mountain top: beyond-the-horizon cruise missile defense

MOUNTAIN TOP: BEYOND-THE-HORIZON CRUISE MISSILE DEFENSE

TECHNOLOGY DEMONSTRATION

T

Mountain Top: Beyond-the-Horizon Cruise MissileDefense

William H. Zinger and Jerry A. Krill

he Cruise Missile Defense Advanced Concept Technology Demonstration,known as Mountain Top, was successfully completed at Kauai, Hawaii, during Januaryand February 1996. The demonstration featured a new type of cooperative engagementknown as “forward pass,” made possible by the Cooperative Engagement Capability, inwhich low-flying drones were engaged beyond the horizon of an Aegis ship for greatlyincreased engagement range. Although the Navy performed the forward passcooperative engagements alone, the Marine Corps, Air Force, and Army participatedin other major joint-services exercises. Most significantly, the concept of a surface-launched, air-supported engagement of cruise missiles was validated and has providedthe impetus for follow-on joint-services pursuit of an extended, beyond-the-horizonengagement capability for defense of land sites from land-, air-, and sea-based missiledefense systems. This article describes the background, objectives, conduct, and resultsof the Mountain Top test operations. Also detailed are the systems engineeringconcepts, system configurations, and the test and evaluation process that went into theplanning, conduct, and analysis of the many complex experiments of the AdvancedConcept Technology Demonstration.(Keywords: Beyond the horizon, Cooperative engagement, Forward pass, Joint services,Mountain Top, Overland cruise missile defense.)

BACKGROUNDThe concept of intercepting low-flying targets by

ship-launched missiles beyond the ship’s horizon withthe aid of an airborne platform was considered over twodecades ago. By removing the limitation of the ship’sradar horizon, such a concept envisioned the intercep-tion of targets much farther from the defended andengaging units, allowing time for additional engage-ments if necessary. Figure 1 illustrates the evolution ofthe “forward pass” concept.

The earliest version of the concept, examined atAPL in the mid-1970s as part of the Battle Group Anti-Air Warfare Coordination Program, embodied prima-rily the element of beyond-the-horizon guidance. In

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this case, a Standard Missile (SM) would be directedvia the ship’s missile midcourse control link to thevicinity of an F-14 fighter. The fighter’s fire controlradar, modified for this role, would illuminate the tar-get, allowing the missile to home on the reflected il-lumination from the target.

A modified form of forward pass emerged in the late1970s to early 1980s during a series of “outer air battle”studies, which addressed next-generation Navy battlegroup air defense requirements against Soviet bombersarmed with long-range antiship cruise missiles. If thebombers could be intercepted before they approachedto within range of launching their missiles at U.S.

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W. H. ZINGER AND J. A. KRILL

Mid-1970s Mid- to late 1980sLate 1970s to early 1980sFigure 1. Evolution of the forward pass concept, i.e., the concept of intercepting missiles attacking from beyond a ship’s horizon with theaid of airborne radars: in the mid-1970s, aircraft illumination of the target for missile semiactive homing; from the late 1970s to early 1980s,aircraft detection of the target and guided missile midcourse to multimode homing; by the mid- to late 1980s, aircraft detection of the targetand guided missile midcourse, and illumination of the target for pulsed semiactive missile homing.

ships, a critical new layer of defense would be provided.This variant of forward pass featured a conceptual, long-range ramjet missile that could be launched from anAegis cruiser and flown toward a carrier-based surveil-lance and fire control aircraft. The aircraft would carryadvanced, long-range sensors to detect bombers and totake over midcourse missile control from the ship viaan onboard aircraft-to-missile link. The missile wasenvisioned to have a multisensor homing seeker capableof locking onto a target from long distances. This formof the concept (Fig. 1, center) was known as “midcoursehandover” in contrast to the “remote illumination”approach of the F-14 concept. From these outer airbattle studies, in which APL was a prominent partic-ipant, a requirement for a long-range form of SM (nowknown as SM-2 Block IV) emerged along with the needfor a “cooperative engagement link.”

The Laboratory participated in yet another series ofrelated studies in the mid- to late 1980s, centeredaround the use of an airship to carry weapon systemelements comparable in function to the phased arrayradar and illuminators of an Aegis cruiser, but withreduced weight and new features for missile control.Key among those features was the use of a “multifunc-tion” phased array system as both the fire control radarand illuminator. This feature provided multiplexed il-lumination of targets, thus allowing simultaneous hom-ing of several SM-2 missiles. Analysis showed that,given sufficient equipment weight reduction and powercapacity, an airship so equipped and operating at analtitude of over 10,000 ft could greatly extend theeffective surveillance and engagement range againstlow-altitude cruise missiles.

This last example of forward pass can be seen as ahybrid between a remote-illumination forward pass anda form of cooperative engagement then being designedfor the Cooperative Engagement Capability1 (CEC; seethe boxed insert) known as engagement on remote data(EOR). An EOR capability allows a ship to fire an SM-2 missile and direct the missile midcourse and terminalhoming illumination using data from remote rather than

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own-ship sensors. For this concept, the airship wouldserve as both the remote data source for EOR and as theremote homing illuminator in the forward pass mode.This became the form of cooperative engagement con-sidered for the eventual Mountain Top tests.

With the end of the Cold War and the advent oflittoral environment scenarios, the low-altitude cruisemissile threat became even more important, so that abeyond-the-horizon intercept capability remained veryattractive. A variety of air platform candidates emergedincluding large tethered aerostats, wide-body aircraft,and a network of sensors from multiple smaller(manned or unmanned) aircraft linked via the CEC.An example of a concept using ship-launched aircraftnetworked with CEC is shown in Fig. 2.

MOUNTAIN TOP

DemonstrationThe potential operational advantages of a forward

pass capability led senior Navy and DoD officials toconclude in 1993 that the likely payoff of an airborneunit to extend surface-launched missile engagementrange was sufficiently compelling to explore as theinitial stage of an Advanced Concept TechnologyDemonstration (ACTD). This ACTD stage eventuallyfeatured two sets of test operations, which are describedin detail later in this article.

• Set 1 comprised beyond-the-horizon Navy tests (Phase1) and Army tests (Phase 2).

• Set 2, known as Enhanced Scenarios, involved par-ticipation of the Navy, Marine Corps, Army, and AirForce in joint exercises: arrival on the scene (Phase1), defense against shore-based attacks (Phase 2), andjoint littoral operations (Phase 3).

The organizations and participants in the ACTD arepresented in Table 1. (The boxed insert, APL Moun-tain Top Team, lists the Laboratory personnel whoparticipated in the formal testing.)

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Figure 2. Illustration of the land-attack cruise missile defense concept in which aircraft are networked via the Cooperative EngagementCapability to form a composite airborne surveillance and fire control radar/terminal illuminator capability. This allows sea- and land-basedunits to send an intercepting missile beyond the firing unit’s horizon. Engagement is thus possible at unprecedented ranges, therebyproviding extended defense against land-attack cruise missiles.

Table 1. Major players in the Mountain Top ACTD.a

Participant/organization Function

Navy CEC Program Manager ACTD program managementOffice of Naval Research Acting sponsorAPL and MIT Lincoln Labs Lead laboratoriesAPL Technical Direction Agent

for CEC and SM-2Raytheon E-Systems CEC prime contractorLockheed Martin Aegis prime contractorHughes Aircraft Co. SM-2 prime contractorNaval Weapons Support Center Equipment and site supportNaval Sea Systems Command Tartar fire control radar supportPacific Missile Range Facility Range operations support

aAegis and Standard Missile program offices also participated.

