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Soviet Solid-State Dye Lasers: Technology Available for Frequency-AgileJ^Iilitary Laser Systems
A Scientific and Technical Intelligence Report
Dirtetorau of lutUittnci
Soviet Solid-State Dye Lasers: Technology Available for Frequency-Agile Military Laser Systems |
A Scientific and Technical Intelligence Report
Summary
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Solid-State Dye Lasers: Technology Available for Frequency-Agile Military Laser Systems^
The Soviet militarys preparing to dcploj aS. solid slate dyelaser systems designed to haw variable output wavelengths in order to complicate Western counter measures. Sustainedf dye laser techrwlogy provide* ihe key evidenceong-term interest in frequency-agilehe military wiT
specific systems for target acquisition, tracking, and blinding.
- identified some of the systems that the Soviet military wants to pursue, but wc believe there may be others. Initial systems,ountcrmcasurc-rcsistani target locator, could be deployed beginning in IhcP
Soviets have proven, solid-state tunable dye laser technology ready for incorporation into military and civilian development programs. In addition to offering frequency agility, these solid-state dye lasers are rugged, reliable, and welt suited to battlefield, airborne, and spacebomeThe laser technology results from nearly two decades of military-sponsored research intended toariety of applications.in addition to the countermeasure-resistant target locator, include blinding systemsaser to damage enemy optical systems on the battlefield. The Soviets also arc interested in upgrading previouslymilitary laser systems to make them resistant to simple (single-frequency) counter measures J
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The L'SS&hai the advantage of having the world's only sol id-state dyetechnology. Moreover, the Soviets are investigating other laserthat offer frequency agility and high reliability. Because of their demonstrated interest in this field, we expect the Soviets, despite defense cutbacks, to continue pursuing new tunable laser technologies. Some of these technologies probably will be available to military system designers in the next few years
To defeat Soviet solid-state dye laser systems, the West will require wavelength independent countermeasures.eans must be found to reduce the optical cross sections of all optical systems to contend with the tunability associatedoviet low-power-level laser target locator. To defeat tunable laser damage weapons, ways must be found to limit the intensity of light passing through Western optical systems. Finally, with the potential Soviet development and use of solid-state dyeimilar threat to the West could emerge from the Third World or subnationai organizations through the export of Soviet solid-state dye elements.!
GQtatMtt
Note
Quick To Recognize the Significance of Tunable Solid-Stale Lasers
Military Funds the Developmentechnology Bate lor Military Applications
Objectives and Milestones of the Soviet Program
the Firu Chalkngc. Single-Pulse Host Optical Strength
New Problem Optical Strength of (he Host Under Repetitive Pulses
Last Hurdle; Dye Optical Strength
Fixes to Last Minute Glitches. Good Optical Strength Begets Poor Mechanical Properties
Beit: Alternative Solid-Stale Host* and Lasants
Acrylatc Possible Successor to Problem-Plagued Polymethy! Methacrylatc
Quartz: Low-Pi: lie-Energy Application.
Lasam. Limited Tuiubihty
Applications
Locators. Antisensor Weapons, and Blinding Weapons
Pumped Lasers To Be Fired From Existing Air Defense Gun System.
to the Third World
(or the L'nitcd Sutes
ycle
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Scop*scientists and engineers have been developing solid-state dye laser
strong support from the Sovietmore thanears. In this paper, we examine the technical objectives, milestones, and general progress in the technology development. We also assess known, likely, and possible Soviet military applications of this tunable laserand we estimate the likelihood, ofdevelopme.n'. and Ihe deployment times for these military systems I
research community
The principal results of our analysis are intended to be used by US military systems designers to develop appropriate countermeasures to future Soviet laser systems. In addition, the unique Soviet approach to the development of rugged tunable laser technology may be of value to the US laser
Soviei Solid-Slate Dye Lasers: Technology Available for Frequency-Agile Military Laser Systems|
Soim Quick Totbe Sigalneanee of Tenable SolM-Statc Lasers
In the, scientists throughout the world were rapidly developing new laserasers based on solid-state materials, including glosses and crystals, proved to be compact, rugged, and generally reliable. In tbe USSR and the West, solid-state .lasers quickly became critical components in military and industrial systems. As range tinders and targetsolid -siate lasers proved valuable on tbe bat lie-field One hmiutioo on their use. however, was that the emissions of solid-state lasers could not be tunedesired vavelcngth. Being restrictedew (Wed wavelengths made these lasers susceptibleariety of counlermeasures.
