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2

Present and Projected Theater Missile Threats

2.1 TACTICAL MISSILE PROLIFERATION

The current proliferation of cruise missile technology is extensive and accelerating. A partial listing of the ASCMs that are being produced and sold on the worldwide market includes variants of the following:

  • Aerospatiale Exocet,

  • BAE Sea Eagle,

  • IAI Gabriel,

  • OTO Melara (Breda) Otomat,

  • Saab RBS-15,

  • MDAC (Boeing) Harpoon,

  • SS-N-25 Harpoonski, and

  • Russian SS-N-22, 26, and 27 supersonic missiles.

Briefings to the committee about the threat dramatically illustrated the scope of this proliferation. Several factors appear to be fueling this growth. The Gulf War and other conflicts made clear the political impact and value of such weapons to lesser powers and helped create a ready market in consumer countries whose wealth comes from oil.

Russia's need for hard currency has made it willing to market its most modern weapons. China's growing missile technology capability and apparent willingness to export that expertise, along with the marketing efforts of European weapon suppliers, make it likely that the United States will encounter significant numbers of these weapons in any future operations.



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Page 25 2 Present and Projected Theater Missile Threats 2.1 TACTICAL MISSILE PROLIFERATION The current proliferation of cruise missile technology is extensive and accelerating. A partial listing of the ASCMs that are being produced and sold on the worldwide market includes variants of the following: Aerospatiale Exocet, BAE Sea Eagle, IAI Gabriel, OTO Melara (Breda) Otomat, Saab RBS-15, MDAC (Boeing) Harpoon, SS-N-25 Harpoonski, and Russian SS-N-22, 26, and 27 supersonic missiles. Briefings to the committee about the threat dramatically illustrated the scope of this proliferation. Several factors appear to be fueling this growth. The Gulf War and other conflicts made clear the political impact and value of such weapons to lesser powers and helped create a ready market in consumer countries whose wealth comes from oil. Russia's need for hard currency has made it willing to market its most modern weapons. China's growing missile technology capability and apparent willingness to export that expertise, along with the marketing efforts of European weapon suppliers, make it likely that the United States will encounter significant numbers of these weapons in any future operations.

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Page 26 2.2 CRUISE MISSILE THREATS The weapons referred to in this study under the generic title of cruise missiles can be ground- or air-launched. Ground-launched cruise missiles are generally multistage missiles, with the first stage being a rocket. At some predetermined altitude, the rocket booster is discarded and wings or canards are deployed to provide aerodynamic lift. Simultaneously, a motor is activated to provide propulsion. Air-launched cruise missiles are carried to launch altitude by an aircraft. In this case, too, tail fins, wings, and/or canards may be deployed to provide trajectory control surfaces. A cruise missile may be accelerated to cruise speed by a rocket booster and might be designed to employ rocket thrust for a high-speed terminal attack. For most of its flight, a cruise missile is propelled by air-breathing turbojet or ramjet engines and relies on aerodynamic lift to carry its weight and maintain altitude. Cruise missiles remain within the atmosphere and under power during their cruise phase. Hence, their range and general flight characteristics are similar to those of an airplane. Payloads carried by cruise missiles may include large, unitary, high-explosive warheads, submunitions, runway penetrators, or weapons of mass destruction (nuclear, chemical, or biological). In the past, successful cruise missile attacks succeeded in sinking warships or causing severe, mission-limiting damage to them. Cruise missiles that are configured to carry and dispense submunitions constitute a particularly severe threat to troops in the field and to nonarmored vehicles such as trucks. When the submunitions that are dispensed by a cruise missile are high-performance, self-propelled devices that are equipped with terminal engagement sensors, they can even constitute a significant threat to armored vehicles. Thus, cruise missiles are a significant threat both to plat-forms at sea and to forces ashore. Cruise missiles can be classified according to the altitude and velocity of their cruise segment, as well as their launch-to-target range. Cruise altitudes fall into three categories: high altitude, low altitude, and surface skimming. High-altitude cruise extends the range by improving fuel-use efficiency, but it makes the cruise missile more likely to be detected. At lower altitudes, such missiles can take advantage of the decreased line-of-sight horizon for trackers in the vicinity of the target and of terrain features that mask the approach path. Surface skimmers, which are practical only over the ocean or extremely flat and desolate terrain, descend to within a few meters of the surface and may go undetected until very close to the target. Cruise missiles may cruise at subsonic, supersonic, or hypersonic velocity. Because lift-to-drag ratios decrease with increasing speed above the maximum endurance speed, a range penalty is paid for supersonic or hypersonic flight. However, since the time of flight is inversely proportional to speed, the intercept problem becomes more difficult as the speed of the target missile is increased. Of course, a cruise missile's flight path may be broken into

