Page 39

Page 40

Joint doctrine has been promulgated to guide the conduct of air and missile defense in a theater;¹ however, the doctrine appears to presume that the theater has already been developed and that joint forces are in place. Other than to note that the same functions must be performed in undeveloped theaters, the joint doctrine is not helpful as a guide for expeditionary warfare. Although work is ongoing to evolve this doctrine at the Joint Theater Air and Missile Defense Organization (JTAMDO), the committee is not aware of any efforts to address the expeditionary warfare setting.²

Pending the development of doctrine to guide initial operations in an undeveloped theater, it falls to the Navy and Marine Corps to define the appropriate CONOPS. A CONOPS for expeditionary warfare in the littorals must address conflicting requirements for employment of operational assets and for control of offensive and defensive operations.

Concepts for conduct of the offense are amenable to preplanning to avoid conflict yet must remain flexible enough to support operations ashore by Marine Corps units that may become subject to variation because of real-time events. At the same time, and in the same area, defensive measures must be taken to defeat ballistic missile, cruise missile, and aircraft threats to forces in the area, both afloat and ashore.

The conduct of effective theater missile defense without disruption of and conflict with offensive measures is a very difficult task but a necessary one. However, several briefers told the committee that no concepts for coordinating offensive and defensive operations have been worked out. Developing such concepts is critical to the conduct of expeditionary warfare and deserves considerable effort. Such concepts are also necessary to a proper evaluation of the adequacy of theater missile defense programs.

Page 41

continues to become more difficult. This section discusses the effect of these factors on overall naval capabilities in ASCMD, OCMD, and TBMD.

Because antiship missiles in the hands of potential adversaries are so numerous, so sophisticated, and so widespread, and because every naval combatant becomes a target whenever it enters the theater and must defend itself well so as to be an asset rather than a liability, ASCMD must be the Navy's highest priority in TMD. While the Navy's current capabilities are inadequate against antiship cruise missiles and its funding plans insufficient to protect some classes of ships against them, the Service has in hand the fundamental framework for effective defense against foreseeable ASCM threats.

However, the Department of the Navy has not come to grips with the rapidly approaching necessity for overland cruise missile defense. In the future, adversaries will employ land-attack cruise missiles to deny U.S. forces needed access to ports and airfields in theaters of war. In the fundamental framework for an OCMD system, important elements are missing.

Because tactical ballistic missiles are widespread weapons of terror and potential mass destruction and are poised today to deny U.S. access into theater, the nation needs, as soon as possible, a capability that will provide TBMD for ports and airfields until assets of other Services are in place. The Navy's burgeoning TBMD capability divides into two parts: area- and theater-wide systems. There are clear differences in how well the two systems are progressing toward an effective operational capability. The NAD system promises robust local defense against the short- to medium-range TBMs prevalent today and appears to be progressing smoothly. The NTW system, on the other hand, is a demonstration, not an acquisition program. The activity lives year to year on funding provided through congressional plus-ups. Its initial capability, if indeed it becomes a funded acquisition program and the Program Executive Office for Theater Surface Combatants' current plans for it continue, will be limited by SPY-1 radar performance, which in some geographic scenarios is inadequate to provide the wide defensive coverage needed to deal with the threat of ever-longer-range TBMs. Furthermore, since adequate TBMD requires defense in depth, a Navy theaterwide capability will one day be required.

The next subsections delve further into the three mission areas (ASCMD, OCMD, and TBMD).

Page 42

area defense can help in important situations such as the close-escort protection of aircraft carriers.

Beginning with the AAW capstone requirements document (CRD) in 1996, the Navy has characterized the AAW performance of various ship classes in terms of a “probability of raid defeat,” whereby a raid is considered to be defeated if no threat missile penetrates the defense to hit the ship. The Navy defines the “probability of raid defeat” as a weighted sum of results against a specific raid (e.g., x low-altitude, low-observable, subsonic cruise missiles in y seconds). The CRD varies the x and y and the required “probability of raid defeat” by ship class. The committee takes no exception to the numbers in the CRD. The weightings are done across different classes of threat. A present-day low-altitude, low-observable, subsonic cruise missile is an example of class. The CRD does not specify the weightings. The Navy practice has been to give a heavy weight to the moderate cruise missile threats predominant today and much less weight to the more difficult threats, which are expected to emerge in the future or—if they already exist—are less numerous. This weighting tends to have a stronger effect on ship classes with less stringent requirements.

The Navy justifies the CRD requirements and the weighting practice as a way to allocate scarce funds, because it cannot afford to defend all ships equally. This is no doubt so. However, the committee fears that such a practice tends to obscure real vulnerabilities. The adversary will decide which ship to attack and with what missiles. The adversary may “win” (if, for example U.S. popular opinion turns against further action) by attacking and sinking a less-well-defended ship with the best cruise missile it can buy. Some ship classes will not have to operate for long periods of time in the littorals and be exposed to the full threat, but others will. The committee believes that any ship so exposed should have the benefit of the best defense the Navy can provide.

In the past, the air cover provided by Aegis ships was effective over a large area. Self-defense systems on some ship classes lagged in capability, but robust area defense gave Navy battle groups a good overall AAW capability. Today, with typical ship formations, the ability of one ship to defend another against some of the most dangerous antiship cruise missiles is almost nil, because the threats fly too low and too fast.

As the information presented to the committee by a number of Navy offices clearly shows, the Navy's overall current operational capabilities in antiship cruise missile defense are marginal and declining. In recognition of this, the Navy has been investing heavily in a number of new detection, control, and engagement systems and also in systems integration. When these new capabilities are fielded, antiship cruise missile defense will be markedly improved for the ships that receive them.

The committee is confident that the Navy has in hand the framework for antiship cruise missile defense. It consists of a combination of volume-search and horizon-search radars, well-automated fire control and doctrine that permits

Page 43

fast response through automated decision-making in high-threat situations, defensive missiles that match the sophistication of the threat, and a netted capability that enables distributed ships to fight as a coherent whole. These elements, fielded on the right ships in adequate numbers and in timely fashion, should enable the Navy to counter foreseeable antiship cruise missile threats. Ships that do not receive these upgraded capabilities will remain vulnerable. The current program of record does not fully deploy the new capabilities. For example, it appears that ships other than Aegis cruisers and destroyers will lack an adequate engagement capability. A launcher for the ESSM will not be available on these vessels, and they must depend on the rolling airframe missile (RAM). Nor does the current program of record field capabilities to cover all the potential electronic countermeasure threats. The committee believes that the Department of the Navy should prioritize funding so that every combatant that conducts sustained operations in contested littoral waters is adequately defended.

In summary, providing adequate defense against antiship cruise missiles will require reprioritization of funding, but the fundamental framework for ASCMD is there.

Page 44

ly, the airborne platform could control the weapon in flight (“forward pass”) or it could illuminate the target for semiactive homing by the weapon. Whichever concept is considered, major elements are missing. The Navy has no airborne platform capable of detecting a low-observable cruise missile overland. It has no ship-launched, actively guided air defense weapon. It has no airborne illumination capability.

The Department of the Navy is unprepared for a defense against land-attack cruise missiles and is not funding development to rectify the situation.

Page 45

(SM-3), with the original warhead/seeker stage replaced by a new third-stage motor and a HTK vehicle. With a much lighter final payload, the interceptor burnout velocity is much greater, permitting much longer fly-outs and thus much larger defended regions. To get the large coverage, the SM-3 is designed to intercept exo-atmospherically, which necessitates launching the interceptor much earlier in the threat missile trajectory. The weakest link in the proposed phase I NTW defense is the detection capability the Navy will obtain by evolutionary improvement of Aegis's SPY-1 radar. In geographic situations where the NTW ship can be placed near the TBM launch point, the protected region can be very large. However, in situations where the NTW ship is near the TBM aim point, the protected region can be very small, limited as it is by SPY-1's detection capability.

The committee believes that, certainly in NTW phase I and probably beyond, the Navy must devise concepts of operation that take advantage of detection assets not organic to the battle force. Forward-placed or space-based assets that detect TBMs early in flight would, through CEC or a similar link, enable midcourse control of NTW interceptors in order to greatly increase the size of the defended footprint in unfavorable geographies.

