standard missile: a cornerstone of navy theater air missile defense

234 JOHNSHOPKINSAPLTECHNICALDIGEST,VOLUME22,NUMBER3(2001)

M. MONTOYA

S

StandardMissile:ACornerstoneofNavyTheaterAirMissileDefense

Matthew Montoya

tandardMissile is theprimaryNavyFleetanti-airmissile system. Itshistory stemsfromrequirementsestablishedbytheNavyin1945,andithasevolvedcontinuouslyasdrivenbycontinualchangesinthethreatandoperatingconditionsofournavalforces.Overtheyears, theneedforanadvancedweaponcapabilityhas ledto intensesystemseffortsinvolvinguniversities,governmentlaboratories,andindustry.Thisarticleexam-inesthehistory,majordevelopmentefforts,andfutureofStandardMissile.

INTRODUCTIONIn 1965, the Advanced Surface Missile Systems

(ASMS)AssessmentGroupissuedareport(TheWith-ingtonStudy)statingthattheNavyneededanewmis-silesystemtoaddressthefuturethreat.However, lim-ited by budgetary considerations, the Navy, as it haddonepreviously,consideredupgradestoStandardMis-sile (SM)toachieve its requirements.Theseupgradesapplied to both SM predecessor systems, Terrier andTartar,aswellastotheemergingsystem,Aegis.Thus,with SM viewed as the primary Anti-Air Warfare(AAW)weaponfortheAegisWeaponSystem,signifi-cant enhancements have been made to major missileelements, including propulsion, guidance, and fuzing.ThisclosecoordinationofmissileandshipsystemshasbeenabsolutelycriticalfortheNavy.

The operational use of any guided missile requiresdirectsupportfromacombatsystem,whetheritisfiredfromland,sea,orair.InthesurfaceNavy,manymissilesystemrequirementsareunique,notonlybecauseofthesea environment,which is incrediblyharsh, butmore

significantly because the supporting systems are com-batantshipswithvariedmissionsandtacticalrequire-ments. Therefore missile weapon system designs areundersevereconstraintsintermsofphysicalsize,weight,andshipboardlocation.Additionally,themissilesystemmustbetotallyconsolidatedwithintheshipcommandstructure, which encompasses all weapons aboard theship.Becauseof this closeweapon-to-ship integrationrequirement, it is technically and economically prac-ticaltoupgradethemissilesystem’sperformance,pro-videdthatforethoughtgoesintotheplanningandspe-cialdesignconceptsareincorporated.

ThedevelopmentofSMhas followed these systemsengineeringprinciplesthroughoutitshistory.Thatis,nec-essaryincrementalmissileupgradeshavebeenmadebasedon long-term system requirements in which improve-mentsaremadebybuildingsolidlyonexistingresourcesand knowledge (Fig. 1). Each module is designed witha tolerance to change so that missile upgrades have aminimum impact on other ship elements and support

JOHNSHOPKINSAPLTECHNICALDIGEST,VOLUME22,NUMBER3(2001) 235

SM: CORNERSTONE OF THEATER AIR MISSILE DEFENSE

activities.Inaword,SMisbasedoncommonality:com-monalityofcriticalcomponentswithinthemissilefromonegenerationtothenext;commonalityamongversionsfiredfromTerrier,Tartar,andAegisships;commonalityof interfaces with supporting radar and launching sys-tems;andcommonalityinengineeringexpertise,techni-caldata,andlogisticsupport.

Thus,astheNavylookstothefuture,SMisviewedas the point of departure for many developmentalefforts. Production and in-service efforts for SM-2BlockIIIA,BlockIIIB,andBlockIVprovidetheback-boneforcurrentFleetcapability.However,engineer-ing,manufacturing,anddevelopmenteffortsforSM-2BlockIVAforAreaBallisticMissileDefense(BMD)requirements, SM-3 for Navy Theater Wide require-ments,andSM-4(LandAttackStandardMissile)forNaval Surface Fire Support requirements provide forthe Navy’s near-term and future multimission needs.Finally,lookingatfutureadvancedthreatsandenviron-ments,tradestudiesarecurrentlybeinginitiated,underthe direction of the SM Program Office, PEO(TSC)PMS422,toaddresstheNavy’smultimissionrequire-ments with upgrades to variants of SM-2 MediumRange(MR),SM-2ExtendedRange(ER),SM-3,and

SM-4.AsystemsapproachwillcontinuetobeusedasithasbeenforSMsincepost–WorldWarIItoaccom-plishthesegoals.

ORIGINS OF STANDARD MISSILEIn1944,aglaringdeficiencyinNavyAAWdefenses

was clearly exposed during the Battle for Leyte Gulf:On 19 October at 0740, the escort carrier USS Santeebecamethefirstvictimofakamikazeattack.Theorigi-nalkamikazeswereJapanesefighteraircraftarmedwith500-lb bombs. Continued attacks, although counteredbyconcertedanti-aircraftfire,weredevastating,particu-larlyatIwoJimaandOkinawa.BeforethewarendedinAugust1945,suchattacksonU.S.shipsresultedinabout15,000 casualties. Proximity fuzed anti-air gunfire (Fig.2),1complementedbyNavyfighteraircraft,wasunabletoeffectivelycopewiththekamikazeattackconcept.

The Navy recognized immediately that a weaponsystemwithveryquickreaction,veryhighspeed,andlong enough range to engage an attacker prior toweaponreleasewasvitallyneeded.Accordingly,inJan-uary1945,theNavyBureauofOrdnancedirectedAPLasfollows:

Figure 1. The evolution of in-service Standard Missiles.