Patriotbattery

Track/illuminate

Search

Search

Aegisship

Aegis/Standard Missile-2midcourse

uplink/downlink

Cue

Patriotmissile

StandardMissile

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THE COOPERATIVE ENGAGEMENT CAPABILITYThe Cooperative Engagement Capability (CEC) has

been developed to network sensors and weapon systems ina manner that allows a set of geographically diverse airdefense systems of various types to operate as if they werea single entity, but with performance advantages that accruefrom the exploitation of their intrinsic diversities (i.e.,locations and sensor characteristics). A full description ofCEC is available in a previous issue of the Technical Digest.1

For the convenience of the reader, the primary CEC char-acteristics are briefly summarized here.

The CEC system consists of two subsystems: the Coop-erative Engagement Processor (CEP) and a data transferelement known as the Data Distribution System (DDS). InFig. A, the CEC is shown connected to the Aegis combatsystem, for example. The CEP provides its combatant’sweapon system with a composite track picture as well asrecommended target identity. This is accomplished by usinglocal and remote sensor measurements and informationfriend or foe (IFF) responses, which are exchanged via theDDS, to create a common air picture that is more completeand more accurate than one obtained from the best con-tributing sensor. With this quality information, a unit mayengage using only remote data, even if the target is fast andmaneuvering. The DDS performs the networking functionsof automatically establishing and maintaining a secure net-work for rapid exchange of target position measurements

and associated data messages among all cooperating com-batants.

The CEP on a given combatant is interfaced to its prin-cipal sensors, from which it receives radar or IFF targetreports and to which it provides data for special acquisitionor gating to acquire targets not locally held. All sensor orIFF reports associated with each assigned track are ex-changed via the DDS with other cooperating units. Theexchanged data include, as appropriate, target range, bear-ing, elevation, Doppler (if available), sensor type, and as-sociated track number. Unit position data obtained frominertial navigation data, DDS-to-DDS measurements, andother pertinent sources are also exchanged. The CEP grid-lock function computes the precise relative positions ofcooperating units and calibrates sensor angular and rangealignments by correlating reported positions of common,multiply tracked targets.

Using these data, the CEP develops an optimized com-posite track of each target by applying a quality-weightedcombination of all data sources via a Kalman filter. Con-tinual tests for target splits and merges are made at themeasurement input level. These track data are provided tothe combatant’s weapon system for fire control use and toits command/control element. The exchange and process-ing of unprocessed target measurement data—rather thanthe exchange of track data (with its inevitable lags andcorruption by fades), as is common to tactical link net-works—is a key feature of the CEC concept and is respon-sible for its ability to generate fire control–quality data forsensor/weapon acquisition and missile guidance.

The CEP also exchanges engagement status data amongcooperating weapon systems. In the future, it will computethe relative engageability of undesignated targets by thevarious weapon systems for recommendation of weaponsengagement assignments among networked units.

DDS elements, using their directive phased array an-tennas, automatically establish and maintain a communi-cation network among all cooperating units by synchro-nously switching their transmit and receive beams amongpairs of units in parallel (Fig. B). Because each DDS pos-sesses a phased array with a single beam for either trans-mission or reception, each unit can only point its beam toconnect (transmit or receive) to one other DDS at a time.Each connection event involves one unit transmittingthrough its beam to another unit and the other unit point-ing its beam at the transmitting unit to receive from it. Thistransmit/receive beam connectivity is generally performedin parallel among pairs in the network at precise times viathe DDS cesium clocks using a common, adaptive algo-rithm. Different pairings occur every “frame,” a small sub-second block of time. If a connectivity path or a unit is lost

CEC

Weaponcontrolsystem

SPY-1Bradar

IFF CEP

DDS

Command/decision

Displays

Command/control links

SPS-49radar

Figure A. CEC interfaces to the Aegis combat system.

ObjectivesThe Mountain Top ACTD management plan2 iden-

tified the Navy, Army, and the Advanced ResearchProjects Agency (ARPA) as the primary participantsand was approved by senior Army, Navy, DoD, andBallistic Missile Defense Organization officials.

The objective of . . . (Mountain Top) is to demon-strate the potential for significant enhancements to air

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defense capabilities by integrating Navy/Army/ARPAtechnology developments and existing air defense sys-tems. The goal is to detect, track, and successfully engagecruise missiles at ranges beyond the radar line of sightof surface-based air defense units, and provide an oppor-tunity to assess joint doctrine and concepts of air defenseoperation.2

Toward this objective the plan required an explora-tion of three new capabilities2:

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(e.g., because of equipment failure, excess jamming, orpropagation fade), the loss of connectivity is communicat-ed throughout the network, and the common algorithmsadjust the schedules and any relay sequences identicallyand automatically at each DDS.

Antenna directivity and relatively high transmitter pow-er provide the required countermeasures immunity andmargin against propagation fading, while maintaining a highdata rate and a low error rate. The phased array designpermits the near-instantaneous beam pointing necessary tomeet stringent subsecond timing requirements associatedwith sensor measurements. The utilization of a narrowbeam-directed phased array antenna for both transmission andreception is unprecedented for a mobile communicationsystem, as is the unique scheduling and control process usedby the DDS.

Transmit

Transmit

Receive

Receive

Time frame N + 1

Transmit

Transmit

Receive

Receive

Time frame N + 3

Transmit

Receive

Receive Transmit

Time frame N + 2

Time frame N

Transmit

Receive

Transmit

Receive

Because of these characteristics, the CEC provides theweapon system on every cooperating combatant with acomposite track picture that is more precise and containsmore rapidly updated target data than any individual con-tributing sensor. This is accomplished by the use of a sophis-ticated Kalman filter and the data flow logic of multiplesensor data, which exploit the more accurate range-versus-bearing data (for radars), eliminate target fades due to mul-tipath and refraction fades (especially over land), circum-vent main-beam jamming and local clutter, and utilize fa-vorable target aspect. In the case of elevated sensors, as inthe Mountain Top tests, the composite track also overcomesthe horizon limitations of own-ship radar for the firing unit.In addition, CEC obtains a force-wide assessment of targetidentity and engageability, greatly enhancing the cumula-tive effectiveness of the force.

Figure B. DDS directive pair-wise operation.

1. Increased target acquisition and tracking ranges (be-yond radar horizons) and extended target terminalillumination ranges through elevated sensor suites

2. Sensor networking along with a high data rate andfire control–quality data

3. Increased target engagement ranges


Measures of effectiveness for the Navy includedtarget detection and firm track ranges, fire controlconnectivity between an elevated site and the ship,missile intercept range beyond the ship’s horizonfrom the ship, inbound and crossing target trajectoriesrelative to the ship, and low target altitude above the

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APL MOUNTAIN TOP TEAMThe following APL staff and resident subcontractors (listed alphabetically) participated in the formal Mountain Top testing

during January and February 1996. The list illustrates the breadth and depth of the Laboratory’s involvement in those events.