The Navy is considering a new generation of shipboard radars for TMD. Achieving adequate detection and discrimination for NTW ships will be a driving requirement. One concept combines an S-band volume-search radar (much more powerful than SPY-1) with an X-band radar for horizon-search against cruise missiles and for long-range TBM discrimination.

Because the severity of the near-term threat calls for fielding an NTW capability quickly, because many engineering challenges must be overcome to field even a limited NTW capability, and because the Navy will surely benefit considerably from experience gained in beginning to use the system as soon as possible, the Navy is considering fielding the so-called Block I NTW system. It is clear, however, that during the years it will take to field the system, the TBM threat will become even more severe, especially in the use of penetration aids, partly in response to the advent of the NTW system itself. The Navy's informal plans call for a Block II capability against a more severe threat, but the R&D to solve the challenges Block II will face is dragging. The committee also believes that in some geographic scenarios, the NTW system may ultimately need to depend on detection capabilities not organic to the ship in order to achieve wide defensive coverage.

Page 46

Page 47

formance is not a function of frequency. However, since power and aperture are generally cheaper at low frequencies, search radars tend to be designed to operate at lower frequencies as appropriate to U.S. radars.

The threat generally consists of a number of objects—reentry vehicle (RV), debris, deliberate decoys, discarded booster stages, and so on—each of which has an RCS value. Thus, each will be detected at a different range. The booster will probably be the first thing to be detected by a surface radar. It may be detected either in autonomous search or in directed search as a result of cueing by an up-range radar or other detection sensor. After booster burnout, radar data can provide the basis for a good estimate of the booster impact point. For most TBM systems, the booster impact will be close to the RV impact point. Depending on the specific TBM system, the RV may be known to stay relatively close to the booster. This information permits the launch of an interceptor toward the predicted location of the booster. When the interceptor approaches the booster-RV pair, the location of the RV will be resolved by either the surface radar or the interceptor seeker in time to divert the interceptor and kill the RV.

The radar can also do a local search in the vicinity of the booster looking for smaller targets. Since the radar energy can be concentrated in a smaller region, the detection range for these smaller targets can be much greater (often by a factor of 2 or more) than that with autonomous search. Since the radar beam width is narrower at higher frequencies (for fixed aperture size), cued search is generally more effective at high frequency. This is the case for discrimination also. Exo-atmospheric discrimination of both incidental debris and deliberate countermeasures generally relies on looking at the time history of the target RCS or a range- and/or Doppler-resolved RCS map of the target. This requires enough resolution so that different parts of the target appear in different range or Doppler resolution cells. Such resolution is available only at frequencies of S-, C-, or X-band, with the finest resolution at X-band. The use of higher frequencies is limited by attenuation in heavy rain or dense clouds if the radar is oriented toward the horizon and propagates over long distances. For TBMD systems, the radar is generally oriented to search high angles of elevation. In such circumstances the distance that the beam propagates through moisture-laden regions is relatively short. Thus, rain attenuation in TBMD radars may be tolerable at X-band frequencies but not at higher frequencies. For long-range AAW, the radar is designed to search at low elevation angles, and X-band suffers too much attenuation for practical designs. That is why radars with a long-range AAW mission, such as SPY-1 or Patriot, operate at S- or C-band frequencies.

The final function of the surface radar is to hand over the identified target (or threat volume) to the missile seeker. There is a premium for making this handover as accurately as possible for two distinct reasons. First, the requirements on seeker acquisition range are a strong function of the handover accuracy, as is discussed in the section on weapons, below. Second, even if the radar can identify the RV uniquely, if there are other nearby targets, the seeker may

Page 48

not be able to discriminate the RV from another target because its resolution cell has a shape different from that of the radar uncertainty volume.

Ground or aircraft radars generally measure range very accurately and measure angle fairly crudely. The radar uncertainty volume is pancake-shaped, with the diameter of the pancake generally hundreds of times larger than the thickness. A ground or airborne radar forms one of these pancakes for each target in the vicinity of the RV and can pass this information—called a target object map (TOM)—to the interceptor. When the IR sensor on the interceptor looks at these pancakes, it can distinguish different angular positions but does not measure range. Unless the interceptor sensor has a radar capability in addition to an IR capability, the uncertainty region of an interceptor's IR sensor will be conical. If the seeker cone for a particular target cuts through more than one radar pancake, the seeker may not be able to uniquely associate the targets it detects within its cone of uncertainty with one of the radar targets and may, as a result, home on the wrong object. The performance of this function depends on the spacing of threat objects relative to the radar pancake diameter. The radar uncertainty volume is a strong function of radar antenna design and frequency, with higher frequency radars providing narrower beams and higher signal-to-noise ratios, resulting in much more accurate handovers. This handover to the interceptor is an essential fire control function, and the critical need for accuracy is the reason that fire control radars are generally at the highest frequency to propagate in all kinds of weather.

A number of different radars (and other sensors) have been considered for use in ship-based TBMD systems. The capabilities of the current SPY-1 radar and potential upgrades are assessed first, those of other TBMD radars such as THAAD and Patriot are assessed next, those of National sensors, such as the Defense Satellite Program (DSP) and the SBIRS, are assessed last.

The NAD system is a straightforward upgrade of the Aegis AAW system that incorporates modifications to the interceptor, the radar, and the software to permit attacking ballistic targets late in reentry. It does not require very long range or sophisticated discrimination, and the current SPY-1 is suitable for this job.

The NTW system would enable a completely new mission. To get the large coverage, the NTW interceptor (SM-3) is designed to intercept exo-atmospherically, which necessitates launching the interceptor much earlier in the threat missile trajectory. The RV must be detected and identified earlier and at relatively long ranges. The current SPY-1 does not have the sensitivity to detect small RVs at the ranges needed to support the fly-out capability of the SM-3 and must depend on another SPY-equipped ship or other radar to provide track information at longer ranges.

A number of approaches to solving this problem exist, and all of them are being considered. The long-term solution is to develop a new or upgraded radar with sufficient sensitivity. Analysis indicates that such a capability will require an improvement in detection range by at least a factor of 2, which translates into

Page 49

an improvement in sensitivity by a factor of 16 (or 12 dB). The committee was told that the Navy is conducting several “radar roadmap” studies to coordinate radar developments for both NTW and NAD. Some of the candidates for the NTW (Block II) radar include a separate X-band TBMD-only radar similar to the THAAD radar and an S-band or S- and C-band radar to do both TBMD and AAW. The radar detection range depends on the target RCS, and a radar that is adequate for one particular RCS level may be inadequate or overdesigned for a smaller or larger target.

The development and acquisition of a new radar will take a number of years. In the meantime, the NTW system can get some useful capability out of the current SPY-1 radar by taking advantage of ship deployment flexibility in some scenarios and of good knowledge of the threat TBMs in other scenarios. In several important cases (e.g., near the coast of North Korea), the NTW ship could be sited near the TBM launch point and could detect a large RCS booster at relatively short range. It could then do a cued search for the RV before it got out of range. The SM-3 has enough velocity to catch many TBMs even in a near-tail-chase geometry. If the ship cannot get close enough to the launch point to be able to detect the RV, it could use its knowledge of the TBM geometry to launch the interceptor toward the booster and have the seeker acquire the RV in time to divert. However, where the ship must be deployed downrange from the impact point, radar detection of the RV generally occurs too late to conduct a successful intercept. An upgraded radar is required for these cases.

Figure 3.1 and Figure 3.2 show how the requirements for radar range and interceptor velocity can be traded off for both terminal-phase and ascent-phase operation using an exo-atmospheric interceptor.

In this example, the incoming missile's reentry angle is assumed at 45 deg, its altitude at burnout is assumed at 75 km, and its velocity is assumed at 2.5 km/s. This analysis is highly simplified, using flat-earth and straight-line, constant-speed trajectories for both target and interceptor. Although the numerical results are only approximate, the example shows the difference in dependencies on radar range and interceptor velocity between terminal-phase defense and ascentphase defense.

In terminal defense operation, the forward footprint distance is a measure of coverage (e.g., the distance that the impact point is forward of the defense site). The results show that the coverage can be increased by increasing the radar range to give the interceptor more time to fly out or by increasing the interceptor speed to let it fly further in the same time. The curve for zero footprint corresponds to self-defense.

