be less effective than they once
electronic intelligence available, locating the
were against passive radar systems that benefit from bistatic
passive radar receivers will be challenging.
geometry and the use of counterstealth waveforms
Intelligence will face a difficult task of using
indirect methods—human intelligence,
ground surveillance, computer network Moreover, deception jamming may be of Implications
operations, and nodal analysis—to collect on limited use against passive radar, also due to Passive radar has many implications for
sparse information. the unknown receiver location.52 Other types future U.S. military power. Stealth will con-
If the command and control nodes and of jamming, however, may prove highly effec- tinue to be a critical feature of tactical military
receivers cannot be found, targeting planners tive. Overall, the lack of known threat loca- aircraft, particularly as a defense against pres-
could focus on destroying suspected trans- tion bolsters the argument for a robust EW ently fielded weapons systems. As is evident
mitters—for example, FM radio, television, capability that is integral to friendly multirole in the continued proliferation of conventional
and HD television networks. Depending on aircraft. Advocacy for or against a dedicated radar SAMs and AAA, these threats are not
their location and the potential for collateral EW platform, however, is beyond the scope of going away any time soon.
damage, however, destroying these targets this article. Stealth airframes require long design
may result in undesirable strategic conse- Other means of countering passive and procurement processes, whereas avion-
quences, particularly in urban areas. radar include special operations and computer ics and software are more readily modified.
At the tactical level, friendly forces could network attack. In the end, targeting passive This phenomenon is driving a philosophy
employ reactive defenses against SAM launch radar systems may fall in the “too hard” cat- in tactical aircraft design that basic stealth
and fly-out and conduct immediate counter- egory for limited warfare. Missile systems— techniques are the critical solid foundation
attack of associated threat systems through mobile SAMs, UAVs, and even man-portable upon which the aircraft’s more malleable
electronic attack, standoff weapons, directed air defense systems—may be easier to find offensive and defensive capabilities—sensors,
energy, or other means. This approach, than passive radar. The adversary will likely weapons, and communications—are built.
however, would consume time and resources deploy substantial passive air defense assets, The concept of a layered defense will be criti-
and would likely fail to achieve low- to mid- and U.S. forces will face a long, tedious cal to the survivability of stealth aircraft in
altitude air superiority. process of locating and attriting them. the future.
ndupress.ndu.edu issue 55, 4th quarter 2009 / JFQ 141
FEATURES | Passive Radar and the Future of U.S. Military Power
Basic stealth techniques, however, will planners must recognize the counter to U.S. ■ work hand in hand with key allies to
be much less effective than they once were stealth-based air-superiority that is currently develop shared capabilities
against passive radar systems that benefit from unfolding, of which passive radar forms a core ■ explore enhancing parallel technolo-
bistatic geometry and the use of counterstealth technology. These self-same leaders must take gies (such as disposable transmitters).
waveforms. Increasingly, combatants will use appropriate measures to ensure that the United
passive radar and weapons systems to detect, States is not caught off guard by this impending Develop methods of degrading enemy
acquire, track, and target aerial stealth plat- shift in the technological landscape. The fol- passive radar. In support of this effort:
forms. Against such systems, stealth on its own lowing recommendations are in order.
will likely provide inadequate protection for Endeavor to be a leader in the passive ■ focus on a multilevel EW capability
manned aircraft, UAVs, and missiles. radar field. Arguably, the United States has against passive radar54
This article posits that an ongoing race marginalized the passive radar field due to ■ continue to develop layered defensive
between stealth and counterstealth is emerg- a focus on conventional radar systems. The measures for aircraft and UAVs.
ing, in which technology will provide only U.S. military must gain an understanding
incremental advantage to a combatant until of passive radar, not merely theoretically, or Prepare for military operations without
a new counter is found. This assertion does with minor research and development proj- air superiority. In support of this effort:
not mean that there are no further opportuni- ects, but with a dedicated effort. But why, one
ties to leverage stealth advantages, but that may ask, build a stealth counter when there ■ (again) develop passive radar, but
advances in stealth will be more evolutionary is no immediate stealth peer competitor? The in this case to deny enemy air superior-
than revolutionary. The future of stealth and answer is that would-be competitors in the ity—future enemy stealth capabilities are
counterstealth will more closely resemble the stealth arena are making a dedicated push to ultimately not a matter of if but when
technological one-upmanship that occurred develop this technology. We cannot afford to ■ continue to integrate complementary
during World War II and the Cold War than spend billions on stealth, only to fail to thor- piloted and unmanned system capabilities
the order of magnitude advantage the United oughly understand and counter rival systems. ■ plan and train to the contingency of
States enjoyed during the Gulf War and the two In support of this effort: military operations with only local air supe-
decades that have followed. Against a passive riority or with air superiority largely denied.