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Page 27 segments with different altitude-speed characteristics to maximize the probability of mission success. A cruise missile is not constrained to follow a single path to its target and can, in fact, follow a devious route to avoid obstacles and terrain, to hide below the tracker's line of sight, and to deceive defenders. While the thrust-to-weight ratio need not be large to maintain cruising flight, a cruise missile is easily designed to pull significant g load factors, allowing it to change direction quickly. Hence, it can jink, S-turn, and feint on the way to its target. It can approach its target a few meters above the surface or pull up and dive on its target at a high angle. To limit the ability of defending forces to maintain its trajectory in track, a given cruise missile can be programmed to choose apparently random approach maneuvers. Unlike a ballistic missile engagement, a successful intercept of a cruise missile before it approaches its target virtually assures that the cruise missile will fail to accomplish its mission. Furthermore, less damage may be necessary to defeat a cruise missile than to defeat a ballistic missile. Such a missile need not always be totally destroyed—degraded performance in the form of diminished accuracy for the guidance sensors or a partial loss of aerodynamic control authority may be enough to cause it to miss its intended target. Cruise missiles can attack both stationary and mobile targets. If a movable target is stationary for an extended period of time, the missile may be programmed to fly to the global positioning system (GPS) coordinate where the target is known to be located. Worldwide open access to the GPS and GLONASS (the Russian equivalent of GPS) networks simplifies the navigation and guidance systems for cruise missiles designed to attack fixed targets. Ten-meter navigational accuracy to any latitude-longitude pair is readily obtainable now that GPS selective availability (SA) has been turned off. One-hundred-meter accuracy is available with SA operating. In a major conflict, the United States might take measures to restrict the local availability of GPS to its adversaries. However, there is no precedent to indicate that during low-intensity operations, the operation of GPS will be restricted. Cruise missile attacks on moving targets are multistep processes. First, the missile must be guided to fly to a point where, based on a target track developed by an external sensor, there is reason to expect that the terminal sensor on the cruise missile will be able to acquire the intended target. If the intended target is within the acquisition basket of the missile's seeker, the seeker can acquire the target and the missile can guide itself on a collision course to the target. A wide variety of seekers have been developed to support the terminal engagement phase of cruise missile attacks. If the cruise missile does not have a data link back to an individual who can evaluate the output of the cruise missile's sensor and control the terminal engagement, it must be guided to the target autonomously. Autonomous guidance sensors are subject to jamming, deception, and decoys. ECMs against missile guidance and navigation systems have been em-