1945 Bumblebee Program

1949 Tactical prototype

1953 Terrier in Fleet

1956 Tartar development

1960 Tartar in Fleet

1962 Homing Terrier in Fleet

1968 SM-1 in Fleet

1971 SM-1 Blk V

1976 First SM-2 Blk I flight

1980 SM-2 Blk I testing at sea

1982 SM-2 Blk II testing at sea

1982 SM-2 Blk III testing at sea

1991 SM-2 Blk IIIA testing at sea

1994 SM-2 Blk IIIB/IV testing at sea

Beamriding wing control

Tail controlHoming guidance

SM-1: Solid-state circuitry

SM-1 Blk V: Countermeasures improvements

SM-2 Blk I: Midcourse Guidance

SM-2 Blk II: High-impulse motors Blast-frag warhead FFT signal processing

SM-2 Blk III/IIIA: Low-altitude improvements More lethal ordnance

SM-2 Blk IIIB: Dual-mode guidance

SM-2 Blk IV: Booster Linear steering control Improved electronic counter-countermeasures Improved aerodynamics

Monopulse seeker


M. MONTOYA

Acomprehensiveresearchanddevelopmentprogramshallbeundertaken,embracingalltechnicalactivitiesnecessarytothedevelopmentofoneormoretypesofrocket-launched,jet-propelled, guided, and anti-aircraft missiles. This pro-gramshallincludepertinentbasicresearch,investigations,and experiments, and the design, fabrication, and testingofsuchmissiles,theircomponentparts,andsupplementaryequipment.2

Thuswasestablishedthe“Bumblebee”Program.Thescopeoftheprogramwasvast.Neverbeforehad

such a weapon system been developed. There was notechnologicalbasefordesigningamissilewiththenec-essarycharacteristics:long-rangeguidedflightatsuper-sonicspeeds.Thisambitiousgoalrequiredthatseveraldifferenttechnologiesbeexploredandthatasufficientbodyofnewknowledgebeacquiredtoformarationalbasisforengineeringdesign.Thegreatestadvanceswererequiredinthefieldsofjetpropulsion,supersonicaero-dynamicsandcontrol,andmissileguidance,all infanttechnologies.

Toanswerthechallengeposedbythelackofscien-tificandengineeringfoundationsfordevelopingguidedmissiles to defend the Fleet, APL applied a teamingapproachthathadprovedsosuccessfulinthedevelop-ment of the VT fuze. The collaborating organizationswere called associate contractors, and their contractsspecifiedthattheirtaskswouldbeunderthetechnicaldirectionofAPL.Asmanyas17university, industry,andgovernmentorganizationswereinvolved.

By1949theBumblebeeProgram(Fig.3)hadestab-lishedthefeasibilityofproducingatacticalship-to-airanti-aircraft guided missile. A supersonic test vehicleusingsolid-fuelboosterandsustainerrocketmotorswasused to test and evaluate the radar-beam–controlledguidance and control system for the planned opera-tionalTalosguidedmissile.Thefirst roundwasdeliv-eredon31January1950andflight-testedattheNavalOrdnanceTestStation,ChinaLake,California,on16February1950.Thistacticalprototypesuccessfullydem-onstratedbeamridingguidanceagainstdronetargets.3

Aversionofthetestvehicleperformedsowellthatthe Navy decided to develop it for use as an AAWweaponinwarshipssmallerthanthosedeployingTalos.Thus,theTerrierMissileSystemcameintobeing.TheTerrierProgramproceededrapidly.InNovember1955,theUSSBoston(CAG1)wasrecommissioned(Fig.4),and,carryingTerrierMissiles,becamethefirstguided-missileshipintheworld.Theeventmarkedtheculmi-nationofthefirstphaseoftheTerrierProgram.

ThefirstsignificantupgradetoTerrierwasthechangeinthecontrolsystemfromwingcontroltotailcontrol.This was prompted by the need for better maneuver-ability to counter evasive tactics on the part of theattacker.4 The second major upgrade was the changefrombeamrider guidance to semi-activehomingguid-ance,achangethatwasmadeincoordinationwiththedevelopmentofasmall-shipmissilebasedontheTerrier

Figure 2. The VT fuze.

CobraTalos 6B

(beamrider with terminal homing)

19551946

Talos 6C1RTV

19471959

Talos XPM

1949

STV-3 1951 1958

Terrier I(beamrider)

Terrier II (BT)(beamrider)

1948STV-4

1954Terrier II (HT)

(homer)

1960

STV-2

1957

CTV

1946

TARTAR(homer)

1959

StandardMissile,

extended range(homer)

StandardMissile,

medium range(homer)

1966

Ramjetpropulsion

Steeringand

control

Testvehicles

Tacticalmissiles

Figure 3. The Bumblebee Program.



aerodynamicconfigurationandcontrolsystemdesign.5Forthesmallermissile,designatedTartar,adual-thrustrocketmotor(DTRM)wasdevelopedtoprovidehighthrust for the initial (boost) phase of flight, followedbymuchlowerthrustforthesustainphase.TheNavyestablishedashipbuildingprogramthatresultedintheUSSCharles F. Adams(DDG2)classdestroyer(Fig.5),which,armedwithTartar,wasfirstdeployedin1960.

IntheyearssincetheBumblebeeProgram,themissilehasevolvedthroughmanygenerationsandupgrades.Asthethreathaschangedandintensified,counteringmod-ificationshavebeenidentifiedandappliedtothemissiledesign—alwaysstayingabreastofprudentapplicationsofnewtechnology.

EVOLUTION

SM-2 Development/SM-1 UpgradeIn the early 1960s, the technological advances of

solid-state electronics had matured sufficiently to jus-tifytheredesignofboththeTerrierandTartarmissiles.TerrierbecameSM-1ERandTartarSM-1MR.Withtheuseofmodularconstructionandatailcontrolcon-figuration that is not sensitive to change in dimen-sionalandweightcharacteristics,performanceimprove-mentsbyblockchanges(acollectionofrelateddesignchangesintroducedduringproduction)werepossible.6

BlockchangeshaveledtoaprogressivefamilyofSMs.SM-1ERwasatwo-stageconfigurationhavingasinglethrust booster that separated from the missile a fewsecondsafterlaunch.Therocketsustainerthenignitedfor the remainder of flight. SM-1 MR employed aDTRMdevelopedearlierforTartar.

In themid-1960s, air threats tonaval forcesbeganundergoinga transition fromaircraft toanti-shipmis-siles.Suchmissileattackswouldlikelyhavebeencoor-dinated with the use of various countermeasures andspecial tactics. It was at this point, as noted earlier,thattheASMSAssessmentGrouprecommendedanewweaponsystemthatwouldcombinehighperformance,shortreactiontime,aninherentcountermeasurescapa-bility,andhighavailability.In1969,theNavyawardedacontractfortheAegisWeaponSystem,whichwoulduseimprovedversionsofSM.Thisversion,designatedSM-2MediumRange(SM-2MR),incorporatedanewinertialguidancesystemandmissile/radardatalink.

SM-2MRperformanceintermsofinterceptrange,altitude, and terminal homing accuracy was greatlyimproved by this upgrade. More importantly, it nowbecame compatible with and could be used by theAegisWeaponSysteminanengagementscenariothatrequired multiple missiles in flight (simultaneously)againstdifferenttargets.