radar adversary, air superiority will likely only ■ build collaboration between key indus-
be achieved at significant cost. Forcible entry try and independent electronic engineers Passive radar will play a critical role
and amphibious operations will accordingly ■ increase prioritization of passive radar in future conflict. Ongoing advances in
prove much more challenging. Once again, the research and development passive radar will deny traditional means
defensive form of warfare asserts itself. ■ develop and field a passive radar of defeating enemy air defenses, make air
system on a U.S. training range—as a train- superiority difficult to achieve against a
Recommendations ing tool for U.S. stealth pilots and systems to passive radar opponent, and require changes
To best position the United States for test countermeasures and tactics and assess in thinking to maintain U.S. power projec-
the future, military strategists and operational performance53 tion capability.
we cannot afford to
spend billions on stealth,
only to fail to thoroughly
understand and counter
rival systems
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142 JFQ / issue 55, 4th quarter 2009 ndupress.ndu.edu
WESTRA
Will the United States go forward to hq.af.mil/Publications/fulltext/gulf_war_air_power_ 32 Willis and Griffiths, 95.
a future that resembles the past—one in survey-vol5.pdf>. 33 “Nebo-SVU Surveillance Radar (Russian
14 Ibid., 641. Federation)—Jane’s Radar and Electronic Warfare
which air superiority is gained only through
15 Benjamin S. Lambeth, “Kosovo and the Con- Systems,” available at <www.janes.com/extracts/
a gradual and costly reduction of the
tinuing SEAD Challenge,” Aerospace Power Journal extract/jrew/jrew0078.html>.
enemy—or to a future that is worse than the
16, no. 2 (Summer 2002), 12, available at <www. 34 “India Defense Consultants: What’s Hot—
past, in which the use of airpower is denied?
airpower.maxwell.af.mil/airchronicles/apj/apj02/ Analysis of Recent Happenings,” available at <www.
Alternatively, can the United States develop
sum02/sum02.pdf>. indiadefence.com/Rums_visit.htm>.
advantageous capabilities in passive radar, as 16 “Serb Discusses 1999 Downing of Stealth,” 35 Gerrit Dedden, “SMART–L Multibeam
well as effective counters to it, and so main- available at <www.usatoday.com/news/world/2005- Radar,” European Radar Conference 2004.
tain the airpower advantage? In this alternate 10-26-serb-stealth_x.htm>. 36 “The Leadership in Ukraine: Congressional
future, shaped by awareness of the shifting 17 Collin T. Ireton, “Filling the Stealth Gap and Record: October 17, 2002 (Senate),” available at
paradigm posed by counterstealth technology, Enhancing Global Strike Task Force Operations,” <http://frwebgate4.access.gpo.gov/cgi-bin/TEXTgate.
the United States can become a leader in the Air and Space Power Journal 20, no. 3 (2006), 69–76, cgi?WAISdocID=883061460628+1+1+0&WAISactio
available at <www.airpower.maxwell.af.mil/airchron- n=retrieve>.
passive radar field and, in cooperation with
icles/apj/apj06/fal06/Fal06.pdf>. 37 Guy J. Farley and S.M. Gauthier, “Radar
partner nations, position itself to maintain air
18 In this article, the term covert means stealthy Technology Forecast for Land Warfare,” April 2000,
superiority, accomplish its military campaign
or hidden versus the sense of preserving deniability, 8, available at <http://pubs.drdc.gc.ca/PDFS/zbd87/
objectives, and achieve its political goals.
as in covert operation, that is used in joint terminol- p514797.pdf>.
Which future will ours be? JFQ
ogy. In the F–117 downing, covert SAM employment 38 Willis and Griffiths, 132.
may have been accomplished through mobility, 39 Howland, 105.
NoTeS control of radar emissions, camouflage, and/or other 40 Ibid.
considerations. 41 “Silent Sentry Fact Sheet,” available at <www.
1 Passive radar is also known variously as 19 Ireton, 71. lockheedmartin.com/data/assets/isgs/documents/
passive coherent location, passive covert radar, and 20 B–2 and F–22 data are current as of April SilentSentry.pdf>.
passive bistatic radar. 2009. Joint Strike Fighter initial operational capability 42 “Super-Radar, Done Dirt Cheap,” available at
2 Carl von Clausewitz, On War, ed. Michael date is from Lieutenant General George J. Trautman <www.businessweek.com/magazine/content/03_42/
Howard and Peter Paret (Princeton: Princeton Uni- III, USMC, FY2009 Marine Aviation Plan: Supporting b3854113.htm>.
versity Press, 1976), 358. Our Most Lethal Asset (Washington, DC: Headquar- 43 “Homeland Alerter,” available at <www.tha-
3 Giulio Douhet, The Command of the Air, ters United States Marine Corps, October 1, 2008), lesraytheon.com/business-and-products/products/
trans. Dino Ferrari (Washington, DC: Office of Air 6–3, available at <http://hqinet001.hqmc.usmc.mil/ radars/passive-radars.html>.