In ascent-phase operation, the parameter of the curves is the standoff distance, the distance (downrange) from the TBM launch point to the defense site. The curves differ significantly from those for terminal operation. If the interceptor is faster than the target (2.5 km/s in Figure 3.2 ), a fairly short-range radar may be adequate. It can detect booster burnout, determine the intercept point,

Page 50

~ enlarge ~
FIGURE 3.1 Trade-offs between radar range and interceptor velocity in a terminal-phase engagement.

and send the interceptor on its way. The intercept point will also be within radar coverage. However, as the interceptor speed decreases, the intercept point gets much further away, and eventually the interceptor cannot catch the target. There is a best location for the defense site—in this case, it is at a standoff of about 150 km (for a 600-km trajectory). If the defense site is closer, the intercept becomes too much of a tail chase, and if the defense site is further away, the interceptor must fly too high to reach the target.

Page 51

~ enlarge ~
FIGURE 3.2 Trade-offs between radar range and interceptor velocity in an ascent-phase engagement.

A final approach to fire control for NTW is to launch the SM-3 based on data from external sensors. These might include up-range Aegis ships, an uprange land-based radar such as a THAAD, or a space-based system such as SBIRS-low. In some scenarios, these sensors could provide the accuracy needed for fire control, but significant BMC3 changes would be required to exploit this capability. The THAAD radar has the sensitivity comparable to that needed for NTW Block II.

Page 52

Page 53

will provide excellent tactical warning and attack assessment and cueing data directly to forces in the field as well as to the National Command Authority.

This system is currently well along in development and the first two spacecraft are scheduled to be delivered within the next 2 years. The current program is planned to deliver a complete constellation on orbit by approximately 2007—the time frame when naval TMD will begin entering the fleet.

The SBIRS-low, while not yet approved for development, is conceptually designed to operate in the visible and long-wavelength infrared (8 to 14 µm) spectra, looking at targets against the cold space background. The task of SBIRS-low would be to provide midcourse tracking of ballistic missiles in flight and hand off the target(s) to a terminal defense system. With its multispectral sensors it could, in principle, provide some discrimination of objects in midcourse.

As a consequence of the decision not to proceed with the future early warning system (FEWS), the SBIRS-high acquisition design parameters were changed to include detection of intermediate-range ballistic missiles (IRBMs) and short-range ballistic missiles (SRBMs). To accomplish a higher scan rate with the greater sensitivity needed to detect and track IRBMs and SRBMs, a two-dimensional, focal-plane array was added along with another detection band at 4.3 µm.

Discoverer II (now a canceled program) was intended in part to be a space-based version of the airborne joint surveillance and target attack radar system (JSTARS). It was designed to function as a ground moving target indication (GMTI) radar, and it would have been capable of providing synthetic aperture radar (SAR) imagery. Various versions of Discoverer II were planned to have between 24 and 57 satellites to provide timely and ubiquitous worldwide coverage.

No space-based analogue of the AWACS AMTI radar that would be appropriate to the problem of ballistic and cruise missile defense exists as a program of record. Although the committee is reasonably confident that the development of such a capability would be technologically feasible within the next 10 to 20 years, questions of affordability exist. Thus, within the next 10 to 20 years, there is relatively little prospect that satellite AMTI radars will become a major contributor to the Navy's missile defense systems.

Page 54

appears to be an important part of the Marine Corps' CLAWS point defense concept, along with air surveillance and fire control radar for employing CLAWS.

CEC development itself appears to be proceeding without serious problems. Exercises in Hawaii demonstrated both the concept of operations and the technical achievements required to deploy CEC effectively. The required technology appears to be well in hand, and there do not appear to be any significant technical risks remaining at this point that would delay planned fleet introduction. The primary risks now appear to be inadequate funding for retrofitting the capability on all the firing platforms that could bring missiles to bear on the various air and missile threats to littoral operations.

The prognosis for the development of an airborne sensor node is a different story altogether. The Navy is currently basing its OCMD concept of operations on an upgraded E-2C to provide the airborne node. The E-2C is the Navy's 1960s-vintage solution to its air surveillance requirements for blue-water operations. Its air-surveillance radar has been improved over the years. The current APS-145 radar, which incorporates space-time adaptive processing (STAP), has more near-land and overland clutter rejection capability than the earlier APS-138 radar. However, the overland performance of the APS-145 radar is not adequate to meet the airborne air surveillance requirements for OCMD. The Navy's proposed solution is a hybrid version of the APS-145, which would employ a rotating, electronically scanned array called the ADS-18. Although it is designed to be placed on an E-2C, there is no inherent reason why it cannot be placed on another aircraft such as a militarized 737, C-17, or P-3. Someday a sea-based UAV may be a reasonable candidate for such a radar.

The technology appears to be in hand to develop such a radar, as well as an alternative nonrotating, scanned array with 360-deg coverage that would fit within the envelope of the existing APS-145 radar TRAC-A antenna radome. However, the lead time required to develop and field it will be long. The Navy's planned ADS-18 RMP for developing even the hybrid solution appears to be unaffordable for the Navy at this time; currently the program is not funded. Given the critical importance of an airborne air surveillance node for the achievement of a credible littoral TMD capability, the committee believes that this is a major issue that must be addressed. If funding to support the E-2C RMP is not available, alternative approaches to providing an elevated sensor for OCMD should be considered.

The committee also believes that the E-2C platform's suitability for littoral warfare is open to question. In blue-water operations, its positioning relative to combat air patrol (CAP) fighters and missile-equipped ships can afford it good protection. However, in littoral operations, where the objective is to provide air surveillance for TMD support of troops ashore, it would be more vulnerable to attack by hostile surface-to-air missiles. Operational commanders would need to choose between a standoff distance for necessary survivability and overland radar

Page 55

coverage. During blue-water operations, missile-equipped ships can be positioned to provide continuous air surveillance to cover the battle group when the E-2C is not airborne. In littoral operations, once forces are ashore, the provision of airborne CEC and radar surveillance coverage becomes a much more stressing 24 hours per day, 7 days a week requirement.

Other tactical considerations come into play as well. Owing to its size, which is driven by shipboard launch and recovery constraints, the E-2C has space for only three system operators to do a significant portion of the job done on an AWACS with a crew of about 21. Automation currently offers E-2C system operators some workload relief. However, they are required to work much closer to the overload point in a much more fatiguing environment. This and the more complex, intensive, and dynamic nature of littoral air warfare and missile defense will push operators closer to, if not beyond, their workload limits. The immediate effects on the campaign of this, or the loss of the onboard CEC or radar system, or the platform itself, for whatever reason, must be taken into account, especially with troops ashore. Also, the optimal tactical positioning of the air node for CEC and for air surveillance will probably be different.

Operational availability of the E-2C platform and its transit time to and from station, as a percentage of its total mission time, are other considerations that must be taken into account. The E-2C has 4-hour legs, and the Navy's E-2Cs currently do not have an air-refueling capability. These considerations must be factored into the equation for the number of CEC-equipped RMP E-2Cs that will have to be procured to support the Department of the Navy's TMD concept of operations.

Taken together, these considerations suggest that the Navy's air node platform solution needs to be rethought. One approach might be a CONOPS that routinely depends on the use of the Air Force's AWACS as the elevated AMTI sensor. Another approach might be to employ a sea-based version of the Army's JLENS. The Army claims that the JLENS lift platform can stay aloft in 150-knot winds. If so, the platform can be towed by a surface ship. Unfortunately, the footprint of the JLENS is sufficiently large that it would probably require a dedicated hull for its deployment. Alternatively, emerging long-endurance, fixed- and rotary-wing UAV concepts may offer more affordable and cost-effective air node solutions for CEC and lower-risk solutions for airborne air surveillance in littoral warfare than the E-2C.

Although AWACS, JLENS, and the proposed new E-2C radar would all provide excellent AMTI capabilities against current overland cruise missile threats, their future performance might be degraded by two factors. The first of these would be the introduction of low-RCS cruise missiles. There are limitations in the power aperture gains that can be achieved by such radars. Unless new approaches are adopted, the advantage will eventually shift to cruise missiles. The other problem is that to ensure the survival of an elevated radiating platform, it will generally be necessary to position it at significant distances from

Page 56

the local area of conflict. Since radar performance degrades as the fourth power of the range, the performance of elevated sensors will degrade as their safety is assured by keeping them remote from the area of conflict.