For those applications requiring tunabiiity. scientists in the USSR and the West turned to lasers based on organic dyes in liquid solutionselection ofqaid-dye laser could be tuned from near infrared wavelengths through the entire visibleHowever, tbe liquid-dye lasers were bulky, unreliable, and generally poorly suited to applications outside the In
wo US scientistsechnical paperaser based on an organic dye contained within -solid polymer matrix. They had noticedrafting square composed of dye-colored pcJymethylknownowerful laser beam would itself laseavelength determined by the dye in the plastic. They also noted, however, that the lasing efficiency was low. Little followup research was conducted in the United Slates kaH
Soviet scientists, on the other hand, were quick to grasp the potential of solid-state dye lasers. Insections to technical papers published in the, the Soviets noted that, as compared with dyes in liquid solution, dye-activated solid polymer lasers potentially could be made more simple, more
compaci, easier to manufacture, and much more reliable in fieldt is not clear if the Soviets bad specific military applications in mind ai the outset of tbeir research into solid-siate dye lasers, but are believe that the Soviet military had these general advantages in mind when it sponsored the research activity frojD_whichvariety of applications could evolve.
Soviei Military Funds tbe Devclopmenl
echnoloay Base for Military Application
of dye solution
solid-state dye technology wasto provide Soviet laser systems with variable output wavelengths in order to defeat Western optical protection and to resist countermeasures. Throughout, the Soviet military jlanncdjp become increasingly dependent on.User system* tocquire information on enemy targets and.to direct
' Lkju id-solution dye laseisargeirculatory pumping syjietn
precision-guidctl munitions against them. With the expectation (hat reliance on laser systems would grow the Soviet* also had to address the threat of potential counicrrncaiurcs. Enemy forces could delect Soviet fixed wavelength laser emissions and direct tire back onto critical surveillanceoviet smartthat focused on target reflections or emissions could be spoofed with samc-wavclcngth lasers. Solid-staie dye technology offered theeans to
vary the laser outputroad wavelength spectrum, thus defeating simple countcrmeasures
Soviet solid-state dye technology probably waswith the broad goal of providing Soviet military -systems designers with nigged, frequency-agile lasers for integrationariety of ground, airborne, and
spaccbornc laser applications. The direction* olresearch, as well as statements b> Sovietin technical review articles, suggest thai the technical goals of the Soviet research program werenicnckd loroad range ofWe know of some specific applications,later in this report, but Soviet research activity seems to have been aimedide range of possible uses of dye lasers
The directions taken in Soviet solid-state dye researchesire to achieve frequency agility while retaining the overall reliability and performance of existing fixed wavelength lasers For example, the Soviet* investigated organic dyes wiih emission bands from the near infrared through tbe near ultraviolet range of the electromagnetic spectrum, indicating no application-specific band of interest Single- andoptical damage of polymer hosts were investigated with the goal of achieving "equivalent performance to opticalhe implied objective was toolid-state dye element that could be incorporated into existing Optical system* without limiting overall system performance I
Soviet technical review articles published in theescribed research goals in terms of classes of applications Authors wrote that solid-state dye lasers wouM be particularly well suited to ground, airborne,ace borne laser applications because such lasers could operateide range of temperatures and under zero-gravity conditions. Liquid-solution dye lasen, by comparison, already were perfectly adc-quale for laboratory and industrial use. |
Technical Objectiies and Milestones of the Soiiei Program
At first. Soviet scientists suggested that solid-state dye laser technology would mature quickly; however, this belief was not the case. Researchersariety of Soviet Institutes soon began to identify numerous impediments to the development of this technology. They Included:
The optical strength of the solid host material (its resistance to optical damage).
The optical strength of the dye (resistance to photobleaching).
The critical quality of the combined materialH
Soviet RAD Cycle
Soviet military systems ore developederies of highly regulated stages. The process
Beginsorecast 'prognoU-
Progresses into several stages of Scientific Research Work :nauchno-lssledovalcr>kaya rabota. or NIRf.