CEC design, integration (land/ships/aircraft), test data evaluationG. P. AllynA. D. BernardJ. M. DavisG. P. GafkeR. W. GarretS. F. HaaseH. H. HamiltonL. M. HubbsS. A. KunclS. KuoG. K. LeeD. J. LevineR. E. MartinaitisT. A. McCartyR. C. McKenzieC. L. MyersJ. R. PenceR. W. ProueC. P. RichardsD. B. ScheplengM. Y. ShenL. W. ShroyerV. I. StetserJ. W. StevensO. M. StewartD. M. SundayP. H. TemkinD. I. TewellT. T. TranG. C. UeckerC. VandervestL. A. VentimigliaJ. WongC. A. Wright

Critical experiments, data collection,special instrumentation(some experiments were performed prior toJanuary/February 1996)R. A. BesekeA. J. BricM. H. ChenS. J. CrosbyG. J. DobekG. D. DockeryW. P. GannonW. R. GellerJ. GoldhirshJ. M. HansonA. S. HughesR. Z. JonesB. E. KlugaF. J. MarcotteJ. H. MeyerJ. J. MillerC. P. MrazekP. D. NacciJ. R. RowlandR. C. SchulzeR. M. WaterworthL. H. White

Documentation/photographyG. A. BoltzJ. G. FiskeR. L. GoldbergR. E. HallJ. E. O’Brien

Program management/liaisonC. J. GrantR. T. LundyM. MontoyaS. M. ParkerJ. E. Whitely

Senior managementR. W. ConstantineM. E. OliverG. L. SmithW. H. Zinger

Site design/installation supportL. J. AdamsR. BarryD. J. BuscherC. A. DalyH. F. DirksP. N. GarnerD. E. JohnsonM. H. LuesseL. E. McKenzieM. L. Miller

Systems engineeringW. I. CitrinJ. A. KrillP. E. LakomyJ. R. MooreJ. F. RediskeD. D. RichardsR. E. Thurber

Test preparation, coordination,conductC. R. CookA. F. JeyesG. LongM. R. SandsR. D. TimmN. E. White

sea surface at sub-Mach speed. A key purpose of theACTD, then, would be to validate the physics embed-ded in the forward pass concept and the performancecharacteristics of the equipment so that the resultscould be confidently applied to tactically orientedsystem development.

InstallationsMany considerations went into the planning, con-

duct, and evaluation of the Mountain Top ACTD. Insupport of the demonstration, APL, in collaborationwith Massachusetts Institute of Technology Lincoln

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Labs, proposed the following: Since available fire con-trol radar and illuminator elements were too heavy tobe carried by air vehicles, a mountaintop could be usedas a surrogate aircraft. This would allow existing shipand prototype aircraft equipment to be installed on anelevated site to emulate future airborne elements andfunctions.

A mountain site on the island of Kauai, Hawaii(Kokee Park), near the Pacific Missile Range Facility(PMRF) at Barking Sands, met all the foreseen require-ments. This site had three advantage: steepness, exist-ing government installations near the coast, and deepwater in which ships could operate safely near shore.

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The Kokee Park Site A, situated 3800 ft above sealevel, was an abandoned NASA installation. The Navyhad to establish appropriate electrical services, repairand upgrade the laboratory facilities, and erect specialtowers to support the radars and CEC (Fig. 3), whilemeeting the environmental standards of this famousstate park. Kokee also served APL and E-Systems as theprimary engineering data analysis site for the CECnetwork and as the base of operation for the radaragents, MIT, and the Naval Sea Systems Command.Aegis and SM-2 data analyses were performed by Lock-heed Martin and the Navy at Barking Sands. APL, incollaboration with the Navy, established data lines tothe primary test conduct and control site at BarkingSands to make the composite CEC track data outputavailable for test control.

The 1700-ft-elevation Makaha Ridge site, equippedwith the AN/SPS-48E (hereafter, SPS-48E) surveil-lance radar and IFF (information friend or foe), wasintegrated into the Kokee CEC system via fiber-opticlines. This enabled the elevated sites to more accurate-ly resemble the full avionics suite of the elevated firecontrol/surveillance aircraft concept, which would beexpected to provide a multiple-target tracking and IFFcapability. The integration scheme complemented thesingle-target tracking radar and fire control radar ele-ments at Kokee and provided for multiple mutual tar-gets with the SPY-1B radar of an Aegis cruiser for CECprecision gridlock (these and other defense units aredescribed in the next section).

To provide a and the Army PaDistribution Systboth the Kokee athe JTIDS was ininterface via a devAir Warfare Comminal was conne

The airport at helicopter equippsensors,3,4 the Cabelow), and theScenarios. Both ttethered at Barkiinfrared sensors terative, networketection of low-fly

Before describtechnical foundaresults were based

TECHNICAL

System ElemenThe weapon

Mountain Top bepresented in Tabparticipating in tfollowing paragra

Figure 3. Kokee Park “surrogate” aircraft site A, at a 3800-ft elevation. In addition toproviding the surrogate forward pass aircraft functions, test data evaluation of the siteelements and the CEC was conducted here. The system elements are described in the text.

RSTERroto-dome array

CEC array antenna

MK 74 fire control radarand illuminator area

Kokee site Aengineering test evaluation and

surrogate avionics facility

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ready surrogate “link” between CECtriot unit, Joint Tactical Information

em (JTIDS) terminals were installed atnd Barking Sands sites, i.e., at Kokeedirectly connected to the CEC displayice developed by the Naval Space andmand, and at Barking Sands the ter-cted to an existing Patriot interface.Barking Sands supported a commercialed with APL-developed atmosphericptive Seeker Lear aircraft (discussed

P-3 aircraft used in the Enhancedhe Makaha Ridge site and an aerostatng Sands were equipped with specialo provide insight into potential coop-d infrared systems for longer-range de-ing targets.ing the actual test operations, thetion upon which the Mountain Top is described in the following section.

FOUNDATION

tssystem elements participating in theyond-the-horizon ACTD (Set 1) are

le 2; Table 3 lists additional elementshe Enhanced Scenarios (Set 2). Thephs briefly describe the characteristics

of the CEC-networked weaponsystem elements.

CEC: Sensor and Fire ControlNetwork

As noted in the boxed insert, theCEC was developed to allow a net-work of air defense units to inte-grate their collective sensor mea-surement and weapons control dataso as to operate as a single, distrib-uted air defense system. For theACTD, two specially adapted CECequipment sets were built, one forthe Kokee surrogate aircraft siteand the other for the USS Lake Erie(Aegis CG 70). The CEC electron-ics differed somewhat from thepermanent ship sets installed onthe USS Anzio and Cape St. George(Aegis CG 68 and 71, respectively)to reduce weight and facilitatehousing in a shelter. A follow-oncruise missile defense (CMD) phase

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Table 2. Major beyond-the-horizon test elements (Set 1).

Element Type Function

Radar surveillance Pulsed Doppler array Stationed at elevated sight to perform targettechnology experimental radar surveillanceradar (RSTER)

Mark 74 (MK 74) Tartar fire control radar Stationed at elevated site to provide precisiontarget data and target illumination

SPS-48E Terrier New-Threat-Upgrade Stationed at elevated site to provide three-dimensional radar surveillance and gridlock data

CEC Cooperative engagement/ Networked radars and illumination to weaponsensor network control for composite track picture and

cooperative engagement

USS Lake Erie Aegis, CG 70 Provided engagement control and missilelaunch/guidance

SM-2 Block IIIA Guided missile Responded in-flight to midcourse(instrumented) commands and performed semi-active

homing and warhead fusing

BQM-74 Drone Controlled from elevated sight; flown withcharacteristics of a low-altitude attacker

Table 3. Major additional elements used in the Enhanced Scenarios (Set 2).

Element Type Function

USS Anzio and Cape St. George Aegis, CG 68 and 71 Varied depending on scenario, including(with CEC) data collection and cooperative

SM-2 engagements

Hawk Marine Corps anti-air Provided engagement control and missileweapon system launch/guidance for Hawk missile firings

TPS-59 Hawk radar Provided elevated surveillance

Aerostat Tethered, unmanned airship Supplied elevated digital communicationrelay for Hawk firings and infraredsensor test vehicle

AWACS Air Force airborne warning Collected surveillace radar data andand control system reported tracks over JTIDS

P-3 U.S. Customs Service surveil- Served as part of the CEC net withlance aircraft (with CEC) surveillance radar

Patriot Army surface-to-air Collected radar data; reportedmissile system tracks over JTIDS

BQM-74/-37 Target drones Served as SM-2 and Hawk firingscenario targets

JTIDS Link 16 Tactical data link Provided command/control link

F-15/F-16 Air Force and Air Served as scenario red and blue forcesReserve fighters

Big Crow and Q-Lear Electronic warfare test aircraft Served as electronic warfare threats(jammers)

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is being planned, which will feature a next-generationpreproduction E-2C version of the CEC equipmentcalled the “common equipment set.” This set has iden-tical electronics for surface and air units, yet conformsto the more constrained airborne payload. Reference 1discusses the differences between these versions.