One approach might be to make the elevated node function as a multistatic rather than a monostatic radar. Future variants of the new E-2C radar, JLENS, or the AWACS might function as transmitters in a multistatic system. A multiplicity of UAVs might serve as receivers. Since the UAV receivers might operate relatively close to the area of conflict, there would be significant recovery of propagation loss. This would allow targets with smaller cross sections to be detected. The committee recognizes that operating such a system would be significantly more complex than operating a conventional monostatic radar. However, multistatic radars can detect target glints and can exploit the fact that low-observable cruise missiles are not low-observable from all viewing angles. Thus, multistatic radars offer the possibility of countering further reductions in the nose-on RCS values of cruise missiles.

Finding a more affordable and cost-effective UAV alternative will require rethinking the radar solution. As an example, repartitioning the radar system into a ship-based package and an airborne package through the application of new technologies would reduce the size, weight, and cost. This lower cost would make larger numbers of UAVs more affordable and would provide the operational commander with more reserve capability and lessen the impact of combat losses on the campaign. Since the Navy has not yet funded the E-2C RMP, an examination of other options for the elevated sensor node appears to be both timely and appropriate. If both the E-2C and UAV options turn out to be infeasible, then the Navy and Marine Corps should consider developing a joint CONOPS with the Air Force that is based on the routine use of AWACS to ensure the feasibility of providing OCMD for Marine Corps expeditionary forces ashore.

Based on the foregoing considerations, the committee has concluded that the Navy's inability to fund the introduction of the new AMTI radar with the ADS-18 antenna into the E-2C creates a critical deficiency in its approach to the development of a credible OCMD capability by 2015. The committee also believes that the Department of the Navy may have better options than the E-2C for an airborne CEC and radar surveillance node for littoral warfare.

Although an elevated AMTI radar would be the sensor of choice for OCMD, the committee recognizes that such a sensor may not be affordable. The committee also realizes that although a ground-based radar (GBR) is not an optimized sensor for OCMD operations, a GBR can provide significant radar surveillance capabilities. The Marine Corps actually owns eight TPS-59 radars, which are excellent GBRs that could make a major contribution to OCMD.

Unfortunately, the Marines believe that the TPS-59 is too large for tactical deployments because it consumes too much valuable space and volume on current amphibious ships. Thus, the Marine Corps concept is that the TPS-59 will be flown into theater once an airfield that will accommodate C-5 or C-17 aircraft

Page 57

has been secured. The committee believes there could be scenarios in which no airfield is available in the area of operations that could accommodate the arrival of a TPS-59.

The near-term lack of any kind of effective OCMD sensor should dictate an examination of alternatives. The recent creation of Marine Corps expeditionary brigades (MEBs), which are designed in part to marry up with one of the three MPF squadrons that are forward-deployed around the world, provide such an alternative. The MPF ships have the capability to transport a TPS-59 radar and its associated equipment and can be routinely moved toward developing areas of crisis. The MEB's air combat element (ACE), which includes air defense units, could marry up with the TPS-59 and the MPF squadron in the area of operations for immediate employment ashore.

If the Marine Corps were to place one TPS-59 in two of the three MPF squadrons, then a TBM/OCMD sensor could be moved ashore early in a deployment if required, and it would provide good capabilities for both the Navy units afloat and the Marine Corps units ashore. While the TPS-59 is not a fully satisfactory alternative to an elevated AMTI radar in OCMD engagements, it is significantly better than no OCMD sensor at all. Although the committee acknowledges the limitations of a TPS-59 as an OCMD sensor, it points out that when used in a TBMD role, its performance should be quite credible.

Page 58

tion angles. The same is true for the Mk 23 TAS search radars carried on DD-963-class destroyers. Even Aegis's SPY-1 (S-band, three-dimensional, phased-array) radar is taxed against such threats. Sea-skimming flight raises the issue of anomalous electromagnetic propagation due to temperature and humidity variation near the sea surface and also can cause strong multipath fades. These environmental effects can greatly compound the detection problem. Another difficulty results from land background clutter that is inherent in operation in the littorals. Aegis's SPY-1 radar was developed for use in open ocean and is not as effective when operated in the presence of clutter from land background.

The Navy is developing four systems that together will bring a dramatic improvement in detection performance against antiship cruise missiles. The first is MFR, which is planned to provide a horizon search capability greatly exceeding that of any other radar in the fleet today. The MFR is planned for a number of future ship classes, including future aircraft carriers, DD-21, and an LPD-17 upgrade. The MFR (X-band, three-dimensional, phased-array) will not suffer as much as lower frequency (e.g., S-band) radars do from multipath and anomalous propagation effects. MFR will also have good performance near land as well as in open ocean. As an interim measure, to improve low elevation detection capability, the Navy is introducing the SPQ-9B (X-band, two-dimensional, rotating) on some near-term new production ships (carriers and Aegis ships and the LPD-17). It intends to backfit the SPQ-9B on some amphibious ships. At present, there is no plan to switch Aegis new production ships over to the MFR. The committee believes the Navy should reexamine this decision.

The second system that will markedly improve the Navy's capability to detect airborne threats is the SPY-1D(V) radar upgrade on Aegis ships. The upgrade will increase transmitter power, reduce transmitter noise, and possess a number of features to improve its capability against a land background. Signal processing improvements introduced with the SPY-1D(V) upgrade can be backfitted into older versions of SPY-1B and SPY-1D and significantly improve their performance. In self-defense against high-speed, low-observable threats, a cue from CEC (discussed below) or the SPQ-9B can enable the SPY-1D(V) (or SPY-B/D with signal processing upgrade) to detect at longer range and permit weapon employment in some cases where, absent a cue, no shot would be possible.

A third system that will improve detection of airborne threats is a new volume search radar (VSR) to replace the SPS-48 and SPS-49. VSR is being developed primarily for better reliability and economy. It will also provide improved performance against airborne threats above the horizon. Like the MFR, it is planned for future carriers and for the LPD-17 and DD-21 ship classes.

The fourth system that will enhance detection performance against airborne threats is CEC, whose composite tracking capability will take advantage of geometric and frequency diversity to detect and track low-observable vehicles. In CEC, a track is initiated when an individual ship detects an object on multiple

Page 59

radar scans. (This is conventional, except that more than one of the individual ship's radars can contribute to the multiple detections.) The ship initiating the track puts it on the CEC net, and all participants in the net then know the track. Thereafter, any detection by any participant, even if short in duration, is associated with that track. Tests demonstrate that the ability to view a low-observable target from various angles with radars of different frequencies adds significantly to the robustness of the track.

From time to time, infrared search-and-track systems have been demonstrated and proposed for installation on surface ships, especially to enhance low-elevation detection, but they have never reached operational status, primarily owing to their weather limitations.

It is worthwhile at this point to make some observations about the relative importance of area defense as opposed to self (point) defense. First, the SPY-1D(V) upgrade scheduled for introduction with Aegis baseline 7 in 2003 will significantly improve Aegis's area coverage against many threats. Second, cues from CEC can provide additional benefit. In the final analysis, however, even with SPY-1D(V) and cues from CEC, Aegis ships are reduced to near point-defense capability against some low-altitude threats. Therefore detection improvements planned for ship classes other than Aegis are important for their survivability in-theater.

3.2.1.5 Sensors for Air-to-Air Combat

For more than half a century, carrier-based fighter aircraft have provided the outer layer of a battle force's defense in depth and escorted aircraft penetrating inland. The current and projected future naval mission—to operate in the littorals and influence events ashore—requires air superiority. Although the technical capabilities of our potential adversaries' tactical aircraft and air-to-air missiles are improving, largely because of Russia's marketing efforts, with few exceptions their air forces are small, and a direct, large-scale confrontation with them is unlikely. However, an air-to-air engagement at the beginning of a conflict could be a logical part of a weaker adversary's response to our naval presence. Early in a conflict an enemy aircraft may have an opportunity to defeat a U.S. Navy or Marine Corps fighter because of asymmetric rules of engagement. The adversary may have permission to fire at will while our fighters are constrained to fire only when positive identification as hostile has been established. Although radars on U.S. naval fighters have greater detection range than those on adversary aircraft and our missiles and our stealth may add to this detection range advantage, freedom to fire at will may enable the adversary to shoot first. Given the political reality that U.S. fighters will remain under strict constraints to limit fratricide and collateral damage, the driving requirement is to achieve combat identification at long range. This is a difficult problem that will probably be

Page 60

solved only by a combination of approaches, one of which is improvements to aircraft radars to allow RF imaging. Some others are track-from-base, SIGINT, and good tracking and data fusion.