In the early 1970s the Navy sponsored a study todeterminehowthesenewcapabilitiesmightbeusedtoupgradetheperformanceoftheTerrier/Tartarcombatsystems.Aconceptevolvedthatadaptedthenewmissilefeaturesforbothsystems.Tartarusedthemedium-rangemissiledesignedforAegiswithminimalchanges.Ter-rier, incorporating a higher-energy propulsion system,wasdesignatedSM-2ExtendedRange(SM-2ER).

AttheonsetofdevelopmentofSM-2,SM-1BlockV was in production as the primary weapon for FleetAirDefensebyTerrierandTartarships.SM-1employshome-all-the-way guidance with no midcourse guid-ancemode.TheNavyplannedtocontinuetouseSM-1exclusivelyinasubstantialnumberofwarshipsfortheforeseeable future, since it was predicted that, by thetimeSM-2wasreadyforinitialoperationalcapability,manyoftheseshipswouldbeveryclosetotheendoftheirservicelife.Itwasprudent,however,toconsidertheupgradeofSM-1withapplicablefeaturesdevelopedwithintheframeworkoftheSM-2Program.AnSM-1BlockVIupgradeprogramwasthereforeestablishedinthelate1970swithobjectivesidentifiedasfollows:

• Incorporate the SM-1 monopulse receiver (SM-2BlockIcommonality)

• IncorporatetheMk45Mod4targetdetectingdevice(TDD)(SM-2BlockIcommonality)

• ProvideSM-1BlockVIguidanceandordnancesec-tions as alternate and interchangeable with SM-1BlockVsections

Figure 4. USS Boston (CAG 1).

Figure 5. USS Charles F. Adams (DDG 2).


M. MONTOYA

• Provide production commonality between SM-1BlockVIandSM-2BlockI

• EstablishproductioninFY1980

The listed attributes were incorporated in SM-1BlockVIproduction.Inthemeantime,SM-2BlockIIdevelopmentwasproceeding.Theprincipal threat forSM-2wasidentifiedasfast,high-flying,anti-shipcruisemissiles.Analysis,supportedbyflighttestingofSM-2,concludedthatanupgradetotheTDD,i.e.,theprox-imity fuze, was needed to maximize missile kill per-formance against these targets. This resulted in theTDDMk45Mod5.Stillstrivingtomaintainproduc-tioncommonalitybetweenSM-2andSM-1,theNavyupgraded the SM-1 TDD from Mod 4 to Mod 6 andreplacedthecontinuousrodwarheadwiththeMk115blast/fragwarheademployedbytheSM-2.SM-1socon-figuredwasdenotedSM-1BlockVIA.

This process of SM-2 development followed bySM-1 upgrade to achieve comparable performancecontinueduntilthelate1980s.Finally,theLowAlti-tude Program for SM-2 Block III led to SM-1 BlockVIB.However,inoneverysignificantdeviationfromthis development process, a missile receiver upgradeto eliminate susceptibility to a phenomenon knownasclutter-derivednoisewasfirstincorporatedinSM-1BlockVIBand subsequently inSM-2Block III/IIIA.Thismissileupgradeisparticularlysignificantsinceitresulted ineffectivemissileperformanceinadomainthat is viewed as the principal hostile environmentwithinwhichtheNavyisexpectedtooperate intheforeseeablefuture(Fig.6).SM-1continuesinserviceinanumberofNavywarshipsworldwide,includingtheFFG7classcombatsystems.

SM-2 Medium Range

Blocks I and IIForSM-2BlockI,thefirstmissileintheSM-2family,

bothMRandERversionsweretestedatseafrom1976through1979.TheChiefofNavalOperationsapprovedSM-2BlockIER,afterasuccessfulflighttestprogramofftheUSSMahan,forservicein1979.

For SM-2 Block II, during the late 1970s to early1980s, the perceived AAW threats to the Navy werethefast,high-flying,anti-shipmissilessuchastheAS-4andAS-6supportedbyheavystandoffelectroniccoun-termeasures. Operations analysis concluded that thethreatcouldbesuccessfullycounteredbyupgradingSMpropulsionandreceiversignalprocessing.Accordingly,as stated earlier, the Navy had established programstodo just that forboththeSMERandMRversions.This resulted in a greatly increased impulse DTRM,Mk 104, for the SM-2 MR version. With this, SM-2MR’s approval for service occurred subsequent to thecommissioningofthefirstAegiswarship,USSTicond-eroga(CG47),in1983.ForSM-2BlockIIER(Terrier),agreatlyincreasedimpulseboosterrocket,Mk70,wasadded.TheSM-2ER(Terrier)missile systemwasputintoserviceduringthe1980saswell.

ForboththeSM-2BlockIIMRandER,themissilefrontradio-frequency(RF)receiverswereupgradedbytheincorporationofadigital-designfastFouriertrans-formsignalprocessoremployingoff-axislogictodetectthepresenceofstandoffjammers.FlighttestingatWhiteSandsMissileRangeandatseaverifiedtheeffectivenessofthemissileupgrades.

Blocks III, IIIA, and IIIBAs the threat evolved, and with the high-altitude

domain effectively countered, it was time to focus onthelow-flyinganti-shipmissilesproliferatingthroughouttheworld.Asbefore,afterdetailedanalysisandexper-imentation, it was concluded that an upgrade to SMwastheanswer.ThemissilethatemergedwasdenotedSM-2BlockIII.

TheSM-2low-altitudeimprovementprogramincludedthree basic goals: (1) diminish the effects of target RFenergyreflectionfromtheseasurface,(2)derivemissilealtitude for low-altitude engagements, and (3) permitidentificationoflow/slowtargets.Thismissilesystemwassuccessfullydemonstratedduringthelate1980sandsub-sequentlyfielded.

TherewasafurtherevolutionoftheBlockIIImis-sile,BlockIIIA.ThiswasdistinguishedbyanupgradetothewarheadandTDDsections.Thismissilesystemordnance upgrade was successfully demonstrated andfieldedintheearly1990s.

The latest evolution of SM-2 MR is SM-2 BlockIIIB.ThisSMisequippedwithadual-modeRForinfra-red(IR)homingseekercapability.SM-2BlockIIIBwassuccessfullydevelopedandoperationallytestedin1994andbecameoperational in1997.ItservesasthebasisfortheAegislow-altitudecapability.