Functionally, the CEC for this demonstration was aderivative of the version used during 1994 develop-ment testing2 with the addition of hardware and soft-ware for interfacing with radar surveillance technologyexperimental radar (RSTER) and the Mark (MK) 74tracking illuminator.

RSTER: Advanced Airborne Surveillance Radar

RSTER was developed for ARPA by MIT LincolnLabs to evaluate experimental Doppler radar technol-ogies. For this demonstration, RSTER was installed atthe Kokee site to provide the required horizon detec-tion range performance and was fitted with a prototypeadvanced E-2C phased array antenna in a “roto-dome”configuration. The system search and track softwarewas also modified by MIT for the ACTD to significant-ly increase the update rate, so as to minimize track filterlag errors due to target maneuvers and to ensure earlierdetection through shorter search frame times.

Aegis: Air Defense and Combat System

Aegis ships were the primary air defense forces inmost Mountain Top scenarios. The Aegis air defenseweapon system uses the multifunctional SPY-1B phasedarray radar to perform the search, track, and fire controlfunctions. The CEC-integrated version of the Aegisweapon system that was a derivative of the Baseline 4computer programs1 was used with minor modificationsto meet ACTD requirements. This version had beendemonstrated to enable the Aegis system to perform anSM-2 engagement on a target, even when the firingship’s SPY-1B radar did not track the target, by usingfire control radar data from another ship via CEC. Thistype of cooperative engagement, i.e., EOR, was de-scribed earlier in this article.

Tartar MK 74: Surrogate Airborne Fire ControlTracking Radar and Illuminator

The Aegis system with CEC had already beenmodified to accept remote fire control radar data fromeither another Aegis radar or from a fire control radaron Tartar New-Threat-Upgrade (NTU) ships that sup-port a different version of SM-2.1 For testing in 1994,the Tartar system had also been integrated with CECand was able to meet the engagement range objectivesof the management plan with remote data, serving as


either a source or a firing unit.1 For this ACTD, theTartar MK 74 missile fire control system installed at theKokee site served as both the fire control radar sourceand the terminal homing illuminator for the Aegis SM-2, in the same manner as it serves as both radar andilluminator on a Tartar ship for a Tartar configurationof SM-2. Modeling indicated that the MK 74 met therequired fire control radar detection range and hadsufficient illumination power for a modified SM-2missile to achieve the intercept range well beyond theship horizon, even if the ship was 25 nmi forward ofthe illuminator. Relatively minor changes were madeto this element, mainly to make it compatible withRSTER cueing accuracy and with negative, look-downtarget elevation angles (owing to its mountain altituderelative to the horizon). Figure 3 shows the MK 74system, RSTER, and CEC antenna as part of the Kokeesite installation.

SM-2 Block IIIA with Experimental Modifications

The latest-generation SM-2 in the Fleet is the BlockIIIA, which, like Block III, has exhibited a very highintercept success rate. As will be noted in the nextsection, a beyond-the-horizon geometry and an elevat-ed illuminator produce much greater sea reflectionthan seen in normal low-altitude engagements. There-fore, to reduce clutter interference, Hughes Aircraftmodified the IIIA seeker by incorporating the “Plate 1receiver upgrade” under development for the next-generation Block IV. The missiles were also furnishedwith a telemetry package to transmit terminal homingsignals to determine intercept performance.

Systems Engineering ApproachThe systems engineering process used to develop the

distributed Navy forward pass weapon control network(consisting of Aegis/SM-2, CEC, and the mountaintopradars and illuminator) entailed all participating orga-nizations in extensive analysis, experimentation, andplanning extending over a 30-month period. Figure 4shows this process as it applied to Mountain Top. Be-cause of the diversity of program offices involved, eachwith their respective engineering teams, a systems en-gineering working group was formed under the coordi-nation of the CEC program to ensure that design andinterface issues were identified and resolved as the prin-cipals proceeded to design, review, and document thenetworked system. Issues included the ship and missilelaunch safety zone requirements for the PMRF range,types of drones, availability of systems (such as theversions of SM, Aegis ship combat system, and moun-taintop illuminator), and the local geological features.

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ACTD management plantop-level requirements

Interface specificationsFunctional/performance

allocations

Critical experiments and modeling

Fabrication/modification Integration tests

Site andpreparatory tests

Formal ACTD tests

Figure 4. The systems engineering process as applied to the Mountain Top ACTD, beginning with the concept and requirementsdefinition, proceeding through requirements allocation to the elemental level, and finally to testing from the smallest elements up to thefully networked composite system. APL provided leadership in modeling, requirements definition and allocation, interface specifications,critical experiments, site risk reduction scenarios, site subsystem checkout and verification, and test conduct. Shown in the formal ACTDtest inset, from right to left, are APL’s Test Conductor, Art Jeyes, sitting beside the CEC and Mountain Top Program Manager, MichaelO’Driscoll, and RADM Timothy Hood, the Program Executive Officer for Theater Air Defense.

The primary system models and simulations thathave been used through the years by the variousprograms were adapted to this effort. Because themodels had been previously validated with test dataand broadly used, the systems engineering team hadmuch confidence in them. As will be discussed later inthis article, test results were very close to the modelpredictions.

Since CEC provided the means to effect theACTD’s “distributed weapon system,” the role of APL’sTechnical Direction Agent (TDA) extended to tech-nical coordination in carrying forward the netted sys-tems engineering process. Since the Laboratory is alsothe TDA for the SM-2 and Tartar NTU programs, andserves as technical advisor to the Aegis program as well,it was involved on both sides of the CEC interfaces.

Analysis

Analysis prior to the Mountain Top demonstrationshowed that

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• Sensors and fire control could provide adequate rangeperformance against the spectrum of atmospheric andsea conditions experienced around Kauai.

• CEC network and missile error budgets would permitmidcourse guidance with acceptable errors for a suc-cessful terminal homing phase.

• Missile seeker pointing errors at the start of terminalacquisition were sufficiently small to support targetacquisition.

• The Block IIIA version of SM-2 possessed sufficientkinematics to support stable flight and terminal con-trol at the ranges and altitudes of interest.

• The Block IIIA would be able to acquire and track adrone-sized target in the expected sea clutter back-ground if modified with the Plate 1 upgrade to sup-press clutter interference.

Missile Captive Seeker Critical Experiments

In the course of the SM development program, APLhad performed critical Captive Seeker5 experiments for

S HOPKINS APL TECHNICAL DIGEST, VOLUME 18, NUMBER 4 (1997)


a variety of sea- and land-clutter conditions to deter-mine the effects on seeker performance against low-flying targets. These experiments showed that, basedon Mountain Top geometry, steeper illumination inci-dence angle to the sea, longer range, higher surfacereflection, and different Doppler characteristics, themissile receiver would require special filtering com-pared with a conventional engagement. The Plate 1upgrade had already been developed for the longer-range Block IV missile, and performance modelingindicated that it would also suffice to allow the BlockIIIA seeker to distinguish the illumination reflectionfrom the target relative to that from the sea surface forthe Mountain Top geometry. However, only limitedexperimental data existed to support this conclusion.

To capture the seasonal sea and atmospheric char-acteristics to be encountered, the Captive Seekerexperiment was conducted about a year before theACTD. Another Captive Seeker test series was alsoperformed for the actual engagement geometries andtargets several months before the firing events. Bothsets of test results confirmed that Block IIIA, modifiedwith the Plate 1 clutter filter, would be effective underMountain Top conditions.