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Page 28 ployed since World War II, as have electronic counter-countermeasure (ECCM) techniques that are designed to negate the effects of defensive countermeasures. The ECM-ECCM battle is open-ended and will continue indefinitely into the future. The sensors on the newest missiles that are entering into the operational inventories of potential adversaries appear to have extremely robust ECCM capabilities against current ECM techniques. Advances in techniques related to automatic target recognition (ATR) tend to make seekers robust against distraction decoys. On the other hand, the fidelity with which modern decoys or repeaters can replicate the signature of the target of a cruise missile is impressive. Clearly, the Navy must continue an aggressive ECM program so that as new advances in seeker technology are fielded, new countermeasures will be available to negate them. Aside from the threat that improved cruise missile seekers pose to Navy ECM techniques, there are many trends in cruise missile design that the committee found to be a source of concern, including the following: Greater missile speeds, which limits the engagement time; Lower RCSs, which limits the range within which a missile may be detected once it has crossed the horizon of defensive radars; High maneuverability, which limits the ability of a defensive system to track and engage the missiles; Trajectories that make maximum use of terrain obscuration and clutter masking in littoral situations; and Sea-skimming flight paths, which keep incoming missiles below the horizon of defensive radars for as long as possible. Worldwide, cruise missile designs abound. Many of these designs already stress the capabilities of U.S. defensive systems. Table 2.1 lists some of the worst-case parameters of currently operational missiles and the committee's projections for the parameters that may be encountered in the next 15 to 20 years, based on its assessment of trends in technology. The first four attributes listed in Table 2.1 are intended to limit the options for engagement by defensive missiles. The fifth and sixth attributes attempt to defeat defensive ECM techniques. The committee's estimates for 2020 are extrapolated from current trends in missile technology. The sixth could leapfrog future ECM efforts. Although some members of the committee doubt that accelerations of 20+ g will be feasible, all of them concur that future cruise missiles will possess greater agility than currently deployed threat missiles. As missiles become more agile, the data rates of defensive systems must be increased and the track association algorithms of defensive sensors will require major modifications. Even if the RCS values of threat missiles do not decrease, their greater agility and speed will challenge the tracking algorithms and data rates of existing defensive systems.

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Page 29 TABLE 2.1 Attributes of Current and Projected (2020) Cruise Missile Threats Attribute Current Estimated for 2020 Agility 6 to 8 g maneuvers 10 to 20+ g maneuvers Nose-on radar cross section −10 to −30 dBsm −20 to −40 dBsm Altitude (sea skimmers) 2 to 5 meters 2 to 5 meters Terminal speed Sub- to supersonic Up to hypersonic Electronic countermeasure robustness Moderate Improved Guidance Global positioning system GPS and target recognition (GPS) and radar/infrared Under optimum conditions, these systems employ a defensive shoot-look-shoot (SLS) doctrine to conserve interceptors. If the defensive time line is compressed by some combination of changes in missile RCS altitude, ECCM, speed, and maneuverability, the capability of the defensive system will be reduced successively from shoot-look-shoot, to shoot-shoot, to shoot and, in the worst case, to no shot possible. The effects of RCS and Mach number are illustrated conceptually in Figure 2.1. The figure shows that for a sea-skimming incoming cruise missile attacking a defended ship equipped with only a surface-based sensor (or for such a missile at any given altitude), there will be a large area in the RCS-missile velocity plane where it is not possible to launch a defensive round. If the altitude of the attacking cruise missile is low enough and if its velocity is high enough, there may be no way to shoot the missile, even if it has a large RCS. In other areas of the RCS-missile velocity plane, defensive systems have an opportunity to launch either one or two defensive missiles or may even be unable to launch a single defensive missile. Most current cruise missile threats do not lie in the no-shot region. However, unless elevated sensors are used, or unless significant improvements in defensive capabilities are achieved, missiles with the attributes in the third column of Table 2.1 will generally fall into the no-shot region of Figure 2.1. In such a situation, the defense will have to depend entirely on the Navy's ECM capabilities to defeat the terminal guidance system. If elevated radars are used in lieu of surface-based radars, the radar horizon will increase significantly, somewhat negating the advantages of high speed. Of course, elevating the radar will not offset a reduction in the RCS value of the threat missile. The RCS value of a missile varies with both frequency and missile orientation. Thus, low-RCS missiles can only be defeated by using radars that operate at lower radar frequencies and/or by using some form of