SM-2 Extended RangeThecoordinationofallavailablebattlegroupresources

inprosecutingtheengagementofanattackingforcehas

Clutter-derivednoise

Clutter-derivednoise eliminated

SM-1 Block VIA SM-1 Block VIB

Figure 6. Clutter-derived noise comparison.



alwaysbeenanunderlyingpreceptofNavybattledoc-trine.TheemergenceoftheAegisWeaponSystemandits AN/SPY-1 radar provided a major element in theimplementationofthatprecept.UsingtheAegissystemas a baseline, the Navy has progressively designed anddevelopedcompanionsystemelementsforincorporationinto warships over the past 20 years. For example, theCooperative Engagement Capability (CEC), based ontheMountainTopProgram7todemonstratethefeasibil-ityofabeyond-the-horizoncapability,aswellasrecentlysuccessfullycompletedtechnicalandoperationalevalu-ations, isworking toward becoming a reality. Fornow,though,withinCEC,theconceptofasurface-launched,air-supported engagement of cruise missiles has beenvalidated and has provided the impetus for follow-onJoint services pursuit of an extended, beyond-the-hori-zonengagementcapabilityfordefenseoflandsitesfromland-,air-,andsea-basedmissiledefensesystems.

AdominantattributeofCECis thecapabilityofamissile-firingwarshiptoengagetargetsthatareoveritsradarhorizonbutwithintheviewofaforward-locatedcompanionwarship,whichcanprovideappropriatefirecontrolsolutionsviatheCEClinktotheshooter.Theforward-locatedship,atanappropriatetime,canassumecontrolof thefiredmissile for the terminalportionofthe engagement. However, the AAW missile in theAegisFleetinthemid-1980swasSM-2BlockII,pow-eredbytheMk104DTRM.Sinceitlackedtheneces-saryextendedengagementrange,ahigher-impulsepro-pulsionsystemwasneeded.

The groundwork had been laid for the requiredimprovement to SM-2 beginning with the fifth Aegiscruiser,USSBunker Hill(CG52),inwhichtheMk26LaunchingSystemwasreplacedbytheMk41Vertical

electronic countermeasures resistance was also rein-forced.Withthehigherspeedsachieved,greatermaneu-verabilitywas realized aswell as longer-range engage-ments.TheBlockIVmissilewassuccessfullytestedatWhite Sands in the early 1990s and at sea in 1994.It is now in low-rate initial production and serves asthebaseline for the family ofSMs that support BMDand futureTheaterAirandMissileDefense(TAMD)needs.

Ballistic Missile Defense

Endo-atmospheric interceptsAgain,pushedbytheever-changingthreatasdem-

onstrated in Desert Storm and thereafter, the tacticalballisticmissilebecamethedominantthreat.Asbefore,throughanalysisandexperimentation,itwasconcludedthatanevolvedSM-2BlockIV,denotedSM-2BlockIVA,wouldprovideprotectionagainstthatthreat.ThedesignofSM-2BlockIVA,becauseofthethreatchar-acteristicsandpayload,wouldneedtobeequippedwithdual-modeguidance,RFandIR,aswasdoneintheIIIBprogram.

However,thedemandinginterceptaccuracyrequire-ments for SM-2 Block IVA dictated an entirelydifferent missile IR system design. To address endo-atmosphericintercepts,anewseekerheadwithhighlyaccurate rate integratinggyroswasdesigned tobeputon an SM-2 Block IV airframe. An inertial referenceunitincorporatingaringlasergyrowasdesignedfortheguidancesection,theautopilotwasredesignedsothatthe missile could capitalize on the inherently higher“g”capabilityoftheBlockIVAairframe,andaforwardlooking fuze (FLF) was developed to address stressing

LaunchingSystem.ThesizeoftheMk26strictlylimitedthemissile’sexternalconfigurationanddimen-sions to expand, whereas the Mk41systemdidallowforanincreaseinthesizeofthepropulsionsystemneededforSM-2ER.Accordingly,theNavyestablishedaprogramtodesign and develop SM-2 BlockIV(Fig.7). Itsmajorupgradewasthe incorporation of a new thrustvector–controlledbooster, theMk72, which was mechanically andelectricallyintegratedwiththepro-pulsion system, the Mk 104, usedon SM-2 Blocks II/III/IIIA/IIIB,which are now in the Fleet. Inadditiontothepropulsionupgrade,BlockIVwasequippedwithanewdigital autopilot, a digitally con-trolled seeker head, and severalguidance section improvements; Figure 7. SM-2 Block IV.

Slip-cast fused silica radome •Increased RF bandwidth •Increased resistance to heatTelemeter

New booster •Increased kinematics •Thrust vector control •Vertical Launching System compatibility

Redesigned steering control •Digital autopilot •Linear actuators •Insulated control fins

Modified dorsals •Increased maneuverability •Improved stability

Warhead section •Common to Blk IIIA/IIIB

New guidance section/radome


M. MONTOYA

BMD endgame conditions. A successful SM-2 BlockIVARiskReductionFlightDemonstration in January1997, which had a representative flight configurationofthecurrentSM-2BlockIVA,hadallowedthispro-gramtocontinue.ResultswerepromotedatthehighestlevelsandwerefeaturedonthecoverofAviation Week.Thus,theNavygainedconfidenceenoughtoauthorizethe initiationofengineering,manufacture,anddevel-opmentfortheSM-2BlockIVAProgramin1997.

Currently, two successful flight tests of control testvehicleshavebeenaccomplishedundertheSM-2BlockIVAProgram.Theoutcomeoftheseflightshasallowedtheprogramtocontinuewithguidedtestvehicles,whichareexpectedtobeflownduring2001and2002,withamissileinitialoperationalcapabilityof2003–2004.

Exo-atmospheric interceptsTo address exo-atmospheric intercepts during the

earlystagesofBMD,requirementsformulationanddem-onstrationprojectsforaflighttestprogram,denotedtheTerrierLightweightExo-atmosphericProjectile(LEAP),wereimplemented(Fig.8).Itsgoalwastodemonstratebyexperimentthevalidityoftheanalyticconclusionsoftheachievablekilleffectivenessofkineticwarheads(KWs)mountedonSMTerrier(ER)airframesfiredtoachieve interceptsof tacticalballisticmissile–like tar-getsattheirrelatedaltitudes.Twoflightintercepttestsin 1994 and 1995, although yielding less than sensa-tionalresults,gaveconfidencethattheprogramwasontherightcourseandshouldbecontinued.ThecurrentLEAPconcept,designatedSM-3andbasedonanAegislaunchandsupportsystem,hasafour-stageapproachtoachievetherequiredintercept(justasTerrierLEAP):

1. Mk72boosterrocketmotor2. Mk104DTRM3. Third-stage rocket motor (TSRM) and avionics

package4. KWandavionicspackage

Eachstageissupportedbyanassociatedcontrolsystemto permit maneuvering during flight. The function ofthefirstthreestagesistodelivertheKWtoapointinspacefromwhichitcanacquire,track,anduseitsownpropulsion system to divert its own course to achieveaninterceptofthetargetthreat.TheSM-3operationalconceptisdepictedinFig.9.Sincetheflightsequenceof SM-3 differs dramatically from that of traditionalSMs,weprovidethefollowinghigh-leveldescription.