Force History, 1983), 15. AVN/FY2009%20AVPLAN.pdf>. 44 Willis and Griffiths, 105.
4 “The Bomber Will Always Get Through,” Air 21 Christopher Bolkcom, F–35 Lightning II Joint 45 Ibid., 135.
Force Magazine 91, no. 7 (July 2008), 72, available at Strike Fighter (JSF) Program: Background, Status, and 46 Ibid., 107.
<www.airforce-magazine.com/MagazineArchive/ Issues (Washington, DC: Congressional Research 47 Ibid., 135.
Documents/2008/July%202008/0708keeper.pdf>. Service, February 17, 2009), 1, available at <www.fas. 48 Ibid.
5 Paul Howland, “Editorial: Passive Radar org/sgp/crs/weapons/RL30563.pdf>. 49 A.D. Lazarov and C.N. Minchev, “Three-
Systems,” IEEE Proceedings Radar, Sonar and Naviga- 22 “J–XX Stealthy Fighter Aircraft—(China Dimensional ISAR Image Reconstruction Technique
tion 152, no. 3 (2005), 105. stealth fighter),” January 3, 2008, available at <www. with Multiple Receivers,” Proceedings of 2d Inter-
6 Ibid. sinodefence.com/airforce/fighter/jxx.asp>. See also national Conference on Recent Advances in Space
7 “The Radar Pages—Chain Home,” available at Mari Yamaguchi, “Japan to Build Stealth Fighter Technologies, June 2005, 692.
<www.radarpages.co.uk/mob/ch/chainhome.htm>. Jets by 2014,” Air Force Times, December 10, 2007, 50 Willis and Griffiths, 104.
8 Howland, 105. available at <www.airforcetimes.com/news/2007/12/ 51 Ibid., 128.
9 Passive radar is considered a subset of bistatic ap_japan_stealth_071207/>; and “Indo-Russian 5th 52 Ibid., 178.
radar. Bistatic radar can also employ cooperative Generation Fighter to Take Off by 2012,” The Times 53 The author attributes the idea of a passive
(friendly) or noncooperative (enemy) transmitters. of India, October 30, 2007. radar training range to Paul Wiedenhaefer, interview
The British Chain Home radar and other radar 23 David Lynch, Introduction to RF Stealth by author, Arlington, VA, April 15, 2009.
fences are examples of early bistatic radars that (Raleigh, NC: SciTech, 2004), 3. 54 By multilevel, the author means that electronic
employed cooperative transmitters as dedicated parts 24 Ibid., 8. warfare should be considered tactically, operation-
of the system. 25 Ibid., 46. ally, and strategically. A multilevel electronic warfare
10 Craig C. Hannah, Striving for Air Superior- 26 Bill Sweetman, Inside the Stealth Bomber (EW) strategy could include both dedicated and
ity, vol. 76, The Tactical Air Command in Vietnam (Osceola, WI: MBI Publishing Co., 1999), 50. nondedicated EW platforms.
(College Station: Texas A&M University Press, 2002), 27 Nicholas J. Willis and H. Griffiths, Advances in
87. Bistatic Radar (Raleigh, NC: SciTech, 2007), 95–97.
11 “F–117A Nighthawk Factsheet,” available at 28 Bernardo Malfitano, “Low-Observable ‘Invis-
<www.air-attack.com/page/44/F-117A-Nighthawk. ible’ Airplanes: Radar Stealth,” available at <www.
html>. airplanedesign.info/52-radar-stealth.htm>.
12 “F–117 Site History,” available at <www. 29 Ibid.
f117reunion.org/f117_site_history.htm>. 30 Eugene F. Knott, John F. Shaeffer, and Michael
13 Eliot A. Cohen et al., eds., Gulf War Air Power T. Tuley, Radar Cross Section, 2d ed. (Raleigh, NC:
Survey (Washington, DC: Department of the Air SciTech, 2003), 58–59.
Force, 1993), 650, available at <www.airforcehistory. 31 Lynch, 36.
ndupress.ndu.edu issue 55, 4th quarter 2009 / JFQ 143