E-2C aircraft have for decades provided wide-area air surveillance for carrier battle groups. They continue to be reasonably effective in this role, but the aircraft is looked on to carry out new missions in the future, as discussed in Section 3.2.13, “Sensors for Overland Cruise Missile Defense.”

Vectored toward an enemy aircraft by the E-2C, an F-14 aircraft can detect (but not identify) the adversary at long range with its powerful AWG-9 radar. The F-18, including the new E/F versions currently becoming operational, carries a lesser radar. The airborne electronically scanned array (AESA) radar upgrade (APG-79) planned as a P3I program for the F/A-18E/F will significantly improve aircraft capabilities, especially against multiple targets, in response to cueing and through RCS reduction.

Page 61

Navy had no acquisition programs for lasers or directed-energy weapons. Early concepts for BMD weapons envisaged the use of nuclear warheads on the defensive missile. For a wide variety of well-founded reasons, all such concepts have been abandoned by the United States, and with the exception of laser weapons, contemporary BMD weapons are designed as kinetic-energy weapons (KEWs) or use nonnuclear warheads to negate the target. BMD weapons today engage their targets outside the atmosphere, very high within the atmosphere, or deep within the atmosphere with miss distances small enough to allow fragmentation warheads to achieve lethal damage. Simply put, the problem in using a HTK weapon is to hit a bullet with a bullet. This problem is very difficult, with miss distance requirements less than the radius of the interceptor.

To achieve kinetic kill or the very small miss distances necessary, the weapons in a TBMD system must fly out and acquire, identify, home on an incoming RV coming close enough to fuze (or, in the case of kinetic kill, to collide with the RV), and have high warhead effectiveness. This section focuses on IR homing interceptors such as the SM-2 Block IVA and the SM-3 Blocks I and II. The SM-2 Block IVA is designed to intercept both lower atmosphere air-breathing threats and shorter-range tactical ballistic missiles. It engages tactical ballistic missiles in a deep reentry regime and employs a mid-wavelength infrared (MWIR) seeker, aerodynamic maneuverability, and a fragmentation warhead that is designed to be effective against aircraft and RVs. Because it must engage at low altitude, the SM-2 by necessity has a relatively small defense coverage. The SM-3 operates exo-atmospherically, offering, in principle, a very large defended area. It has the ability to destroy targets before they can maneuver significantly. The price for this capability is the need to deal with lightweight countermeasures that the atmosphere filters out for the lower-tier SM-2. SM-3 employs a kill stage with a long-wavelength infrared (LWIR) seeker, uses thrusters to maneuver, and makes use of the large kinetic energy of a direct hit to achieve a kill.

As discussed in the overview section of this chapter (Section 3.1), a surface radar or other sensor must tell the interceptor where to go. The interceptor needs a burnout velocity (V_bo) sufficient to achieve a collision point on the trajectory of the RV in the available time. There is a trade-off among the interceptor size/ weight, the payload weight, and V_bo. Both the SM-2 and SM-3 must fit in a vertical launch system (VLS) tube and are thus comparable in size. They embody different trades between payload and V_bo. The SM-2 has a modest V_bo but delivers a heavy payload containing the IR seeker, a semiactive radar seeker, and a substantial fragmentation warhead. It operates in the atmosphere and has significant aerodynamic maneuver capability. The SM-3 carries only a small payload consisting of an LWIR seeker together with navigation and divert systems. An extra propulsion stage has been added to give a much higher V_bo and some radar-directed divert capability. The terminal stage or kill vehicle of the SM-3 operates exo-atmospherically and its maneuver capability is obtained by the use of thrusters.

Page 62

~ enlarge ~
FIGURE 3.3 Kill vehicle look and kinematics constraints versus cueing error volumes (two-dimensional slice)—handover volume effects.

Figure 3.3 illustrates the nature of the progressive handover from cueing sensor to radar to the interceptor. Section 3.1 describes the alternatives and issues involved in detection and handover accuracy, from the early warning sensors to the radar directing the interceptor.

Once the interceptor gets to the vicinity of the target, the seeker must search the radar handover volume, detect all credible targets, identify the RV, and divert toward it. The seeker must have a field of regard and detection range large enough to see an RV anywhere in the handover volume soon enough for the interceptor to divert to and home on the RV with the propulsive or aerodynamic energy available. If the radar can identify the RV from debris or deliberate decoys, the radar's tracking accuracy will determine the handover volume. If the radar cannot identify the RV, the handover volume will be limited by how far the RV could be from a known object such as the booster. If the seeker field of view can cover the handover volume, the detection range is limited only by the seeker sensitivity. If the field of view is smaller than the handover volume, the seeker must scan the volume (for example, using step-stare modes), which will delay detection. The size of the seeker field of view represents a trade-off between the pixel resolution (needed for sensitivity and homing accuracy) and the number of pixels in the focal plane array.

Page 63

Once the seeker acquires objects in the handover volume, it must decide which one is the RV. Associating its view of the threat with the radar view may do this. If the radar hands over only one object, the seeker looks for the target closest to this point in space. If the radar hands over multiple objects, the seeker tries to match the pattern of objects (TOM). It then homes on the object that the radar identified as the RV. If the radar is not confident of the identification of the RV, or if the threat cloud density precludes confident association, the seeker must do target identification on its own. For a one-color IR seeker, identification might rely on target intensity and scintillation and spatial correlation with hand-over data. If a two-color IR seeker is available, it will allow inferring the target temperature and emissivity-area product, which provides more powerful discrimination capability. The RV identification process takes some time, which lessens the remaining time (given by the range-to-go divided by the closing velocity) available for divert and homing. The endo-atmospheric interceptor has aerodynamic limits on g's and total divert versus slowdown constraints, and the exo-atmospheric interceptor divert motors have limited g's and total divert velocity. They and the time remaining to closest approach determine how far the RV can be from the center of the handover volume.

After diverting toward the RV, the seeker angle accuracy and the interceptor response time must be such that the resulting miss distance is within the interceptor's lethal radius. For interceptors with warheads, this may be a few meters, but for HTK interceptors, it is a few centimeters. In particular, the HTK lethal radius is smaller than the target, so the interceptor must hit a particular aim point on the target. This is accomplished in the last second when the seeker resolves the target, selects the correct aim point on the target image, and makes a final divert toward that aim point. The feasibility of both of these intercept methods has been demonstrated in BMD research and development programs during the last 20 years.

Page 64

uncovered. Argon gas is blown over the dome face to separate the aerodynamic shock wave and keep the dome from overheating. The missile operates its semiactive RF seeker for use as a backup if necessary.

While the atmosphere will strip away much of the lighter debris that can surround a TBM warhead, the presence of heavier objects such as the missile propulsion tank or attitude control module can complicate the discrimination task.

The Navy plans to rely on a relatively simple method for handing over the target from the ship radar to the missile. The radar will send to the missile the expected angular position, angular rate, and something akin to the angular acceleration of just one object, the object the ship radar identifies as the target (the part of the TBM complex carrying the warhead). This is in contrast to other U.S. systems, in which the tracking radar transmits a TOM to the missile for handover. The committee was presented data showing that the simple method is proving reliable.

Fuzing is accomplished via an algorithm that combines IR seeker inputs with those from the new adjunct microwave RF ranging sensor. The missile's air target RF fuze is available as a backup.

Among the area TBMD engagement challenges is that of killing a TBM that is “coning,” whether inadvertently or deliberately. To inflict sufficient mission-terminating damage, the SM-2 Block IVA be must guided to a location on the target very near its warhead. Therefore target maneuvers of any sort will complicate terminal guidance. SM-2 Block IVA will intercept its target well within the atmosphere, when aerodynamically induced target maneuvers are possible. To counter the helical maneuver effects of coning, SM-2 Block IVA plans to observe the motion of the target, characterize it, and employ a predictive algorithm to estimate the target warhead location at time of intercept.

The SM-2 Block IVA has an explosive warhead designed to be effective in the atmosphere against both air vehicles and missiles.

Taken together, the new elements of SM-2 Block IVA appear to the committee to constitute a moderate development risk, as indeed does the whole Navy area system concept.

Page 65

Second, the Navy is using the material rhenium to build the piping necessary to divert the gases. The rhenium must be handled at the high temperatures associated with the solid propellant exhaust and is proving to be a difficult material with which to build reliable plumbing.