First stage (boost). Themissileisfiredwithalaunchbearingandelevationanglerelativetothelocallevel.Itisfiredverticallyandpitchesovertoalignitsvelocityvectorwiththeinitializedcommands.AN/SPY-1radaracquiresandtrackstheAegismissilebeaconduringthisphase.TheMk72booster separatesat thedesignatedtimeandconditions.

Second stage (endo-midcourse). TheAegisWeaponSystem, via the Aegis RF uplink, transmits accelera-tioncommandstoSM-3.Themidcourseguidancelaw,aheadinganglecontrollaw,alignsthemissilevelocityvector with the reference vector pointing at the pre-dicted missile/target intercept point. The GPS is anintegralelementoftheSM-3guidancesystem.Thesec-ond-stage Mk 104 DTRM separates from the missileassemblyatburnout.

Third stage (exo-midcourse). TheTSRMhasatwo-pulserocketmotor.Duringthisphase,theuplinkmes-sage provides new information, which includes targetstatevectordata(positionandvelocity)fromtheAegisWeaponSystem, that ismergedwithGPS-basedmis-sile-developed guidance.The third stageuses burnoutreference guidance, calculatedon themissile, to steerduring TSRM burn. Missile and target positions atTSRMburnoutarepredicted,and steeringcommandstoplacethetwoonacollisioncourseareusedbytheTSRM.Themissile is thrustvector–controlledduringbothTSRMpulseburns.Attheappropriatetime-to-goto intercept, the KW is initialized by the TSRM andreleased.

Fourth stage. Thefourthstage,theKW,isessentiallya missile within a missile. It evolved from the TerrierLEAP kinetic kill vehicle technology and comprisesfourmajorassemblies:(1)acryogenicallycooled,staringlong-wave IR seeker; (2) a guidance assembly whichincludes both signal and data processors, an inertialmeasurement unit, a thermal battery, and a telemetry

Figure 8. Terrier LEAP.



transmitter system; (3) a Solid Divert and AttitudeControl System (SDACS) propulsion assembly; and(4)aninterfaceandejectormechanism,whichprovidesbothmechanicalandelectricalinterfaceswiththethirdstage as well as separation of the KW from the thirdstageintheexo-atmosphericendgameenvironment.Theinterstage assembly remains with the third stage uponejection.

After the KW is ejected from the third stage, theSDACS is ignited and the KW points along the pre-dictedlineofsighttothetarget.TheKWthenacquiresandtracksthetarget.TheKWhasanadequatefieldofviewtodetectthetargetfromitsinitialpointinginfor-mationprovidedathandoverandisdesignedforappro-priatehomingtimes.OncetheKWhasacquiredandistrackingthetarget, itusesapredicted impactguidancelawforaninterceptsolution,ignitesthedivertgrainoftheSDACS,andbeginshomingmaneuvers.Theinter-ceptrequirementfortheKWistoimpactthetargetbodyanddestroyitusingkineticenergy.

BMDanalysisandinitialtestingtodatewithSM-2Block IVA and SM-3 indicate that Aegis employingthese two weapons will provide an effective, credibledefense against tactical ballistic missile attacks, andtogether will permit the Navy to achieve Area andNavyTheaterWidecapabilities(Fig.10).

Naval Surface Fire Support and TargetsInmid-1992, theNavypublished twoMissionNeed

StatementsaddressingNavalSurfaceFireSupport(NSFS)and Supersonic Sea-Skimming Targets (SSSTs). Theformer states that, “There is need for a combinationofguns, rockets, and missiles with sufficient range, accu-racy,andlethalitytomeetthewiderangeofrequirementsin support of amphibious operations and the joint landbattle.”Thelatterstatesthat,“Thereisaneedtorepli-catethesupersonic,sea-skimminganti-shipcruisemissilethreatinordertotestandevaluatecertainNavyweaponsystemsandtoproviderealistictrainingtotheFleet.”

Inresponsetothesestatements, theNavyinitiatedtwoprogramsknownasLASMandLASM-Targetswithgoalstofield,respectively,alow-cost,near-termLASMforNSFSandalow-costSSSTandTerrierMissileTar-gets(TMTs)forFleettraining.Amajorpolicywithinthesetwoprogramsistomaximizetheuseofcommoncomponents,software,andnondevelopmentitemsfrominventoried Terrier/Tartar SM-2 Block II/III, SM-3LEAP,andERguidedmunitionstoreducedevelopmentandproductioncostsandschedules.

LASM (SM-4)Asaresultofananalysisofalternativesduring1999

for thenear-term, low-cost solution forNSFS,LASM

Figure 9. SM-3 concept of operations.

Second stage

Boost (acquire)

En

do

-mid

cou

rse

ph

ase

Third stage,first burn

Exo

-mid

cou

rse

ph

ase

Noseconeejection

Third stage,second burn

Seekercalibration

KW ejection

Acquire, track, divert

SM-3 launch

GPS hot start(varies withscenario)

Schedule

Engage

Target burnout

Detect

Pacific MissileRange Facility

SM-3 launchship

Term

inal

ph

ase


M. MONTOYA

requirements.TheLASMtacticalemploymentconceptisdepictedinFig.12.

The viability of the LASM concept was stronglyreinforced by the successful LASM-1 flight test inNovember 1997. All test objectives were achieved,including the use of GPS for guidance, with actualflight performance matching a six-degree-of-freedomsimulation within 1.0% of nominal. Following thissuccessful demonstration, two other flight tests wereperformedthatshowedtheabilityofLASMtosuccess-fully achieve an approximately 90° dive angle, withproper warhead action. Finally, warhead arena testswere performed to successfully demonstrate LASM’sproposedendgameperformance.ThepositiveoutcomeoftheseeventsallowedLASMtocontinue.

remaining4aretheautopilotbattery(amodifiedSM-2section),guidance(anevolvedSM-3section),targetscommondestruct,andpayload,theonlysectionuniquetoSSST.