Radar Experiments

The foregoing analysis and systems engineering ef-forts were augmented by risk reduction assessments andother critical experiments for key aspects of the dem-onstration, e.g.,

• The acquisition, track, and illuminator power densityof the MK 74 system were examined for the geometryof each of the planned beyond-the-horizon en-gagement scenarios using the Captive Seeker systemagainst drones.

• The acquisition and track performance of the RSTERradar was tested for the geometry of each plannedengagement.

• The modifications required to the Aegis combatsystem were analyzed, defined, and then tested at theAegis combat system engineering development site.

Test and Evaluation Process

Test Engineering

As a complement to the systems engineering pro-cess, a test and evaluation working group was formedearly in the Mountain Top preparation effort. Thegroup worked out such issues as

• Impact on engagement range due to range safetyrequirements

• Selection of the Kauai mountain ridge with sufficientheight to achieve required range to the target horizon


• Hawaiian state park environmental requirements forvisual, electromagnetic, and acoustic noise effects

• PMRF requirements to provide drone control out tothe required ranges (resulting in the developmentof a new long-range drone control system for thispurpose)

• Selection and preparations of the BQM-74 droneswith the requisite characteristics

Scenarios were defined in terms of inbound trajec-tories and engagement geometries in accordance withthe systems engineering design, and were embodied ina series of test and evaluation planning documents(e.g., Mountain Top installation plan and installationdocuments, PMRF plan, requests for test assets, testplan and procedures, and data evaluation plan). TheNavy Program Office directed APL to conduct the testseries.

Test Planning

The next level of detailed preparations includedscheduling site preparations, ship installations, testsupport assets, and test range services as well as assess-ing ship availability requirements for checkout, re-hearsal, and test. Testing began at the subsystem level,for example, starting with the SPY-1B computer pro-gram and the CEC processor modules, proceedingthrough interface tests, and finally testing the entireCEC network of systems (Fig. 4). These tests wereperformed at the sites of the design agents (see Table1). Interface tests were generally performed betweenCEC and weapon system elements at the combat sys-tem test sites using APL-supplied wrap-around simula-tors. Finally, network-level tests were performed atPMRF. Key decision points for the higher-level eventswere formal test readiness and control panel reviews,missile firing scenario certification review, and a weap-on safety review. The final reviews were chaired bysenior Navy officers.

BEYOND-THE-HORIZON TESTS

Phase 1: Navy Firing TestsThe Navy tests consisted of a series of firing exer-

cises by an Aegis ship (USS Lake Erie) against a low-flying drone (BQM-74 representing a simulated enemytarget). Remote target radar data were used along withillumination by radars mounted on the Kokee site radarsurrogate “aircraft.” The integration of the target datafrom the elevated site into composite fire control–quality tracks was accomplished by CEC. The test con-figuration is illustrated in Fig. 5, which represents theCMD concept shown in Fig. 2. Not shown is the SPS-48E three-dimensional surveillance radar at the lowerMakaha Ridge site that provides target identification

1997) 511


Kokee site

Aegis CGmissile initialization

and midcourse

Aegis/SM-2midcourse

uplink/downlinkStandard

Missile

MK 74

CEC

Track/illuminate

Search/cue

Composite trackdevelopment

BarkingSands

BQM-74

Patriotradar

SPY-1B radar horizon

Joint TacticalInformatiomDistribution

System

RSTER

Figure 5. Conceptual representation of Mountain Top tests configured to represent the cruise missile defense concept depicted in Fig. 2.

and data to enable CEC to precisely gridlock the systemelements relative to one another.

Test Sequence

The sequence for each of the beyond-the-horizonfiring events was as follows (also see Fig. 6):

1. The CEC established gridlock (precise relative sensoralignment and position of scenario elements) fromarea targets seen by both the land site and ship. CECunits at the land site and ship performed (independentbut identical) composite tracking and identificationfrom distributed radar and IFF data.

2. The BQM-74 drone was launched from the BarkingSands site, flown outbound for 80 nmi, turned in-bound, and descended to low altitude.

512 JOH

Figure 6. Representation of the sequence of the initial beyond-the-horizon engagement. The plan view indicates a low-elevationinbound drone approaching the Kokee site with a crossing targetintercept by the ship-launched SM-2 (not drawn to scale).

Niihau Kauai

Pacific Missile Range Facility

USS Lake Erie

Kokee Park

Barking Sands

Plannedintercept point

Nor

th/s

outh

rang

e re

lativ

e to

Kok

ee

East/west range relative to Kokee



3. RSTER detected the drone and passed measurementdata to its land-site CEC. The CEC passed measure-ments to the ship. Both CEC units (land andship) independently derived the track of the dronetarget.

4. Aegis commanded the drone to be engaged. From theengagement command, CEC cued MK 74 to acquirethe target. Both CEC units performed compositetracking of the drone using RSTER and the moreaccurate MK 74 data. CEC provided target measure-ment data from the MK 74 to the ship.

5. The ship launched an SM-2 missile at the target, thenguided SM-2 via its midcourse link to within terminalhoming range using CEC target data for fire control.

6. The CEC commanded MK 74 to illuminate thetarget. The ship commanded the missile to beginhoming. The missile intercepted the target.

Test Results

For the initial scenario event, the drone approacheda fictitious target on the beach, where it was intercept-ed by the SM-2 well beyond the ship’s horizon and wellprior to the target area. The missile not only passedwithin lethal range of the drone but scored a direct hit.Figure 7 shows the composite track picture created byan automated data reduction system based on CEC datacollected at the Kokee site. This was the first-everengagement of a low-altitude target beyond the firingship’s horizon.

The distributed missile control between the ship andmountain site had been comparable in intercept per-formance to the best that could be expected of conven-tional, ship-only engagements, yet at a range manytimes that possible by the cruiser against such a targetwithout the elevated elements. Furthermore, thepredicted SM-2 seeker characteristics, the detailedmodels of detection and track performance of the

SM-2

Intercept

Kokee site A

RSTER

MK 74

Figure 7. Data reduction plot of tracks from the first beyond-the-horizon firing. The track histories of the drone and the interceptingmissile are shown. The histories terminate at the intercept pointwhere the missile impacts the drone. As the engagement isordered by the ship, the MK 74 automatically is cued from theRSTER data and acquires the target. MK 74 data are used formissile guidance via the ship.


mountain sensors, and the simulated missile fly-outpredictions were very close to actual event results.

Another scenario event (Fig. 8) featured the droneflying toward the ship and crossing relative to the is-land mountaintop sensors. The missile made a success-ful intercept and damaged the target. Again, the inter-cept range was well beyond the firing ship’s horizon andvery close to model predictions.

The final forward pass scenario of this set of eventsentailed aligning the drone approach path with theship and the mountain. Although the geometry wassimpler (i.e., the drone was inbound and not crossingwith regard to the ship and mountain site), detectionand engagement presented a greater challenge becauseof predicted multipath propagation fading. However,the missile again successfully intercepted the target.The engagement range was close to the maximum thatmodeling indicated to be achievable for the test con-ditions and system elements used.

This final test highlighted an important feature ofthe CEC design: When the ship first ordered an engage-ment, causing the CEC to cue the MK 74 fire controlradar from RSTER data, the MK 74 could not acquirethe target because of a (predicted) multipath fade atthat range. The CEC unit on the mountain reported tothe ship CEC that the required remote data could notbe provided at that time. The ship operator, so alerted,ordered the engagement again, by which time the dronehad flown out of the fade region, thereby enabling theMK 74 to acquire and support the successful intercept.

These tests met and exceeded all objectives. Allthree low-flying targets were successfully intercepted atranges well beyond those possible with a single ship.The tests demonstrated the technical feasibility ofproviding a Fleet-wide ability to defend inland targetsagainst low-flying cruise missiles using special aircraft(or aerostat) systems to greatly extend each ship’s en-gagement horizon.