By designing the SM-3 only for exo-atmospheric operation, the design can be simpler (and lighter) than the design of an interceptor such as THAAD, which is designed to operate both outside and high within the atmosphere. However, the design also places a number of restrictions on operation in an NTW scenario. Some short-range TBMs, including the SS-21 and Scuds, which have ranges less than 400 km, never get high enough for the SM-3 to engage them. To engage above the atmosphere, intercepts must take place well uprange of the TBM impact point. This significantly limits the coverage in descent-phase engagements, primarily because of the limitations of the radar.

The committee was not presented with detailed analysis of the NTW system except for ascent-phase engagements. Many if not most of the situations the naval forces will face in expeditionary operations will require defense of forces against threats in trajectory descent phase coming from inshore. These engagements are more stressing, as the following discussion illustrates. Figure 3.4

~ enlarge ~
FIGURE 3.4 Self-defense engagement example.

Page 66

shows a sample graphical engagement analysis for an interceptor with characteristics similar to those of the SM-3 against an intermediate-range TBM. It serves to illustrate the issues arising from the engagement constraints imposed by the various functions that must be fulfilled for a successful intercept. In Figure 3.4, the curved contours represent shortest fly-out time contours for the interceptor, determined by flying out many different trajectory shapes including energy management. The crosses descending from the upper right to the lower left are time ticks along the threat trajectory, and the solid curve from the origin is the interceptor trajectory for the engagement shown.

In this example, it is assumed that a forward sensor like SBIRS-high detects the launch of the threat and tracks it through burnout of the main propulsion. As previously mentioned, the SBIRS frame rate allows determination of azimuth and velocity with sufficient accuracy to project a handover volume forward in time suitable to cue the shipboard radar into a very reduced search volume. It is assumed that the radar begins tracking the target complex when it can see the larger-cross-section booster tank and can commit an interceptor any time after it has the complex in track and has designated the RV. It is assumed here that when the radar has detected and tracked the RV itself for 10 s, it is designated as a target to be engaged. The detection of the RV is assumed to occur at the arc of dots labeled “detection,” which for the case shown is arbitrarily chosen to be 300 km from the ship's location at the origin. It is further assumed that the interceptor is launched at the optimum time such that it reaches 80 km (where dynamic pressure is effectively zero) just as the ship's radar designates the RV as a target. This allows the interceptor's third stage to be immediately ignited to divert to the intercept point predicted by the radar track.

During this third-stage divert, the KV seeker is uncapped to begin its search to acquire the RV and other objects in the threat complex. When the third stage burns out, the KV solid DACS is ignited to orient the seeker field of view to the predicted location of the target complex. Assuming a closing velocity of 5 to 6 km/s, three key parameters are as follows:

For the case shown, an arbitrary 10 s was allowed for these functions to occur, as indicated by the contour labeled 3BO +10 s and an arrow that points to where the target is at that time. It can be seen that for this particular set of conditions, the target had not penetrated the boundary, which means that intercept was possible given the stated assumptions.

A careful study of Figure 3.4 shows that:

Page 67

Many such cases have been run to establish the defended area and battle space for these assumptions, and several conclusions can be drawn. First, if the interceptor parameters used are representative of the SM-3, the current interceptor fly-out velocity is more than adequate for engaging descending TBMs as far as 50 km forward of the ship provided the radar can detect RVs at the detect range shown. However, the radar limits the battle space, allowing time for only a single shot or salvo against most threats. Second, if the smaller RV cross sections that can be expected in the future cause the detection range to be less than the arbitrary 300 km assumed here, substantial improvements in radar performance will be required just to provide self-protection let alone to project protection ashore. Third, since the intercept is exo-atmospheric and the interceptor cannot take advantage of atmospheric drag to help sort out the RV from the lighter objects, it must rely on more sophisticated measurements of the thermal, spatial, and temporal aspects of the optical signatures of objects in the threat complex. While radar improvements will also help provide more time for kill-vehicle on-board discrimination and homing functions, it will be necessary to increase seeker performance as well to take advantage of that additional engagement time.

Other TMD interceptors, such as THAAD and Patriot PAC- 3, are optimized for specific unique requirements and are generally less suitable for Navy applications. Both of these interceptors are much smaller than the SM-2 and SM-3 because they need to be transportable by air or ground vehicles. THAAD uses a liquid DACS that might support a backup option for SM-3. The PAC-3 active RF seeker may offer some additional robustness for certain kill-stage applications.

The committee emphasizes that at this time, the NTW effort is funded only as a demonstration, not an acquisition program. As a consequence, detailed planning and design are absent. The paucity of realistic engagement data offered for NTW suggests that an inadequate level of systems analysis has been done up to this point in the program. As a result, the committee relied largely on its own analysis to assess the capabilities of the NTW system.

Informal plans presented to the committee project a phase-1 system that barely meets initial requirements. There are strong reasons for proceeding, but only if both the Navy and DOD are committed to follow-on developments that will enable the NTW system capabilities to keep pace with the threat.

Page 68

Page 69

initial system, the committee believes that defense effectiveness can be enhanced in an evolutionary manner.

Page 70

would require a substantial effort. A number of CONOPS and weapon guidance options would need to be explored. Among the CONOPS and terminal guidance options that might be considered are the following:

Aircraft with AMRAAM missiles may have some capability against low-altitude cruise missiles, but sustainability considerations dictate that most of the defensive coverage for the area be provided by missiles launched from surface ships operating offshore. Except against cruise missiles that can be tracked by those ships, the Navy has no such capability at present, and the committee was unable to identify a program of record to develop such a capability.

Page 71

nonimaging IR seeker can acquire it. It is only effective against threats that employ active radar for terminal guidance. The Block I variant of RAM overcomes this limitation. Successfully completing its operational evaluation (OPEVAL) last year, RAM Block I has a much wider field-of-view IR seeker, which can acquire incoming threats based on shipboard radar handover alone. The RAM Block I is planned for installation on carriers and many amphibious ships. RAM's ability to attack at minimum range gives it capability against threats difficult for other missiles: some threats maneuver at a distance from the ship but reduce their maneuvering as they draw close to ensure that they hit the ship. The principal disadvantage of RAM's short range is its inability to handle high raid densities.

The close-in weapon system (CIWS) is on virtually all combatant ships. It is a closed-loop system in which a radar tracks both the threat and a gun's projectiles, judges the distance by which the projectiles are missing the incoming threat, and adjusts the gun's direction of fire. Its very short range makes it a last-ditch defense. CIWS was first introduced 20 years ago. Although many variants and upgrades of CIWS are now operational, there are some threats the system cannot handle. The Navy plans to replace CIWS with RAM.

The Navy is developing the evolved sea sparrow missile (ESSM) to handle emerging cruise missile threats, especially fast and highly maneuverable ones. The ESSM is a greatly improved upgrade of the sea sparrow; it provides a more powerful rocket motor, better aerodynamic control, and a new guidance system. ESSM is currently in development flight test, and at the time of this writing it is having some difficulty with radome failures. Navy presentations to the committee showed that either ESSM or SM-2 Block IVA is necessary to give surface ships adequate self-defense against the most serious air threats expected to emerge in 2005 or so. At present, the Navy plans to install one or the other missile only on Aegis ships, with ESSMs packed four missiles per vertical launch system (VLS) cell. The Navy once planned to install ESSMs on other ship classes, but to do this it needs an ESSM launcher, for which there is no program of record.

The SM-2 Block IVA provides Aegis ships with another weapon that could be used in self-defense, as well as in area defense or TBMD, as discussed else-where. Neither SM-2 Block IVA nor ESSM would be adequate against potential future air threats employing certain advanced countermeasures.

The MFR discussed above could be made to serve as an illuminator for semiactive missiles such as the standard missile or ESSM. The MFR will have a phased-array antenna, which should enable it to handle multiple missiles in terminal guidance, thereby improving defense against high raid densities. This is another reason to consider its use on Aegis ships.

The combination of the VSR, MFR, a weapon control architecture similar to that in Aegis, the SSDS, ESSM, and a robust electronic warfare (EW) capability should provide future combatants other than Aegis an adequate self-defense capability against most threats in the near term. Again, the threat can be expected

Page 72

to continue to increase, and future upgrades—to handle, for example, advanced countermeasures—will surely be required.