The SSST-Targets Demomonstration Program hasfiveobjectives,i.e.,todemonstrate(1)raillaunchfromaland-basedMk5launcher,(2)missileguidancesysteminitialization,(3)in-flightstability,(4)requiredveloc-ityatspecifiedrange,and(5)fire-and-forgetcapability.At thiswriting, theNavyhasnotplanned toprocureSMSSSTs.

TMT. Because of the emphasis on BMD and theneedforalternativetargetrepresentatives,theSMTMThasbeendevelopedandusedduringanumberofimpor-tant BMD exercises. The configuration of TMT is a

Figure 10. Navy Area and Navy Theater Wide coverage.

Ordnancesection

Control surfaces

Dorsal fins

Autopilot / batterysection

Steering controlsection

Mk 104, Mod 2rocket motor

Guidancesection

Shroud /frag. pack

FTSantenna

GPSantenna

Mk 125, Mod 2warhead

FTSpackage

Avionicsassembly

Figure 11. Land Attack Standard Missile (SM-4).

The success of the retrofit andflight testofLASMroundsduring2002 is expected to result inapprovalforlow-rateinitialproduc-tionandfollow-onfull-rateproduc-tion. Initial operational capabilityisexpectedin2003–2004.

LASM-TargetsWithin this program two mis-

sion-specific configurations wereunderconsideration:(1)SSSTand(2)TMT.

SSST. Considering the possi-ble SSST demonstration configu-rationfirst,of10missile sections,6 are handovers from SM-2; the

waschosentosupportNavyneeds.Because of cost, schedule, andperformancerequirements,thecon-figuration for LASM is not com-pletely new, but rather a conver-sion of existing assets. With this,theplannedLASM(Fig.11)con-tains seven missile section assem-blies,sixofwhicharefromSMMR:the steering control section, Mk104DTRM,dorsalfins,autopilot/battery section, Mk 125 warhead,andnoseconeshroud.

The“guidance”sectionwillbeamajorevolutiontoSMMR.ItcanbecharacterizedbyremovaloftheRF seeker and associated AAWprocessor and flight software, andthe addition of the GPS-AidedInertialNavigationSystemsimilarto those used in early LEAP andSM-3 flight tests, LASM-uniquecontrol software, and a height-of-burst sensor to support NSFS

Maximumintercept

altitudeMission

engagement Engagement battlespace

Minimumintercept

altitude

Cross-rangereach

Alongtrajectory

Operatingarea

(SM-3)

Newlaunch Standoff

distance

Launchpoint

Launchpoint

Impactpoint

Impactpoint

Ascentengagement

Newimpact

Defendedarea

(SM-2 Blk IVA)



conversion of Terrier, with only minor modificationsto support its use. To date, the Navy has successfullyusedapproximatelyeightTMTsforBMDtrainingexer-cises.Becauseoftheirlowcost,simpleimplementationprocedures, and ability to replicate representativethreats,TMTswillcontinuetobeusedasaFleet/BMDtrainingtargetastheNavypressestoachievealayeredBMDcapability.

Emerging MissionsWiththeendoftheColdWar,ithasbecomeappar-

ent that the immediateand future threatwillbecon-tained within the littoral environments where mostrealisticscenariosarecharacterizedbylow-flyingcruisemissileattacks(Fig.13).Thisveryhighclutterenviron-ment, as discussed earlier, was addressed for SM withanupgradetothereceiverduringthemid-1990s.Thedevelopment of other AAW system elements to per-formsuccessfullyalsointhisenvironmentwillresultinagreatlyexpandedAAWbattlespace.

Onestartingpointfortherealizationofthisexpandedbattlespace,andanewmissionarea for theNavyand

Figure 12. LASM concept of operations.

SM, is the engagement of low-flying threats by ship-launched missiles beyond the firing ship’s radar hori-zon.Thisconceptwasconsideredovertwodecadesago.Byremovingthelimitationoftheship’sradarhorizon,such a concept envisioned the interception of targetsmuch farther from the defended and engaging units,allowingtimeforadditionalengagements ifnecessary.Theearliestversionof theconceptembodiedtheele-mentofthebeyond-the-horizonguidanceofSM,firedfromanAegisship,byanF-14fighteraircraftmodifiedtoprovidemidcourseandterminalsemi-activehomingguidance, thus allowing the missile to home on thereflectedilluminationfromthetarget.Thisconceptwasknownas“forwardpass.”

Amodifiedformoftheforwardpassconceptemergedinthelate1970s.It featuredaconceptual, long-rangeramjet dual-mode guidance–capable missile fired froman Aegis cruiser and flown by a carrier-based surveil-lanceandfirecontrolaircraft.Theaircraftwouldcarryadvanced, long-range sensors to detect anti-ship mis-siles launchingenemybombersand to takeovermid-course missile control from the ship via an onboard

Midcourse phase •Missile flies near command point •Guidance commands generated within missile •Inertial instrument errors reduced by in-flight GPS updates

Boost phase •Pitch over •Guidance •Missile achieves supersonic speed

Targeting data •Forward observer •UAV •Satellite

Initialization •Initialization and target data supplied •GPS initialization

Warhead initialization phase •Flight path angle control •Ground height-of-burst calculated •Inertial guidance during GPS jamming

Mk 125 warhead

Timeline 30 s

10 s200–500 s Time of flight

On-board mission processing

Missile initialization and launch

VLS ship


M. MONTOYA

Figure 13. Notional littoral engagement scenarios.

aircraft-to-missile link. This concept, resulting fromtheNavy-sponsoredOuterAirBattleStudy,identifiedthe need for a long-range form of SM (now knownasSM-2BlockIV)alongwiththeneedfora“coopera-tiveengagementlink.”TheCECProgramevolvedfromtheworkdescribedearlier,andprovidesavitalelementin the development of an AAW capability to engageenemy,overland,incomingcruisemissiles.

The ability to intercept low-flying threats beyondthe horizon was demonstrated during the MountainTop Advanced Technology Demonstration in 1995and 1996. The system architecture for MountainTop included an experimental airborne search radar(RSTER)andanMk74firecontrolsystemlocatedonamountaininKauaithatenabledthedetection,track,anddevelopmentofafirecontrolsolutionforanincom-ingtargetbeyondtheradarhorizonofanAegiscruiser(Fig. 14). The fire control solution developed by theMk74systemwaspassedtotheAegiscruiser,viaCEC,whichthenlaunchedSM-2.TheSM-2wascontrolledduring midcourse by Aegis command midcourse guid-ance, via uplinks from the Aegis cruiser. The Aegiscruiser developed the midcourse guidance commandsfromtarget trackspassedto it fromtheMk74systemand from its own tracking of the intercepting SM-2.The SM-2 transitioned to terminal homing and wassupported with illumination from the Mk 74 system,notthefiringship,thusallowingtheentireengagementbeyondthefiringship’sradarhorizon.