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Page 30 ~ enlarge ~ FIGURE 2.1 Conceptual representation of the effects of radar cross section (RCS) and Mach number on the defensive capabilities of a surface-based sensor and associated missile system against a cruise missile attacking at a sea-skimming altitude. multistatic operation that allows the missile to be viewed from orientations where its RCS value has significant peaks. 2.3 THEATER BALLISTIC MISSILE THREATS 2.3.1 Characteristics of Theater Ballistic Missiles On September 26, 1997, agreements were signed between representatives of the United States and the Russian Federation that established the permissible characteristics of TMD systems. The 1st Agreed Statement permits either side to deploy lower-velocity TMD systems (those with interceptor speeds below 3 km/s) provided that they have not been tested against a ballistic missile target having a range greater than 3500 km or a speed greater than 5 km/s. (U.S. compliance review has independently determined that PAC-3, THAAD, and NAD systems are compliant with that agreement.) The 2nd Agreed Statement permits either side to test interceptors that are faster than 3 km/s against ballistic missile targets with velocities less than 5 km/s and ranges less than 3500 km. (The Navy's upper-tier TMD has been certified as being compliant with the ABM Treaty.) Strictly speaking, the 2nd Agreed

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Page 31 Statement only says that a requirement for being legal under the ABM Treaty is that such higher speed TMD systems must not be tested against targets faster than 5 km/s. However, this does not automatically mean they are compliant. With this delineation, one can define theater ballistic missiles (TBMs) as one- to three-stage liquid- or solid-propelled rocket vehicles that have launch-to-impact ranges of 100 to 3500 km. Although these limitations have not been submitted to, or ratified by, the Senate, the Clinton administration adopted them as policy. From first principles, TBM velocities at final-stage burnout must be from 1 to 5 km/s, while their post-boost times of flight vary from about 2 to 20 min (see Figure 2.2 ). After the powered phase of flight, a TBM flies in a vertical ~ enlarge ~ FIGURE 2.2 Minimum burnout velocity, maximum altitude, and time of flight as functions of range between burnout and reentry. Burnout altitude = reentry altitude = 10 km with Earth's rotation and atmospheric effects neglected. NOTE: This figure is approximate and actual values will vary according to more detailed scenarios. SOURCE: Calculations based on (1) Bate, Roger R., Donald D. Mueller, and Jerry E. White, 1971, Fundamentals of Astrodynamics, Dover Publications, Mineola, N.Y.; Thomson, W.T., 1961, Introduction to Space Dynamics, Dover Publications, Inc., Mineola, N.Y., December; (2) Thomson, William T., 1961, Introduction to Space Dynamics, Dover Publications, Mineola, N.Y., paperback edition, May 1986; (3) Sellers, Jerry J., and Wiley J. Larson, 1961, Understanding Space: An Introduction to Astronautics, Space Technology Series, McGraw-Hill, New York, N.Y.; and (4) Sellers, Jerry J., William J. Store, Robert B. Giffen, and Wiley J. Larson, 2000, Understanding Space: An Introduction to Astronautics, 2nd edition, McGraw-Hill College Division, McGraw-Hill, New York, N.Y., June.

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Page 32 plane between the launch site and the target. The time of flight and distance traveled during boost, a function of acceleration as well as staging, typically are small percentages of their respective totals. The corresponding maximum altitudes vary from about 20 to about 800 km depending on impact range and trajectory type (maximum-range, depressed, or lofted). A missile can be targeted at less than its maximum range by depressing or lofting the trajectory or by reducing the burnout velocity. Depressed trajectories to a given impact range have shorter flight times and maximum altitude. Their shallow reentry angles tend to degrade impact point accuracy unless they are terminally guided. Average heating and aerodynamic loads may be increased as a consequence of more time spent in endo-atmospheric flight. There is no clear demarcation between atmospheric and nonatmospheric flight because air density decreases exponentially with altitude. Nevertheless, above a certain altitude, typically 70 to 80 km, aerodynamic forces on the TBM are negligible because the dynamic pressure (one-half of the air density times velocity squared (Pdynamic = 1/2 Pair × V2) is low. Flight above this altitude is called exo-atmospheric flight, while flight at lower altitudes is called endo-atmospheric (or simply atmospheric) flight. Exo-atmospheric flight is unlikely for an impact range of less than 150 km unless the missile follows a lofted trajectory. For a greater impact range, the exo-atmospheric flight time varies from 0 to less than 20 min, while the endo-atmospheric flight time following reentry is 10 to 40 s. The boost phase may extend into the exo-atmospheric regime for an impact range of more than 300 km. Control forces for midcourse guidance correction can be provided by thrust during exo-atmospheric flight, while terminal guidance corrections can be effected by aerodynamic lift and drag control during endo-atmospheric flight. Sources for measuring guidance error—a necessary input to the guidance logic—include inertial measurement units; GPS or GLONASS; and terminal homing sensors, such as laser designation, optical or radar imaging and distance measurement, and radio stations or beacons. Each TBM has one or more warheads whose size and mass are dependent on the payload capability of the launch vehicle. Unitary warheads are likely to contain a high explosive—including the nuclear alternative—to damage or destroy the target, although a precisely guided inert penetrator could be considered for attacking a deeply buried asset. Multiple warheads, including independently targeted RVs or unguided submunitions, could carry explosives for damaging one or more targets or chemical or biological agents to attack personnel over a wide target area; for this reason, their effectiveness is less dependent on impact-point accuracy. Multiple warheads could be released shortly after boost, or they could be dispensed from a guided or unguided bus (carrier) vehicle following reentry. Even if TBM warheads are successfully engaged after boost, the remnants proceed on a ballistic path toward the vicinity of the target. If substantial destruction has been accomplished, the components or fragments are likely to have