Proceeds to Experimental Design Work ,'opyinokon-strcktorskaya rabota. or OKRf
tniers too productionJ
Major decision points mark ike transition from one stage to another Research to lay the snentdic-technieal base for use In future military systems is conducted within NIR Requirements generation,of technology for new systems, and design alternative evaluations also art conducted during PilR. Design and construction of system-specific test components and prototypes of Items Intended for production are accomplished in OUR |
To overcome these impediments, formalwork or NIR (see insetl was initiatedariety of Soviet institutes teamedsolve tbe specificAs tbe
research progressed,nTcalpeooTems were ericountered and additional research efforts wereSeveral alternative solid-dye technologies were developed in parallel by competing institutes.
Soiling the Flnl Challenge: Single-Puts* Hot! Optical Sirenglh
Primarily from openly published technicale believe that tbe Sonets in0 first recognized the tingle-pulse optical strength of polymer materialsimiting factor inaser(sec3 technical paper. A. A. Manenkov of the Institute of Physics in Moscow described experimental results of laser-inducedbreakdown of polymcthyl methucrylate and other optically transparent polymers Manenkov determined that ihe optical strength of commercial polymethyl methacrylatecgawati pei centimeter squared (MW'/cm'ianosecondorders of magnitude lower than for optical glass and far too low to be usedractical laser material. In what was to become the focus of moreecade of research. Manenkov suggested thai the optical strength of polymcthyl methacrylate could beby reducing the concentration of impurities.
Working in conjunction with the Scientific Research Institute of Organic Intcrmediaie Products and Dyes. Manenkovrocedure for manufacturing opiical-quahiy polymcthyl mcihacryiaic. According io open technical papers and statements by Manenkov |special procedures wereethacrylateto reduce particulate impurities. In addition, special polymerization procedures were adopted to reduce the concentration of voids and otherOn the bast* of Ihe optical strength of poly-meihyl methacrylate reported by Ihe Soviets atconferences and in open publications, we believe that, by the, the Institute of Physics in Moscow and the Scientific Research Institute of Organic Intermediate Products and Dyes badsamplesa single-pulse optical sirength ofthat of optical-quality Glass J
Optical-quality polymethyl methacrylate appears to havevied
but quality,
may have hindered practical applications.ariety of institutes published articles in theescribing laser systems
incorporating polymethyl-methacrylate-basedlenses, however, may have come fromof Physics in Moscow rather thanManenkov complained repeatedly atconferences in thehatwas not able to match the quality ofmethacrylate produced at his institutebe staled that industry could notpurity required to achieve sufficientWe have insufficient information toexactly when Soviet industry solved this by the,
i^iTi^uTOlics of optical-quality polymethylas determined by their published reports.
A New Problem; Optical Strength of tbt Must Under Repetitive Pluses On the basis of their published results, we believe Soviet scientisn realized in thehat, after repeated use, optical damage would occur inmethacrylate at significantly lower intensities than the single-pulse damage limit. Experiment*in scientific papers is tbeclearly that, unlike glass, optica! elements made of polymethyl methacrylate showeddamage after repetitive laser pulses of several orders of magnitude of less Intensity than the single-pulse damageinhibiting most practical applications. Inundamental shift in the Soviet icchnic.il literature occurred in theoviets geared up to address this limitation.
The technical literature indicates thai several Soviet institutes pul forth theories to explain ihe anomalous low-repetitive-pulse damage limit. Scientist* at (he Scientific Research Institute of Organic Intermediate Products and Dyes suggested that tbeas due to overheating and carbonization of ihe polymer in the immediate vicinity of any light-absorbing impurities. The region of absorption and resultant damage would grow from pulse to pulse. Their theory suggested no ready solution other than trying to further reduce the initial concentration of impurities.|
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Manenkov. od Ihe other hand. suggested that the growth of absorbing defecurelated to the raco-cUitic propertiei of the polymer, not to its chemical composition. This theory implied thai, by modifying ihe viscoclastic properties, the repetitive-pulselimit could be made to converge on the single-pulsc damage limit, gaining al least several orders of magnitude improvement.9 technical paper.