Tosupportthisevent,SM-2BlockIIIAwaschosen.Ithadalreadyundergonethe receiver redesignupgradenoted earlier and was therefore suitable for use in thepotentialhigh-clutterenvironment(i.e.,forwardscatterand backscatter) in the Mountain Top geometry. The

hope was to be able to use SM-2BlockIV,butithadjustcompletedits operation testing, was preparingforitstransitiontoproduction,andits development configuration didnot directly support the require-mentsofthenewreceiverredesign.

Many risk reduction activitiesweredonebyAPL forSMto sup-porttheMountainTopdemonstra-tion,including:

• Round-level ground-based test-ingintheGuidanceSystemEval-uationLaboratory

• SMsix-degree-of-freedomsimu-lationpreflightpredictionstakinginto account the architecturerequirements, including CEC,Aegis,andSMreceiverredesignfeatures

• CaptiveflighttestswithanSMseekerassemblyandtheMountainTopsystemarchi-tecture and geometry for data verification and riskreduction

As a result of thesevery successful test-firingdem-onstrations, definition of the follow-on DoD CruiseMissileDefenseProgramhasbeenvigorouslypursued,with all services recommending roles and next-phaseapproaches.AdvancedAirForce,Army,andNavyair-borneplatformsandmissilevariantsarebeingconsid-ered with CEC and are expected to be integrated tocreatetherequirednetworkandsystemtoachievetheJointservicesrequirements.

AvariantofSMwillprobablybeusedinfutureOver-land Cruise Missile Defense system architectures. Atthis point, an evolution of SM-2 Block IV, has beenpursuedthatincludesanactiveRFseekersystemwhichfurtherfacilitatesbeyond-the-horizonengagementsowingto the lackof a requirement for an illumination radar.ThelatestSMERwillbefolloweduptoallowtheNavyto expand its capability to meet the emerging threatin the littoral, extended battlespace requirements, andbeyond-the-horizonengagementsneeds.

International SM Development Uptoabout5yearsago,thesalesandworkingenvi-

ronmentofSMhadbeenthepurviewofitsdeveloper,the U.S. Navy, while the role of our internationalpartnershadbeenthatofrecipient.Sincethen,how-ever,theseinternationalpartnershavemadetechno-logicaladvancesinmultifunctionradar(MFR)systems,whichhascreatedtheneedforSMtoadapttointer-operability in three capability areas: (1) terminalhomingrequirementsduetothecreationofinterrupted

E-2C

DDG 51

SM ER

SM ER

Patriot

CG

AFCR

F-15

AMRAAM

AWACS



Figure 14. Mountain Top engagement architecture.

continuous-wave illumination (ICWI) with Thales’sX-band active phased array radar (APAR), (2) linkfunctional and interface requirements, also due toAPAR, and (3) inertial midcourse guidance forSM-2 ER due to the need for portability of thismissile system type to non-Aegis platforms thatrequire an Area BMD and advanced TAMD capa-bility. (Inertial midcourse guidance is simply thedevelopment and execution of missile accelerationcommands onboard the missile, as opposed to beinglinkedbythecombatsystemaswiththeAegisCombat

Development of an ICWI-capable SM is first beingimplementedonSM-2BlockIIIA.

TheconceptoftheTFCsystemistactically,tech-nically,programmatically,andfiscallysound:asingleX-band,active-arrayMFR,basedoncommercialcom-ponents, that supports detection, tracking, linking,andillumination.Therearenodedicatedilluminatorson the TFC system. By having an MFR with thiscapability,andnothavingdedicatedilluminators,thesystemisabletoatleastdoubleitsfirepower;however,becausetheradarmustcoordinateRFresourcesforall

Goalkeeper

Smart-L

APAR

Goalkeeper

SonarFW-system

active

passiveHarpoon

Torpedo tubes

NH90

LCF, The Netherlands

F 124, Germany

Mk 41 VLSSM-2ESSM {

Figure 15. TFC combat systems.

Kauai Kokee site(3800-ft elev.)as surrogateair platform

Aegis CGmissile initialization

and midcourse

Aegis/SM-2midcourse

uplink/downlinkStandard

Missile

SPG-51D

CEC

Track/illuminate

Search/cue

Composite trackdevelopment

BarkingSands

BQM-74

Patriotradar

SPY-1B radar horizon

Joint TacticalInformationDistribution

System

RSTER ADS-18

System.)The development of ICWI for

SMstarted in the springof1997.This effort was initiated by theTri-lateral Frigate Cooperation(TFC) Consortium consisting ofThe Netherlands, Germany, andCanada (Canada is only anindustrialpartnerat thiswriting).The TFC Combat System is thenext-generationcombat systemofThe Netherlands and Germany(Fig. 15). These combat systemsarebasedonthelong-rangeL-banddetection radar, SMART-L, andtheX-bandMFRAPAR(Fig.16).


M. MONTOYA

Figure 16. SM Allied navy multifunction radar options.

functions,andbecauseitisaphasedarrayradar(nota dish), SM had to be changed to support illumina-tionwith interruptions(ICWI). ICWIispossibleonthecurrentfamilyofSMsowingtothecreationofthedigitalrearreceiver,discussedearlier,whichisdesignedtoremoveclutter-derivednoise.Withthedigitalrearreceiver, SM is able to synchronize in time and fre-quencywithaMFR’swaveforms,whichmakesICWIpossible.OlderanalogrearreceiversonSMwouldnothaveallowed ICWI tobepossible in sucha capableandefficientmanner.

APLhascontributedtoICWIdevelopmentfortheTFC with systems engineering, requirements devel-opment, missile and radarmodel development,Guid-anceSystemEvaluationLaboratorytesting,andCaptiveSeeker testing. The first live firing demonstrations ofanICWI-capableSMwilltakeplacefromtheGermanfrigate (F 124) during the last quarter of 2003. TheNetherlands’missile test firingshavenotbeen sched-uledtodate.