Page 73

attacking missiles arrive in shorter periods of time combine to make reaction time and firepower the principal challenges in shipboard weapon control.

The Navy's answer to the reaction time and firepower challenges is to rely on automation and to provide doctrine allowing the commander to depend on an automated response in high-threat conditions. To provide the capability, the Navy has also had to meet stringent launch control, launcher design, and illuminator requirements to fire and guide semiactive air defense missiles. The first implementation of this was in Aegis. For decades an Aegis ship has been able to have multiple missiles in the air against an incoming threat just a few seconds after establishing a firm track on it.

In recent years, the Navy has implemented an ad hoc capability for automated fast reaction in its other combatant classes. The SWY-1, -2, and -3 weapon control systems in these ships have a reaction time with a RAM that can rival Aegis's with a standard missile. The Navy now plans to replace this ad hoc weapon control capability with the SSDS—a modern, open, distributed architecture founded on a local area network (LAN). SSDS treats sensors and weapons as LAN access units, permitting easier replacement.

The Navy also plans to evolve Aegis toward an open architecture. When this has been done, the Navy will have the opportunity to standardize the command and decision (C&D) element of air defense systems on its various ship classes.

The Navy will soon have three levels of BMC3 systems applicable to area AAW, providing for three levels of operations:

The command and decision systems on Aegis cruisers and destroyers provide the first level; the CEC will enable BMC3 for a battle force; and the system being developed to support the area air defense commander will provide BMC3 for air defense within a theater. These systems are as applicable for TBMD as they are for area AAW and CMD.

The Navy and Marine Corps BMC3 for theater missile defense is discussed in more detail in the next section.

Page 74

system as (but greater maneuverability than) Block IV. Block IVA's imaging IR seeker will not be used against cruise missile or aircraft threats.

Page 75

~ enlarge ~
FIGURE 3.5 Missile defense BMC3 functions.

Page 76

control couple into platform and weapon management/control, as is necessary, for instance, to carry out fire control.

All the real-time functions noted above are performed according to plans developed in non-real-time planning, which may need to be revised in near-real time. For example, non-real-time planning determines initial platform locations, assigns sensor coverage areas, and provides rules of engagement.

The next section elaborates on operational considerations; the sections after that discuss how current and planned systems and programs relate to the achievement of these BMC3 functions.

Page 77

set up the necessary network configuration. Thus, the dated technology of Link 16 manifests itself by inhibiting operational flexibility.

Of necessity, all operations are likely to be jury-rigged. Operational concepts and the technical underpinnings should allow this ad hoc assembly of components and information exchanges to become a normal process rather than constantly repeated exceptions. Current Internet and Web concepts provide some elements of the solution (although this does not suggest that the Navy/Marine Corps should use the Internet in implementing the solutions). Commercial businesses often use Internet and Web technologies to assemble ad hoc participants and information sources to gain important new business capabilities. One outcome of the further development of this theme is a systems engineering process that accommodates the introduction of unplanned resources and capabilities ( Appendix C ).

These ideas on the flexible composition of forces are reflected in current naval thinking on network-centric operations.³ However, although the Navy in general appears to espouse network-centric ideas strongly, such concepts were almost totally lacking in the TMD briefings and reports presented to the committee. As the Department of the Navy and joint community move forward with developing TMD concepts and capabilities, network-centric ideas need to become much more prominent.

Page 78

~ enlarge ~
FIGURE 3.6 A theater-wide ballistic missile defense scenario.

the PAC-3 radar, and from the SBIRS sensors. The data will be used to decide whether the NTW system or PAC-3 will attempt to intercept a given incoming missile. The decision might depend on which has the better shot and where the debris may land. An additional requirement might be to keep the National Command Authority fully informed and in the decision loop as attacks unfold.

The second scenario ( Figure 3.7 ) involves cruise missile defense. Here it is assumed that the fleet has a dual defense role: it must protect itself and extend protection to Marines who have maneuvered far inland. In this example, the purely naval force has been augmented with an AWACS presence that serves to detect cruise missiles while they are still far inland. Some of the cruise missiles may contain explosive warheads (e.g., for attacking the Navy's ships) while others may contain chemical or biological payloads aimed at the Marine deployments and nearby cities. The enemy is postulated to have chosen to launch cruise missiles directly through the Navy's aircraft so that friendly planes, commercial aircraft, incoming cruise missiles, and interceptor missiles could all occupy the same airspace.

This second scenario poses extremely complex and difficult challenges for BMC3. First, the ships afloat and the AWACS must share a highly detailed

Page 79

~ enlarge ~
FIGURE 3.7 An overland cruise missile defense scenario.

picture of all the objects in the airspace (e.g., a SIAP) so that they can distinguish enemy missiles from friendly planes and from neutrals. To a large extent, this picture must be synthesized from radar inputs from both the afloat and aloft sensors since the cruise missiles may have relatively low observability. Second, this air picture must somehow be related to the ground picture so that the naval shooters know the current location of the Marine Corps. Third, the BMC3 system must help the commander decide in real time on the best locations for intercepting the cruise missiles so as to minimize collateral damage caused by their falling debris (chemical and biological). Fourth, friendly planes may need to be diverted in real time so that the Navy has a clear shot at the incoming cruise missiles. Finally, the National Command Authority may require an accurate and highly timely picture of the entire battle as it unfolds in order to oversee, and perhaps override, the local commander's decisions.

Note that neither of the scenarios is Navy/Marine Corps-only—one involves forces of the Army and the other forces of the Air Force. As such, they introduce inter-Service complexities greater than those in Navy/Marine Corps-only scenarios. In addition, both scenarios intertwine the National Command Authority fairly tightly into engagements that otherwise must move along tactical time

Page 80

lines. The committee believes that neither of these complexities is unlikely. Indeed, it believes that joint activities, very likely with a direct tie into the National Command Authority, are more likely to occur than a simpler Navy/ Marine Corps-only scenario. In such situations, a joint commander is likely to ask for as much help as is possible and is likely to be given whatever is feasible.

Page 81

For NTW and overland cruise missile defense, BMC3 begins to assume a critical importance. In general, the farther the Navy must stand off from a hostile coastline, the more it will be forced to rely on external sensors. Its reliance on BMC3 systems will grow accordingly.

There is every reason to believe that both ballistic- and cruise-missile threats will grow more stressing over time. Thus, even those scenarios that can at present be managed by platform-centric approaches—namely, area and ship self-defense—will in relatively short order become too stressing for that simple approach. They, too, will begin to require more complex BMC3 solutions. This is not a new phenomenon. The rise of the cruise missile threat led to the relatively complex and distributed CEC system for ship self-protection. In other words, as the threats become more sophisticated and more numerous, distributed BMC3 systems will grow more important. Such systems are, in essence, the glue that binds the widely distributed sensors and shooters that form the protective shield for naval forces.

In summary, BMC3 is already critical for the Navy's more stressing threat scenarios (NTW and overland cruise missile defense). As time passes, it will also become more and more critical for even relatively local types of defense since the evolution of the threats will require ever-more-complex defensive systems.

One further aspect of missile defense bears special mention. Overall, increasing threat levels lead to a radical physical separation of the sensing, shooting, and command components of the entire system—and, indeed, lead very quickly to systems in which these various functions are handled across Services. For example, the Army may provide the radar and the Navy may provide the missiles. Thus, the perhaps inevitable response to ever-growing missile threats leads to a system that is “joint” to a profound degree and as such may require a major change in Service cultures.

The Department of the Navy should therefore be placing a fairly heavy emphasis on its distributed BMC3 architecture and systems ( Figure 3.8 ). These systems are already important for the more stressing naval missions and will rapidly become critically important even for missions that can currently be handled by platform-centric BMC3 systems. These systems and the associated architecture are discussed next.

Page 82

~ enlarge ~
FIGURE 3.8 Increasing area coverage and/or threat level will require distributed BMC3.

The left-hand block in Figure 3.9 refers to time-critical (but not real-time) decision making and non-real-time planning. Various data feeds, including from intelligence sources and communication means, enter the global command and control system-maritime (GCCS-M). Some tactically derived information is input to the left-hand block, but an additional large source is the tactical digital information links (TADILs) shown in the right-hand block. The TADIL inputs are processed in the command and control processor (C2P) for use by the rest of the BMC3 system.