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Page 33 a reduced ballistic coefficient, causing them to fall short of the target. For exo-atmospheric engagement, the parts could be further damaged by reentry heating, especially for longer range (and therefore higher velocity) missiles. Following endo-atmospheric intercept, the pieces—possibly including fully functioning submunitions—may still rain down on the target. Since atmospheric heating increases the temperature of the TBM warhead during boost and reentry, the warhead is detectable in both exo- and endo-atmospheric flight not only as a radar target but also as an infrared source. Countermeasures are intended to mask the position of the TBM warhead(s) from defensive sensors or to evade a defensive weapon. Spent boosters, debris fields (e.g., from a detonated booster that is not too close or too far), and deployed decoys may be difficult to discriminate from warheads, while the warhead itself could be cooled to make it less visible to infrared sensors. Given a field of incoming targets whose radar or infrared signatures are similar, defensive sensors must pick out the right targets for attack. The latter approach adds to the actual dispersion of the trajectory, and it increases the physical difficulty of killing the warhead, though TBM impact-point dispersion still could be contained by terminal guidance. The time to deployment for specific theater ballistic missiles is a critical issue. Near-term, mid-term, and long-term TBM threats must be considered, and there is a big distinction between an actual threat and a possible threat. As the window of concern lengthens, that is, as the planning horizon for TBM defense stretches out, the current (“actual”) becomes less interesting and the “possible” becomes more real, especially for technologies whose development can be kept from surveillance by intelligence. Therefore, programs for future defense against TBMs must take into account not only the characteristics of known threats but also the technologies that can be employed in response to an adversary's perception of our nation's defensive capabilities. Scuds and their derivatives, which thus far have accounted for the bulk of widely proliferated missiles, are generally inaccurate and do not separate spin or reorient their payloads. 2.3.2 Current Theater Ballistic Missile Threats For the present, it is sufficient to consider the TBMs discussed in NAIC-1031-0985-98 (4) as representative of current threats.1 While many of these missiles embody old and relatively rudimentary technology, the more sophisticated missiles that are replacing them in the inventories of supplier nations today 1 National Air Intelligence Center. 1998. “Ballistic and Cruise Missile Threat.” Wright-Patterson Air Force Base, Ohio. Available online at <http://sun00781.dn.net/irp/threat/missile/naic/index.html>.