Manenkov reported experimental results suppewting his theory. In these experiments, the viscoelasirc properties were varied byighly volatile plasticiier in the polymer or by altering the temperature of the samplesroad range-ndegreesn each case, the
single-pulse, bulk-damage threshold was determined by exposure of the polymernanosecond ruby laser pulse. The repetitive-pulse opticalas determined by repeated exposure to radiation pulsesixed subthreshold intensity, and the sirength was reported as the number of laser pulses that could be applied before tbe appearanceeters) damage in the mairix. Tbe resultsefinite correlation between the viscoclastic properties and the optical strengthH
Soviet technical literature indicates that in theanenkov was successful in fabricating poly-methyl-met hacry late-based optical elementsepetitive-pulse optical Strength equal to glass.anenkovlassic paper entitled "Transparentew Class of Optical Materials for Lasers" with A. M. Prokhorov, deputy director of the Institute of Physics in Moscow, and V. S. Nechiiailo. team leader from the ScientificInstitute of Organic Intermediate Products and Dyes. This paper reviewed the formulation of Manenkov's optical damage theory, the experimental confirmation of the theory, and the development of polymethyl methacrylate capable of withstandingoptical intensities of greaterW/cm1 based on implications of the theory.concluded by stating that transparent polymers already are available that may be competitive with traditional materials in high-optical-strength elements (for example, lenses or prisms) and they undoubtedly have advantages in specific laser components as active elements (solid-state dye lasers) and passive switches.
Few technical papers were published3 on the optical strength of polymcthyl methacrylate.that this aspect of the research had been completed. In addition, the use of opticallypolymethyl methacrylate in Soviet (nonlasingl optical elements became common byuggesting that Manenkov's polymcthyl methacrylate had entered series production. It is possible, therefore, that the Sovietsecision to proceed with the development of military dye lasers at about this time. As discussed below, however, other technicalarose that probably forestalledecision.
The Last Hurdle: Dye Optical Strength
The incorporation of dyes into solid-state hostcreated new problems. Scientists from theResearch Institute of Organic Intermediateand Dyes identified the lifetime of the dyeritical issue.6 technical paper.oted that dye moleculesolymer elemeni were rapidly denatured duehoioblcachingHe suggested that new dyes were needed with greater resistance to photobleaching and that methods Of Stabilizing dye moleculesolymer mairix would be required. I
increased the lifetime of solid-state dye elements up to that of the host material by encapsulating alcohol and other additives with the plasticizer. According to Manenkov, the alcohol interacts with dangling bonds created by photodissociation and prevents theof (he dyes.
Quick Fixes to Last Minute Glitches: Good Optical Strength Begets Poor Mechanical Properties
Although each of the original problems had been addressed and independently resolved by the, the methods of resolution had created an additionalmodified polymcthylwas not easily machined into an optical element. In particular, polymethyl methacrylate
doped withplasticizcrs (toihe host'* optical strength to repetitive pulses) is much less rigid than commercial polymethyl metUlc Thus, the material was difficult to machine to close optical tolerances, and large elements did not retain their shapes By changing the vtscoelasticto accommodate repetitive pursing, polymcthy! methacrylate had been rendered unsuitable (or final shaping and incorporation into active laser elements.