RSTER

MK 74SM-2

Kokee site A

Intercept

Figure 8. Data reduction plot of tracks from the second beyond-the-horizon firing (see Fig. 7 caption).

997) 513


Phase 2: Army ExperimentsThe Army was unprepared as of 1996 to conduct

firing tests comparable to those of the Navy. Their plan,therefore, called for simulated engagements and captiveseeker experiments to test the potential of forward passintercepts by a Patriot weapon system. Elements ofthe simulations and experiments were the PatriotPAC-3 weapon system located at Barking Sands (Fig. 5),a computer simulation of the missile, and the aircraft-mounted advanced Patriot Extended-Range InterceptTechnology Missile (ERINT) captive seeker carriedaboard a C-130 aircraft to simulate target engagementsagainst low- to mid-altitude drones.

For this phase, the CEC composite track data weretransmitted from the Kokee site to the Patriot via aJTIDS communications link using a “link all-purposeworkstation” interface unit to translate CEC messagesto JTIDS format. From Patriot, the composite data weresupplied to the simulation and linked to the captiveERINT seeker.

These Army simulations were successful, demonstrat-ing that the target would have been intercepted in a highpercentage of cases.6 For each ERINT seeker test, thePatriot unit was able to cue the captive seeker to acquirethe target on the basis of CEC composite track data.

ENHANCED SCENARIOSFor Set 2 of the Mountain Top ACTD operations,

Enhanced Scenarios, two additional CEC-equippedcruisers from the Atlantic Fleet and a CEC-equippedU.S. Customs Service P-3 aircraft were brought in toprovide greater opportunities for joint, extended airdefense experimentation. With participation by an AirForce AWACS test aircraft, a total of three Aegis shipsequipped with CEC, a Marine Corps Hawk system(modified to accept fire control cues via CEC fromAegis and mountain sensors), the P-3, and an ArmyPatriot site, a truly all-service experiment under care-fully controlled test conditions was made possible.During this stage of Mountain Top tests, the Navy andAPL worked closely to establish the test objectives anddesign and certify the scenarios, which were subse-quently agreed to by the other services. Those objec-tives aimed

• To provide further risk reduction opportunities forthe upcoming CEC initial operational capability(IOC), i.e., formal Fleet deployment, later that year

• To provide an opportunity for further CEC datacollection in support of new tactics development andnew concepts

• To afford an opportunity for joint-services participa-tion in a littoral setting with exploration of sensor andweapons networking (via CEC) and command/control networking (via JTIDS)

514 JO

Sequence of Operational ScenariosAgain, the Enhanced Scenarios comprised three phases:

1. Arrival on the scene: Aegis ships—the Cape St.George, Lake Erie, and Anzio—and the CustomsService P-3 equipped with CEC arrived on the scene(Fig. 9a). The CEC network established a compositearea picture.

2. Defense against shore-based attack: the Army’s Pa-triot battery and the Air Force’s AWACS joinedoperations (Fig. 9b). Simulated air attacks werelaunched against forces.

3. Joint littoral operations: Joint-service operations withparticipation of the Navy ships, P-3, Patriot, Hawk,AWACS, and fighters (Fig. 9c). Enemy jammersattacked nearly all radars.

Phase 1: Arrival on the Scene

This initial phase featured two experiments that weredesigned to provide data to support the development of

Figure 9. Enhanced scenarios: (a) Phase 1, arrival on the scene;(b) phase 2, defense against shore-based attack; (c) phase 3, jointlittoral operations.

P-3

USS Lake Erie

USS Anzio

SPS-48E

F-16s F-16s

Radarsectors

(a)

Patriot

Drones

P-3

AWACS

Jammer

Silent shootertarget

(b)

AWACS

Patriot

F-16s/15s

F-15s or C-12s

F-16s/15s

F-16s

P-3

Jammers

USS Lake Erie

USS Anzio

HawkTSP-59/

firecontrol

(c)

USS CapeSt. George

USS CapeSt. George

Kokee

Kokee

Kokee

HNS HOPKINS APL TECHNICAL DIGEST, VOLUME 18, NUMBER 4 (1997)


advanced CEC functions. The first experiment involvedthe three Aegis cruisers, the Kokee site, and the P-3aircraft in the CEC network. Its objective was to collectdata relevant to the ability of CEC to allow radar cov-erage coordination. In severe clutter or jamming oragainst difficult targets (e.g., future tactical ballisticmissiles), units equipped with CEC may each elect tocover only certain sectors with their radars to cooper-atively manage available transmitter energy and retainappropriately short search frame times. These sectorsmay be coordinated via CEC. In that case, if a unitdetects a target in its sector, the other ships’ radars maycue off the data, or one of the other ships may evenengage the target using the detecting unit’s data (i.e., anEOR). The data collected in these tests indicated thatthe units were effectively positioned to uncover regionsblocked by terrain. Thus, although several tracks wereonly held by certain units at a time (because of blockage,sectoring, etc.), CEC allowed all networked componentsto process the collection of radar measurement data fromall other CEC units with accuracy comparable to orbetter than the sensors themselves. As tracks transi-tioned between sensors, composite track continuity (interms of position, velocity, identification, and compositetrack number) was maintained.

The second set of experiments in Phase 1 was per-formed to collect data for laboratory testing of a newcapability that was introduced in CEC for its IOC thatoccurred later in 1996. This capability integrates radarpassive angle (PAT) data from targets emitting radia-tion in the radar band into the CEC composite trackingprocess. The new algorithms associate PAT measure-ments with CEC track data and associate PAT datafrom two or more units to derive range and bearing aswell as elevation angles as outputs of the CEC filter(analogous to passive range triangulation). A “deghost-ing” algorithm also acts to resolve multiple jammers toobtain a unique aircraft location of each or an indica-tion that insufficient data are available to do so. Con-firming previous analyses, the radar passive range com-posite track was of sufficient quality that it couldsupport missile engagements over a wide range ofemitting target positions relative to the tracking ships.This capability for missile engagements from passivecomposite track data is planned for future incorpora-tion into CEC and Aegis.

Despite test curtailment due to extremely severeweather, some very useful data were collected, allowinglaboratory evaluation of the real-time passive trackingprocess. The data supported both PAT-to-active trackassociation and passive ranging, as shown in Fig. 10. TheIOC package did, in fact, successfully field the new CECpassive range tracking capability. In addition, data col-lections from all units were obtained to support furtherCEC and JTIDS network architecture assessment.


Passiveonly track

Radiating aircraft 1

Passive/activetrack

Radiating aircraft 2

Active track

Figure 10. Passive ranging scenario. Shown are the track historiesfrom two separate aircraft emitting radiation in the radar band forwhich the cruisers each obtain a passive angle track (without therange dimension). The data collected from the passive rangingscenario were replayed through the next-generation CooperativeEngagement Processor tracker several weeks after the event toconfirm the process for the subsequent CEC initial operationalcapability (IOC). The CEC IOC track filter used active (three-dimensional) and passive (two-dimensional) track measurementdata to generate highly accurate three-dimensional composite tracks.

Phase 2: Defense Against Shore-Based Attack

These scenarios consisted of several simulated andactual missile engagements. The first event demonstrat-ed the ability of CEC to provide high-quality compositetracks in the presence of various forms of electroniccountermeasures against the networked sensors.

The second scenario demonstrated CEC’s ability tosupport the Navy’s “silent shooter” tactic. In this tac-tic, one or more ships are stationed at positions thatgive them good engagement coverage of regionswhere hostile missiles or aircraft might attempt topenetrate. These ships operate in an “emissions con-trol” state with radiating systems off (at least in theexpected penetration sector). They are linked by theCEC network to ships with active radar located wherethey could only be reached by hostile forces if theyflew through the area guarded by the silent units. Asilent ship, knowing the enemy’s precise location viathe CEC network, could launch an SM-2 missile toengage the target, without ever enabling radar search,using remote data from the network to directmidcourse guidance and target illumination. If theengagement could be completed before the firingship could be detected, a very effective silentshooter capability would result. The simulated en-gagements by the “silent” ship in this scenario provid-ed valuable data for future system design and tacticsdevelopment.