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Page 34 can be expected to proliferate in the same way as the older systems did—by being exported. Figure 2.3, compiled from various unclassified sources, illustrates the major ballistic missile threats that the naval theater missile defense systems must contend with. The simplest TBMs are unguided beyond the boost phase, after which they follow ballistic trajectories toward their intended targets without trajectory corrections. They tend to be subject to large dispersions in impact point as a consequence of uncertain burnout conditions, physical modeling errors, tumbling and coning motions, and variations in wind and air density during endo-atmospheric flight. More sophisticated TBMs employ the following means to reduce reentry dispersion: Separation of the TBM warhead from the launch vehicle in order to effectively increase the ballistic coefficient (mass divided by drag coefficient and reference area), Reorientation of the RV to minimize the angle of attack (angle between the vehicle's axis of symmetry and the velocity vector) at reentry, and Provision of spin to the RV to provide gyroscopic stability and to cancel the trimmed lift force during and following reentry. Control forces for midcourse guidance correction can be provided by thrust during exo-atmospheric flight, while terminal guidance corrections can be effected by aerodynamic lift and drag control during endo-atmospheric flight. Sources for measuring guidance error—a necessary input to the guidance logic—include inertial measurement units, GPS or GLONASS, and terminal homing sensors, such as laser designation, optical or radar imaging and distance measurement, and radio stations or beacons. 2.3.3 Postulated Future Theater Ballistic Missile Threats Threat missiles will become more sophisticated in the coming years.2 Improved accuracy for warhead delivery and some form of countermeasures are almost certain to be incorporated into the TBMs that U.S. forces will face. The 2 (1) National Air Intelligence Center. 1998. “Ballistic and Cruise Missile Threat,” Wright-Patterson Air Force Base, Ohio. Available online at <http://sun00781.dn.net/irp/threat/missile/naic/index.html>; (2) Committee on Foreign Relations. 1999. “Foreign Missile Developments and the Ballistic Missile Threat to the United States Through 2015,” Hearings Before the Committee on Foreign Relations, U.S. Senate 106th Congress, First Session, U.S. Government Printing Office, Washington, D.C., April 15 and 20, May 4, 5, 13, 25, and 26, and September 16. Available online at <http://www.fas.org/spp/starwars/congress/1999_h/s106-339-8.htm>; (3) Commission to Assess the Ballistic Missile Threat to the United States. 1998. “Executive Summary of the Report of the

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Page 35 ~ enlarge ~ FIGURE 2.3 Tactical ballistic missile threats and their characteristics. SOURCE: Information extracted from (1) Cosby, Anthony W., “Protection from the Missile Threat,” (Unclassified) May 24, 2000, briefing to the committee, Program Executive Office, Air and Missile Defense, Arlington, Va.; (2) Patterson, CDR Sheila A., USN, “Navy Theater Wide TBMD Program (U),” (Classified) June 28, 2000, briefing to the committee, Program Executive Office, Theater Surface Combatants (PMS 452), Arlington, Va.; and (3) Rempt, RADM Rodney P. USN, “Naval Theater Missile Defense for the 21st Century,” (Unclassified) May 24, 2000, briefing to the committee, Office of the Deputy Assistant Secretary of the Navy for Theater Combat Systems, Washington, D.C.