Scientists from the Institute of Physics in Moscow and the Scientific Research Institute of Organic Intermediate Products and Dyes turned with apparent success to chemical etchingethod of achieving an optical surface on modified polymeihylAs revealed in technical publications in the, chemical etching removed microscopic surface defects created by mechanical polishing. The reported optical characterise were_sufhcicm for incorpora-lion into laser sytlce
Attempts to incorporate modified polymethylinto laser systems revealed one last problem. The rubbery material deformed when heated under optical pumping. Again, the scientists respondeduick engineering solution.ate 1
wedged slab* of modified polymethyl methacrylate between sapphire plates This combination kepi the polymer suiTtciertily rigid and improved the overall heat transfer rate as well Manenkov claimed to haveigh repetition rate (probably aboveulses per second) with this confi . J
Hedging Bets: Altcrnallse Solid-Slate Hosts and Lasants
Pvlyurrthant Acrylalt: PowHf Smtfttsar toPlatata" Polymethyl Sletmterylmie. Aspolymethyl methacrylate team was windingew research team emerged in Kiev to pursue polyureihane aeiylate as an alternative solid-mateurge of scientific papers appeared In the, written by scientists (rom the Institute of Physics in Kiev and the Institute of High-Moiecuiar Compounds of the Ukrainian Academy of Sciences. The papers demonstraied thai polyureihane acrylate had greater potentialolid-slate dye host than
The key to success with polyureihane acrylatc was its unique polymer chain linkages that resisted stress failure. The scientists simply formed the solid-state dye elementsuiplea" by radical polyTreeriza-non of the monomer between two plates of quartz or sapphire with oplical quality surfaces. Ulirapurifica-tion of the monomer was not required nor were special additives Also, no additional polishing or finishing was requited Tbe reported optical strength of poly-ur ethane aery late was shown to be comparable with the strength of optical0 MW/crat Without much fanfaic. these componeni materials entered limited production in the tale I'
Microparout Quartz Low-Puhe-EnergyOlhcr solid-stale materials also emerged in thehese materials demonstrated superior performance, as compared withore limited set of condition*he deputy director of the Institute of Physics in Moscow,rokhorov. and the director of the Scientific Research Institute Polyus. General Stcl1-makh.andmark paper with scientists from the Institute of Precision Mechanics and Optics io Leningrad,ew solid-state dye host with high optical strength. By leaching borosilicate glass in concentrated acid, theyicropo-reus quartz material. This material was shown to have nearly the same optical strength of solid quartz and could be manufactured with readily availableWhen submergedye solution, the micro-porous quanz became saturated with dye and solvent molecules. Laser action* could be achieved cither with the solvent present or following evaporation
With no inherent difficulties to overcome,quartz solid-state dye elements entered limited production in the. An unclassified article published in4 described the optical strength of microporous quartz already available in limited production. Single-pulse damage ihrcsholds were
reported for the iiirfacc arid tbe bulk material with and without dye. la all cases, tie damage threshold was lessno lower thanforrade glass. Impurities associated with the dye appeared to lower the optical strength of microporous quart', and it was suggested thai. b> betterof the dye solvent, the optical strength could be rloiihJ!
Nevertheless, microporous quartz could not be scaled up to high-pulse energies and, thus, waseal competitor to the polymers.hin layer of glass could be etched, dye concern rations were inhomogen-cous. and the microscopic structure distorted and scattered the optical radiation. Although severalapplications were demonstrated, the number of scientists involved in ihe research decreased toew specialists in the
Atternath* Iashm; Limiittt Tunubiliiy. In theQs, several competing solid-state tunable laser technologies were discovered. Ions in crystal lattices, such as alexandrite, emerged as reliable sources of tunable near infrared laser emissions Color-center lasers extended this tunabihty deeper into the infrared band but provided only marginal reliability.optical techniques, such as optical parametric oscillators and frequency-conversionompletely solid-stale approach to obtaining frequency-agile emission in limited spectralfrom the near infrared through the visible spectrum. For applications requiring only limited tanabilny (such as some remote chemical-detect km applicatioro conducted at the Institute of Atmospheric Optics inhese advanced technologies could compete favorably wiih solid-state dye lasers. But for true broad-band (unubility. dye laser* remain the only viable opli
Likely Applications
Target Locators, Antisensor Weapons, ami Blinding Weapons target locators and antisensor laser weapons (see|
wavelengths, was to be incorporated inio an armored vehicle to be deployed on the from-hnes The original purpose of the device was to locate targets by sweeping the battlefieldaser beam and detecting tbe reflection from enemy opticalAn upgraded device wa> planned,igher power solid-state dye laser, to blind or destroy sensors and to blind enemyjj
dye lasers were developed to pro vide courttermeasure resistance in military laser
The developmentu III wavelength laser system for useattlefield blinding weapon wouldormidable threat to US and NATO forces for two principal reasons. First, target acquisition by gunners of most ground-based and hclibornc weapon systems and by pilots of attack helicopters, tactical fighters, and ground attack aircraft is heavily dependent on vision. Thus, Soviet blinding of US/NATO gunners or pilots, even if onlyhort lime (often calledouldatastrophic impact on their ability lo engage Soviet forces on the battlefield.
Second, dye lasers can emit optical radiation al many wavelengths throughout the visible spectrum. Because of thisye-laser blinding weapon could easily be designed to counter current US and Western laser protectionprotect only against specific wavelengths. Currently, protection techniques toultiwavelength laser threat (such as fast optical switching or limiting the opticalight) are not sufficiently mature for production and fielding.