997) 515


Two missile firing scenarios were also executedduring this phase. To increase range safety margins forthe multiple ships participating, drone targets operatedat altitudes above those used in the beyond-the-hori-zon tests. Instrumented SM-2 Block III missiles wereused. In one scenario, BQM-34 drones were flownsimultaneously at two cruisers, with a third cruiser offto the side. The objectives of this scenario were two-fold: (1) to provide two simultaneous engagements onremote data with the same remote data source (for thefirst time), and (2) to collect data for a risk reductionevaluation of a new coordinated engagement algo-rithm known as “first launch” (invented by the Aegisprime contractor, Lockheed Martin, while under APLsubcontract in the mid-1980s).

The first launch process was incorporated in theCEC IOC package in 1996. When enabled by anoperator, this feature allows the first ship to order an

engagement to report over CEC, so that the other shipremoves the target from its immediate engagementqueue, thereby minimizing unwanted, redundant en-gagements. The test event culminated with successfullaunches and engagements by the Anzio and Cape St.George using remote data from the Lake Erie. Theengagements were so well coordinated by the firingships that the intercepts occurred nearly simulta-neously. Figure 11 is a snapshot of the CEC displayof the event during the midcourse phase of theengagement.

In a similar firing scenario, the Anzio engagedand successfully intercepted a pair of targets using re-mote data from the Lake Erie. This was the first occur-rence of multiple engagements by a firing ship usingremote data and was scored as a success (Fig. 12).In all, there were five successful SM-2 Block IIIEOR firings.

516 JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 18, NUMBER 4 (1997)

Figure 11. CEC snapshot of dual cooperative engagement events by two firing ships—the USS Anzio (CG 68) and Cape St. George (CG71)—engaging drones using the USS Lake Erie (CG 70) SPY-1B remote data. The triangles are the drone targets. The CEC-equippedunits are circles. The upper-half squares near the drones are SMs in flight.The dotted lines between CG 70 and the targets indicate thatCG 70 is the source of fire control data. The solid lines between CG 68 and 71 and the drones indicate the target/ship engagement pairings.The thin solid lines indicate direct CEC connectivity among CEC units.

ND-THE-HORIZON CRUISE MISSILE DEFENSE
MOUNTAIN TOP: BEYO
Figure 12. CEC data reduction plot of dual drone cooperative engagements by a singleship. The track histories of the drones were obtained by the USS Lake Erie (CG 70), whichwas the source for dual engagements on remote data by the Anzio (CG 68).

Phase 3: Joint Littoral OperationsThis final phase of the Enhanced Scenarios provided

an opportunity for the CEC-equipped ships, P-3 air-craft, and the Kokee site to operate with joint elementsin a common scenario. The Navy units were intercon-nected by the CEC and to the Army and Air Force bythe JTIDS. The first all-services operations using atactical Model 4 JTIDS network were conducted.AWACS radar data were collected in these operation-ally representative situations simultaneously with CECnetwork data as a basis for beginning development ofrequirements and a design concept for integration ofAWACS into the CEC network. TPS-59 radar datawere collected for the same purpose. Development workusing these data has begun. The CEC network tracksof several “two-on-two” F-15/ 16 air combat operationswere conducted. These composite tracks were formedby the radar and IFF equipment on the three Aegiscruisers and the P-3, with no loss of track identity orcontinuity, even though significant main-beam radarjamming was present.

The primary scenario consisted of 12 fighters, halfdesignated blue force and half red force, to conductoperations in concert with airborne electronic counter-measures against participating radars. It was first run withthe CEC operating using a specially defined composite

and relayed throuusing a single-chasurrogate CEC Dainsert). The compfrom the three Ae14 illustrates the cments were succesradar cues from CMakaha Ridge (re

As part of the fodata have since beat APL and integrFigure 15 is a CEtrack history for dmissile firings. Thalthough not fully revealed the potenradar to the Navy tage point, the TPSdetected by the othof the drone launchhave provided fortarget by one of actually been in thinitial step towardand CEC, which

Jammeraircraft

Outbounddrones

Inbound drones

Missile track

Kokee site ACG 68CG 70

CG 71

AWACS track


identification doctrine and CECtracks reported over JTIDS onlyfrom the Kokee site JTIDS unit(others were in a receive-only con-dition) to represent the near-futureCEC/JTIDS interoperability archi-tecture. This architecture will fea-ture CEC sensor-networked identi-fication doctrine in accordancewith JTIDS-promulgated com-mand/control doctrine as well asJTIDS reporting of CEC compositetracks for greater track life andmore consistent track number andidentification correlation. Figure13 is a data reduction plot of theevent midway through the scenar-io. A second “without CEC” run ofthis same scenario allowed theunits to operate the first truly jointJTIDS Link 16 protocols with thethree cruisers, AWACS, and Patri-ot in the network.

Also as part of this phase, theHawk battery conducted live firingsagainst drones. The scenario con-sisted of a BQM-74 drone withtowed targets inbound toward thebattery. For one firing, the compos-ite track data were supplied by CEC

gh the aerostat, mentioned earlier,nnel ground-to-air military radio as ata Distribution System (see the boxedosite track consisted of sensor data

gis cruisers and the Kokee site. Figureonfiguration. All five Hawk engage-

sfully executed with either fire controlEC or from the TPS-59 radar on

presenting an elevated sensor).llow-on evaluation, collected TPS-59

en processed through a CEC processorated into the composite track picture.C display snapshot of the compositeata collected during one of the Hawke resulting composite track picture,

optimized to specification at that time,tial contribution of such a land-basedCEC network. From its elevated van--59 provided radar data of a target noter CEC units as well as early detection from Barking Sands. The latter would

automatic special acquisition of thethe Aegis radars if the TPS-59 hade CEC network. These results were an the integration of the TPS-59 radarwas achieved in 1997.

997) 517


Figure 13. CEC data reduction plot of a complex joint operationsscenario. The composite track histories of the scenario are shown.Tracking and identification continuity were maintained throughout,and the CEC composite tracks were reported over JTIDS from theKokee site. The colors in the track histories correspond to thecolors of the CEC units indicating the portions of the track contrib-uted by each unit.

USAFAWACS and

KC-135tanker

CG 68

CG 71

CG 70Kokeesite A

F-16s (2)

F-15s (4)

Jammer

Jammer

Jammer

Jammer

P-3

518 JOH

Results This portion of Mountain Top also met, and in

several cases exceeded, its primary objectives. For ex-ample, it demonstrated the capability of CEC to sup-port the Navy’s silent shooter concept. In addition, twosimultaneous ship engagements with SM-2 using re-mote data were successfully accomplished for the firsttime. The exercise provided an unprecedented oppor-tunity for concept exploration and data collection withfive CEC-equipped units (three of which were Navycruisers) operating with the participation of the Army,Marine Corps, and Air Force elements in a series oflittoral scenarios. It supplied invaluable data for eval-uation of the potential integration of AWACS andthe Marine Corps’ TPS-59 Hawk radar into the CECnetwork.

SUMMARY

Significance of Test ResultsThe Mountain Top ACTD successfully demonstrat-

ed the feasibility of the forward pass mode of targetengagement, an approach conceived over 20 years agoto extend air defense capability beyond a ship’s horizon

Figure 14. Illustrated configuration of Aegis, CEC, aerostat, and Hawk. The Hawk high-powered illuminator/tracking radar was cued forsuccessful engagements from the TPS-59 radar at the elevated Makaha site, as well as from the Aegis cruisers via CEC composite track.Three data paths are shown: blue, Aegis SPY composite CEC track via aerostat relay to cue Hawk fire control; yellow, cue of TPS radarand radar cue of Hawk fire control; red, direct cue of Hawk fire control.