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Page 36 threat indicators are already present. Newer TBMs incorporating accurate warhead delivery are in (or will soon enter) Russian and Chinese inventories. No one can state with certainty what specific countermeasures will be incorporated into threat TBMs within the next 5 to 20 years. However, the committee suggests that future threat TBMs, in response to the presence of defense systems, might incorporate some combination of the following capabilities so as to stress the capabilities of present and planned TBMD systems: RVs with reduced RCS, Flares and or IR chaff, Radio-frequency chaff, Escort jammers, Decoys and/or tethered objects, Shrouds to mask IR signatures, Coated boosters that are robust against laser attack, and Deceptive maneuvering. Some of these techniques (chaff, jammers, low-RCS RVs, shrouds, and so on) would stress the ability of our military's primary and secondary target acquisition sensors to detect and track the RV of interest. Others pose a sensor discrimination problem—for example, How does a TBMD system differentiate between an RV and a decoy? The committee believes that the situation in TBMD is much like the competition between ECM and ECCM techniques in the ASCMD arena. Although the foregoing potential countermeasures to a TBMD system are a significant concern, none of them is inherently immune to negation. The committee takes note of the vigorous debate that rages about exo-atmospheric discrimination and the ease of creating effective countermeasures. The Commission to Assess the Ballistic Missile Threat to the United States,” U.S. Government Printing Office, Washington, D.C., July 15. Available online at <http://www.fas.org/irp/threat/bmthreat.htm>; (4) Institute for Foreign Policy Analysis. 1997. “Exploring U.S. Missile Defense Requirements in 2010: What Are the Policy and Technology Challenges?” Washington, D.C., and Cambridge, Mass. Available online at <http://www.fas.org/spp/starwars/advocate/ifpa/>; (5) APS Forum on Physics and Society. 1994. Symposium on Theater Ballistic Missiles: What Is the Threat? What Can Be Done? American Physical Society, held in Washington, D.C., on April 18, published as Vol. 23, No. 4, October. Available online at <http://www.positron.aps.org/units/fps/aoct94.html>; (6) Director, Operational Test and Evaluation. 2000. “Navy Area Theater Ballistic Missile Defense (NATBMD),” DOT&E FY99 Annual Report to Congress, Department of Defense, Washington, D.C., February. Available online at <http://www.dote.osd.mil/reports/FY99/other/99natbmd.html >; and (7) Sessler, Andrew M., John M. Cornwall, Bob Dietz, Steve Fetter, Sherman Frankel, Richard L. Garwin, Kurt Gottfried, Lisbeth Gronlund, George N. Lewis, Theodore A. Postal, and David C. Wright. 2000. Countermeasures: A Technical Evaluation of the Operational Effectiveness of the Planned U.S. National Missile Defense System, MIT Security Studies Program, Union of Concerned Scientists, Cambridge, Mass., April. Available online at <http://www.ucsusa.org/security/CM_exec.html>.

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Page 37 contest between countermeasures and counter-countermeasures often hinges on particular idiosyncrasies or “tags” that can be exploited by one side or the other. Knowing how potential adversaries are exploiting their tags allows denying the tags. It is observed that those actually working on the defeat of countermeasures must of necessity keep silent, while those who raise issues of the difficulties of defeating countermeasures on the basis of so-called “physical first principles” arguments are not hampered by security issues. With insight into some of the ongoing restricted or classified work in this area, the committee would caution against the oversimplistic arguments often heard in the public rhetoric. While easily postulated, many countermeasures would be difficult to achieve. For example, many have proven to be difficult for U.S. engineers to incorporate into U.S. missiles. The committee wishes to emphasize that once deployed, a TBMD system must be upgraded periodically in response to observed threat indicators. Therefore, programs for future defense against TBM missiles must take into account not only the characteristics of known threats, but also the technologies that an adversary can employ in response to its perception of our defensive capabilities. Techniques to negate the countermeasure threats listed above may take several years to develop and implement. The committee believes that a robust and sustained R&D program to develop specific naval TMD upgrades to negate those techniques should be in place, and it addresses this point in Chapter 4. For TBMs with an ACM, the attacker has considerably more freedom in the design and deployment of penetration aids. If the RV's orientation can be controlled, the attacker can take advantage of RCS reduction, which significantly decreases the radar detection range and makes it much easier to use maskers such as chaff and jamming. Warhead maneuvers, intentional or not, increase the difficulty of intercept. Thus, although a tumbling TBM may be relatively easy to detect, hitting its warhead still may be a challenge. Relatively small thrust impulses applied during exo-atmospheric flight can induce spiraling motions in oblong or dumbbell-shaped bodies, while aerodynamic forces and moments produce spiraling or jinking of a streamlined body during reentry. The amplitude and frequency of such maneuvers can have a first-order effect on an interceptor's ability to sense and engage the warhead. Both deception and maneuvering can increase the uncertainty in estimates of the TBM trajectory. It must be recognized that both approaches add to the actual dispersion of the trajectory and that neither is compat-

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Page 38 ible with the accuracy needed for conventional TBM unitary warhead target damage objectives. With penalties in payload complexity and displacement of warhead volume and weight, terminal guidance and maneuver capability could be added to maintain acceptable impact-point dispersion. The emergence of that capability could be a threat indicator for these induced-motion types of counter-measure.