Also under way is the development of a multifre-quency, adaptable, link communication system. Theinitial concept for a new link communication plateoriginatedwiththeneedtointegrateSM-2ERonTFCsystems.CurrentlySM-2BlockIVAisonlysupportedviaahigh-data-rateS-bandlinkusedonAegissystems.However,sincetheTFCbaselinesystemdoesnotusean S-band radar system, and the consortium wishesto support Area BMD, the SM-2 ER communicationsystem(aswellasotherSMsystems)willbechangedtosupportXband.Incoordinationwiththiseffort,thereisalsoaseparateneedtoallowtheSMfamilyofmissiles,alongwiththeEvolvedSeaSparrowMissile(ESSM),tocommunicatewithRaytheon’sSPY-3X-bandMFR.All

of thesesystemrequirementsarebeingcoordinatedtodevelopasingle,universalcommunicationlinkforSMandESSM.

Thefinalrequirementsforthisuniversallinkareyettobedetermined,butallevolvingcombatandradarsys-temsfromothercountries(Fig.16)willbeconsideredinthiseffort.Developmentofthisuniversallinkbeganinmid-2001.Requirementsdevelopment,prototyping,ground testing, andflight testingwill bedonearound2001–2006.

The last area evolving for SM in support of ourinternational Allies is the potential development ofinertial guidance for SM-2 ER, and possibly SM-3.Again,theoriginsofthisneedstartedwiththeTFC.As background, SM-2 Block ER performs midcourseguidanceusing theAegisCombatSystem.Function-ally,commandmidcourseguidancehastheshipsendaccelerationcommandstothemissile,whichthemis-silethenexecutes, toallowforpropermidcoursetra-jectoryshapingthatsupportshandovertomissileter-minalhoming.

Currently the weapons used by the TFC system,SM-2BlockIIIAandESSM,bothhaveinertialmid-course guidance capability, so command midcourseguidance is not needed. However, the need for anAreaBMDcapabilityfortheTFCcountriescreatestheneed to implement inertial midcourse guidance inSM-2ER.

InitialfeasibilitystudieshavebeenperformedbyAPLtoensurethatthisinertialmidcourseguidanceisrobustandviable.Development and implementationwill bedoneinafashionthatensuresthatSM-2ERisportableto any system platform, has minimum system require-ments,andallowscontinuedsupporttotheAegis-basedFleet(Fig.17).Systemfeasibility,requirements,devel-opment,andtestingforthiscapabilityareplannedforaround2002–2008.

BaselineSMssuchasSM-2BlockIIIA(CWvariant)arestillbeingsoldtoourAlliestosupporttheirmissiledefenseneeds;however,a robustandflexible interna-tionalinteroperabilitylife-cycleapproachallowsSMtoimplementmissilesystemcapabilitiesbasedoncountry-specificrequirementsandnationalneeds.

CONCLUSIONThe evolution of SM, which has its roots in the

very beginnings of Navy surface defense, has main-tained success throughout the years based on soundsystems engineering principles as well as a validatedupgrade approach. Thus, SM is the springboard formany of the Navy’s developmental efforts. And, astheNavyaddressesfuturemissions,SMwillevolvetofulfill these multimission needs with a systems ap-proach, just as it has traditionally done since post–WorldWarII.

Italy UnitedKingdom

EMPAR (C band) Sampson (S band)

The Netherlands and Germany

APAR (X band) SMART-L (L band)



THE AUTHOR

MATTHEWMONTOYAiscurrentlytheTechnicalDirectionAgentfortheSMProgram,ProgramManagerforSMsystems,andADSD’sCoordinatorforInterna-tionalProgramsDevelopment.Mr.MontoyareceivedaB.S.inengineeringphysicsfromColoradoStateUniversityin1985,andM.S.degreesinappliedmathematicsandsystemsengineeringin1993and1995,respectively,bothfromTheJohnsHop-kins University. He has been involved with SM since 1986 as a systems analystandengineeraswellasprojectandprogrammanager.HehasservedtheSMPro-gramthroughlife-cycletechnicaldirectionwithconceptandrequirementsdevelop-ment,ATDengineeringmanagement,EMDengineeringmanagement,tiger-teamtechnical direction, production/transition engineering, Fleet-in-service engineer-ing, and internationalproductdevelopment.Mr.Montoya is theoriginal authorof the Future Standard Missile Strategy, which now serves as the basis for allSM development, engineering, and infrastructure support. His e-mail address [email protected].

Figure 17. SM-2 ER midcourse guidance options (blue, unchanged from baseline; orange, modified from baseline; green, added to baseline).

REFERENCES1“TheFuze,”Chap.1,inAPL—Fifty Years of Service to the Nation,JHU/

APL,Laurel,MD,pp.1–20(1993).2“Bumblebee,” Chap. 2, in APL—Fifty Years of Service to the Nation,

JHU/APL,Laurel,MD,pp.21–56(1993).3Kelly,M.R.,“TheTerrier,”APL Tech. Dig.,18–26(Aug1965).4Oliver, M. E., and Sweet, W. N., “Standard Missile: The Common

Denominator,”Johns Hopkins APL Tech. Dig.2,283–288(1981).5Amsler,B.E.,Eaton,A.R.,Floyd,J.F.R.,Goldbach,F.P.,Sheppard,

T.W.,etal.,The Tartar Missile: Adaptation of the Terrier Missile to Small Ship Use,TG258,JHU/APL,Laurel,MD(13Oct1955).

6Eaton,A.R.,“BumblebeeMissileAerodynamicDesign:AConstantinaChangingWorld,”Johns Hopkins APL Tech. Dig.13,69–81(1992).

7Zinger,W.H.,andKrill,J.A.,“MountainTop—Beyond-the-HorizonCruiseMissileDefense,” Johns Hopkins APL Tech. Dig.18,501–520(1997).

ACKNOWLEDGMENTS:Theauthorwishestoexpressappreciationforthespe-cialcontributionofAlvinR.Eaton,whoseextensiveknowledgeofAPLhistoryis reflected inthisarticle.Special thanksalsotoRobertL.HayesandJamesD.Flanagan.

EncoderDecoder

Command guideLink message

Processing

Missilesoftware

algorithms

Linktransceiver

Inertial guideLink message

Processing

Midcourseguidance

algorithms

Linkdata

emulator

IRUdata

Notional functional flow

Function neededto ensure minimum

changes tomissile software Option that improves

missile state estimatoraccuracy

Linkdata

Link

Initializationmessage flag

standard missile: a cornerstone of navy theater air missile defense

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