Wc assess that (he second-genera lion laser locator system probably willow-powerooules) laser, incorporating several solid-state tunable dye
Open technical publications from theink V. S. Zuyev to scientists from both the Design Bureau Astrofizika and (he Scientific Research Institute of Organic Intermediate Products and Dyes. These pub-lications describe dye laser emissions from the vapor phase at high temperature andrelated to explosivetherearenoof explosive pumped polvmcrs.H
We believe that the Soviets could have begun OKR for explosively pumped laserby ihc. Tbe published Soviet results suggest that there are no technical difficulties associated with the design or construction of explosively pumped dye lasers, and the award presented to the participating scientists suggests some degree of success. Low-optical-strength polymers can be used because repetitive pumping is not an issue. In addition. US studies have shown that explosively pumped solid-state dye lasers can beand rugged and can be manufactured with
Assuming that the Soviets commenced OKR in the, deployment could have begun by thee believe that the Soviets most likely would have designed explosively pumped User devices to fit the constraints of existing air defense gun systems The inclusion of explosive laser rounds in thr standard gun magarine couldegree of protection torn airborne targets byjlefeat^nd visual-sight tag systems during an engagement As yel. however, we have no evidence of deployment. I
Sain tn (he Third World
Consistent with the overall restructuring of the Soviet economic system, the current restructuring of Soviet scientific research programs may influence Soviet scientists involved ia solid-state dye technology to pursue externalThird Worldmarkets In the USSR, as in the West, there is little commercial need for solid-state dye technology.
Semiconductor lasers arc used in most Soviet low-power tunable applications, such as optical-fiberand solid-staie crystallise lasers provide the minimal tuaabtlity needed in most environmental rcrr.otc-scr.sing applications
Third World nations could view solid-stoteost-effective means to defeat military electro-optical systems. In particular, the use ofpumped dye lasers could be used by ground forces to defend against advanced belicopiers and ground support aircraft. Many Third World countries have the necessary technology base to incorporate Soviet solid-state dye elements into military systems.
for ihe United States
year Soviei investment in solid-statetrong commitmeni to couniermea-sure-resistant laser systems and lo laser systemsof defeating Western countermeasures Although wc believe dye-laser locator and laser weapon systems en:ered OKR during, wc cannot be sure that tbe Soviets actually will deploy an> military Laser systems based on solid-state dye technology Although dye lasers provided the only option for tunablethrough the,ersuch as crystalline lasers and nonlinearemerged in the past decade as potential candidates for future applications thai require only limited tunabili-ty. Currently, Soviet military systems designers can chooseange of technology options, depending on the wavelength range of interest and the degree ol tunability desired^
To defeat Soviet solid-state dye laser systems,countermeasures will be required. To contend with the tunability associatedow-power-level laser target locator, ihe West will haveonsider ways to reduce the integrated optical cross secuora of all optical systems. The reduction of the integrated optical cross section may require theof new technologies and may degrade the performance of optical systems.
To defeat tunable laser damage weapons, the West will have to consider ways to limit the intensity of light passing through optical systems. Whereas fixed wavelength laser weapons can be counteredtatic, narrow-bandynamic shutter will be required to protect against tunable lasers.because dye laser pulses can be made extremely short Ion the order ofhese shutterswill have to react on an extremely short nmcscalc.B
In addition to potential Soviet use of solid-state dyeimilar threat could emerge from the Third World or subnaiional organirations. If the Soviets export solid-state dye elements, tbey could be integrated into relatively simple but elective blinding and antiseitsor laser weapons. These low-cost weapons might be very attractive to Third World countries or subnational organizations for their ability to counter advanced helibornc and airborne electro-opticaland to blind pilots. |
do noi believe thai cutreni Soviet defense cui-backs will necessarily affect Soviet tunable laser programs In general, any decrease in the number of weapon platforms deployed is likely to increase the seed for improved couniermea sutes resistance. The Soviets probably consider electro-optical systems like the laser locator to be good force multipliers because tbey allow many more targets to be engagedingle platform In addition to the automatic location of targets and destruction of sensors, the laser locator can servearget designatorariety of other weapon delivery plat for
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