CG 71

CG 68

Target

TPS-59

CEC

Kokee site

CECline

Hawk launchersand fire control/

illuminators

Aerostat relayof CEC data

TPS-59 datafiber-optic line

Makaha Ridge

Hawk/CEC experimentalfire control interface

CEC network

Aegis firm trackof target



Makaha

Composite trackwith TPS-59 and Aegis

SPY-1 contribution

Composite trackfrom TPS-59 data only

CG 71

CG 68

TPS-59

Figure 15. CEC display with TPS-59 radar. A replay of collected TPS-59 radar measure-ments, conditioned to appear in the format of an SPS-48E radar, was run through aCooperative Engagement Processor along with data collected simultaneously from CECunits. The lower track indicates that the TPS-59 had detected a target not detected by thecruisers. The track emerging and then turning toward the island is a target drone. The TPS-59 was in a position to detect the outbound target before the Cape St. George (CG 71) coulddo so. Had it been networked with the CEC, CG 71 could have provided data for thecruiser’s SPY-1B to acquire the drone prior to its own autonomous detection.

with the aid of surveillance and target illumination airvehicles.7 In his message of congratulations, the lateChief of Naval Operations ADM Mike Boorda wrote

‘Outstanding’ is the only word to describe the re-sounding success you all achieved in both the advancedconcept technology demonstration (ACTD) and en-hanced phases of the recently completed Mountain Topdemonstrations. In discussing emerging technologiesand warfighting capabilities, ‘revolutionary’ may be oneof the most overused words in Washington. In this case,however, there is no question that you have set the stagefor a revolutionary new way of fighting in the air defensearena. Because of your dedication and hard work, ourtask of quickly deploying this unprecedented warfightingcapability has been made much easier. You were on time,on target, and on the money. Congratulations on a majorsuccess. All the best.8

The evolution of the concept and the ability of ex-isting Navy systems to be modified for such a demonstra-tion were the result of convergent mutual developmentof these systems, with APL as a key player. The fact thatCEC, conceived by APL, was designed to enable suchforms of cooperative engagement is due to the Labora-tory’s capability to preserve the technical vision overmultiple generations. It may also be attributed to APL’scomplementary roles in development of Navy air defensesystems that enable it, in partnership with the Navy, to

intense. The defis being vigorourecommending rthis writing, a suing Set 1 in scalto lead to a depThe various airberation include aForce aircraft, anunmanned aeriahanced performaForce missile vaCEC and JTIDSsensor/weapons work, respective

The EnhanceFirst, they contrially directed IOCtion having beenMarine Corps hasystem, and the prototype integraircraft and missvices are further for CMD as well in a joint netwo


ensure that key synergistic featuresare present in these systems to facil-itate their technical advance in abalanced, focused, and mutually sup-porting manner.

The potential of the land-attackCMD concept to protect U.S. andcoalition forces in future conflicts isa compelling reason for further de-velopment of such capabilities bythe joint services. The success ofthe Mountain Top exercises pro-vided a critical step toward this ob-jective by proving the integrationconcept and the potential perfor-mance amplification over individ-ual systems. These tests also furtherexplored the foundations of weap-on and sensor networking (viaCEC) and command/control net-working (via JTIDS) for joint-ser-vices CMD operations.

The FutureSince the Mountain Top be-

yond-the-horizon firing eventswere successfully completed, dis-cussions of a follow-on have been

inition of the follow-on CMD phasesly pursued by DoD, with all servicesoles and next-phase approaches. As ofbstantial test operation, even exceed-e, is being discussed, with the intentloyable prototype national resource.orne platform options under consid- very large Army aerostat, a large Aird a Navy carrier aircraft, possibly withl vehicles in a CEC subnet for en-nce. Advanced Army, Navy, and Airriants are also being considered, and are expected to be integrated as thenetwork and command/control net-ly.d Scenarios also have made an impact.buted to CEC meeting its congression- schedule, with significant risk reduc- part of those scenarios. Second, the

s begun integrating CEC into its HawkAir Force and Army are considering

ations of CEC into the AWACS testile batteries, respectively. All the ser-examining the use of CEC and JTIDSas tactical ballistic missile defense rolesrking study.

1997) 519


REFERENCES1“The Cooperative Engagement Capability,” Johns Hopkins APL Tech. Dig.16(4), 377–396 (1995).

2Cruise Missile Defense Advanced Concept Technology Demonstration Phase I,Office of Naval Research (Mountain Top) ACTD Management Plan (Aug1994).

3Dockery, G. D., and Konstanzer, G. C., “Recent Advances in Prediction ofTropospheric Propagation Using the Parabolic Equation,” Johns Hopkins APLTech. Dig. 8(4), 404–412 (1987).

4Rowland, J. R., and Babin, S. M., “Fine-Scale Measurements of MicrowaveRefractivity Profiles with Helicopter and Low-Cost Rocket Probes,” JohnsHopkins APL Tech. Dig. 8(4), 413–417 (1987).

5Marcotte, F. J., and Hanson, J. M., “An Airborne Captive Seeker with Real-Time Analysis Capability,” Johns Hopkins APL Tech. Dig. 18(3), 422–431(1997).

520 JOH

6Moore, D., 1996 National Fire Control Symposium, Eglin Air Force Base (Jul–Aug 1996).

7Blazar, E., “Firing Blind, Not Blindly,” Navy Times (29 Jan 1996).8Boorda, M., “SUBJ/BRAVO ZULU//” Navy Message from CNO, N03210,

MSGID/GENADMIN/CNO(N86)//Washington, DC (23 Mar 1996).

ACKNOWLEDGMENTS: The authors wish to thank Alexander Kossiakoff,APL Director Emeritus, for his valued editorial guidance in preparing this manu-script. We also gratefully acknowledge the leadership provided by the MountainTop ACTD and CEC program manager, Michael J. O’Driscoll, whose insight,team-building, issues resolution capabilities, and adherence to the systems engi-neering process were critical in making Mountain Top an unqualified success.

THE AUTHORS

JERRY A. KRILL received his B.S. and M.S. degrees from Michigan StateUniversity in 1973 and 1974, respectively, and a Ph.D. from the University ofMaryland in 1978, all in electrical engineering. In 1973 he joined theLaboratory, where he is presently Supervisor of the Sensor and Weapon ControlEngineering Branch of the Air Defense Systems Department. He is also alecturer for The Johns Hopkins University Part-Time Graduate Program.Originally specializing in electromagnetic theory, Dr. Krill has published articleson electromagnetic scattering and guided wave technology and holds a numberof U.S. patents. He has led systems engineering and critical experiments for theNavy’s Aegis and Battle Group Anti-Air Warfare Coordination programs. For 10years he served as the APL System Engineer for the Cooperative EngagementCapability. Dr. Krill was recently named APL’s lead System Concept Engineerfor the Navy Program Executive Office for Theater Air Defense. His e-mailaddress is [email protected].

WILLIAM H. ZINGER is a member of APL’s Principal Professional Staff andAssociate Head of the Air Defense Systems Department. He obtained a B.S.E.E.from the University of Pennsylvania in 1961. Since joining APL in 1962, Mr.Zinger has worked on the design and testing of Fleet radars and relatedelectronics. He has been associated with Aegis and its AN/SPY-1 radar sinceprogram inception. More recently, he served as the Technical Director of APL’sCooperative Engagement Capability effort and led the Ship Self-Defense Systemeffort within his organization. His e-mail address is [email protected].


mountain top: beyond-the-horizon cruise missile defense

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