A more rational, modern design for the overall BMC3 system would recognize that there is significant commonality of purpose and use of the data inputs and processing in the right- and left-hand blocks. In particular, a more modern approach would move from the many special-purpose systems shown here to a configuration based on common standards and general-purpose communication and computing capabilities.

The center block in Figure 3.9 represents real-time and near-real-time decisions to allocate and launch defensive ship-based missiles. The components involved are the advanced combat direction system (ACDS), the SSDS, and the Aegis command and decision and display system (C&D/ADS). This module

Page 83

~ enlarge ~
FIGURE 3.9 BMC3 system architecture. DMS, defense message system; OTCIXS, officer in tactical command information exchange subsystem; TADIXS, tactical data information exchange system; CUDIXS, common user data information exchange system; NAVMACS, naval modular automated communications system; TACINTEL, tactical intelligence information exchange system; JTT, joint tactical terminal; CTT, commander's tactical terminal; TIBS, tactical information broadcast service; TDDS, tactical receive applications (TRAP) data dissemination system; ADS, advanced display system; CDLMS, common data link management system.

receives its data input from the CEC, which are netted Aegis radars, as well as from the TADILs and GCCS-M data sources. The Navy has been experiencing interoperability problems as it upgrades the components of this module. Those problems appear to be in the process of resolution. In the longer term, the Navy intends to replace this module with the so-called Aegis common command and decision system (CC&D), which will be based on a modular, open architecture that should help to minimize future interoperability problems.

The TADILs and CEC are essential for providing the sensor input necessary for the BMC3 process. Of the three TADILs shown in Figure 3.9, Link 16 is the primary one in Navy plans. Thus, CEC and Link 16 are discussed in more detail below. National information feeds (coming from the left-hand box) are also important, especially for cueing sensors. While there is no further detail to be presented here, it should be noted that the timeliness of delivering these data could stand improvement.

Page 84

The quality of the situational picture derived from the input data is of course critical and is a matter of much concern. A new effort, the SIAP System Engineering Office Program, is being established to address this concern. In addition, the area air defense commander (AADC) module has been established to provide a display capability to help time-critical (but not real-time) decision making and non-real-time planning. Both the SIAP program and the AADC module are discussed in more detail below.

Page 85

the basic tactical communications capability. A more modern approach based on commercial technology would appear to greatly increase bandwidth. As discussed in Appendix C , commercial wireless technology is advancing rapidly, and capacities of at least a few megabytes per second currently appear possible. The commercial technology appears to have the necessary quality of service for military applications, although jam resistance is not a significant factor in the commercial developments. Still, the commercial technology would offer a good base upon which to build a jam-resistant capability.

The Link 16 fixed-format message set—called the J-series messages—covers a wide range of information categories. Very important among these, of course, is the surveillance tracks detected by participants in a Link 16 net. To obtain the best data on a given target and avoid redundant tracks, Link 16 procedures call for the platform with the “best” track to have reporting responsibility and to be the only platform to report that track. In practice, this can lead to significant difficulties. Other message sets allow for mission assignment to attack a target, and still others provide precision position location information (PPLI) based on packet time-of-arrival measurements. This PPLI information allows for relative navigation and also serves as an identification means.

Since the Link 16 message set was developed in the context of air defense, it covers the sort of information needed for cruise missile defense. Ballistic missile defense, however, required new messages to be added—for example, messages referring to missile launch and predicted impact points, space tracks, and engagement status. These additional messages take a shoot-and-shout approach to ballistic missile defense, but they do not provide coordination among multiple platforms that could fire at a given ballistic missile.

Page 86

SOURCE: Information derived from McCloud, Kenneth L., “PMW 159 Advanced Tactical Data Link Systems (ATDLS) Program Office,” briefing to the committee on July 26, 2000, Space and Naval Warfare Systems Command (PMW 159A), Arlington, Va.

The advanced tactical data link systems (ATDLS) program office (SPAWAR PMW 159) develops improvements to Link 16 and related TADILs. These improvements are summarized in Table 3.2. In general, the committee supports these improvements, although it expresses some particular reservations in the more detailed discussion in Appendix B. These improvement programs have technical merit and are likely to provide substantial benefits to the Navy. However, they are best viewed as late-life upgrades to a system that is nearing the end of its technical life cycle.

Serious consideration needs to be given to a much more modern approach to tactical data links. Such an approach would use a well-defined layered structure, as in Internet technology, instead of mixing the distinct problems of radio frequency (RF) channel architecture and message format, as Link 16 has done. Such an approach would also build on the rapid advances now occurring in commercial wireless technology.

Page 87

biguous tracks of all airborne objects in the surveillance area.”⁸ This is the desired result of the integration of situation inputs in Figure 3.5, above. Such a result does not now pertain. Instead one finds missing tracks, multiple track designations for one object, track number swaps between objects, and object misidentification. These shortcomings have been manifest in real-world operations and detailed exercises such as the all -Service combat identification evaluation test (ASCIET) series.

The preceding section highlighted the problems of Link 16 with regard to network flexibility and capacity. These problems are partly the result of not obtaining a SIAP, but the set of causes is much larger and includes basic technical shortcomings, the inconsistent implementation of a technical capability across different platforms, and the absence of necessary procedures. The root causes of the problem are numerous and include the following:⁹

To confront the problem, the JROC directed in March 2000 that a SIAP system engineering office be formed.¹⁰ The SIAP system engineer is responsible for the systems engineering necessary to develop recommendations for systems and system components that collectively provide the ability to build and maintain a SIAP capability. By JROC direction, the Navy will provide the lead system engineer, the Air Force will provide the deputy lead engineer, and the Army will serve as acquisition executive.

The SIAP system engineer has emphasized the importance of establishing

8 Joint Theater and Air and Missile Defense/Combat Identification Division (J85). 2000. Theater Air and Missile Defense (TAMD) Capstone Requirements Document (CRD) (U), Draft, U.S. Joint Forces Command, Norfolk, Va., June 15 (Classified).

9 Wilson, CAPT Jeffery W., USN, “Single Integrated Air Picture (SIAP) System Engineering,” briefing to the committee on August 30, 2000.

10 While the committee was not briefed on the program, it should be noted that the Family of Interoperable Operational Pictures (FIOP) program being developed in the Office of the Undersecretary of Defense (Acquisition, Technology and Logistics) is addressing issues related to the SIAP effort.

Page 88

the necessary system engineering process and not just isolated improvements. Thus far, the office has identified candidate solutions to address the root causes noted above. Near-term emphasis will be placed on engineering and recommending SIAP-related improvements to fielded systems—in particular, identifying fixes to the joint data network (JDN). The JDN is the network formed from tactical data links, which in the future will be dominated by Link 16 for U.S. forces (but will also contain Link 22 for NATO forces).¹¹

The SIAP System Engineering Office was created to meet a critical need, and its activities thus far appear well directed. The committee believes that the Navy should support the activities of this office and monitor them to make sure they are meeting naval needs. The committee further believes that the SIAP system engineer should take an aggressive stance in promoting the development of modern alternatives that would eventually replace the current tactical data links.

Page 89

pants. A prioritization scheme has been developed to send the most relevant data to each participant within the limits of the available bandwidth.

Control of defensive missiles being fired using CEC data lies outside of CEC (in the C&D module in Figure 3.9 ). Thus, CEC does not form a complete BMC3 system, nor was it intended to; loosely speaking, it is a distributed sensor system.

Over the last half-dozen years or so the CEC components have been upgraded and modernized, taking advantage of advances in computer and electronics technology and making increased use of commercial components. The production of CEC components began in 1998 at a low rate. Currently, CEC version 2.1 is undergoing large-scale, at-sea testing (the so-called Underway series).¹³ Operational evaluation is planned for the spring of 2001. Version 2.1 will provide an air-defense capability; ballistic missile defense capability is planned for version 2.2.

Page 90

track data over an improved tactical data link capability, as could possibly be realized through the SIAP program, would be adequate.

CEC is also being proposed for uses where there would be little overlap in coverage between sensors. For example, an advanced concept technology demonstration is exploring coupling Aegis and Patriot via CEC for low-altitude cruise missile defense. The main benefit of CEC appears to be that it provides a composite track picture from overlapping sensor coverage, in which instance it is valuable for exchanging measurement-level data. When the coverage regions do not overlap significantly, it could suffice just to send track data, which could be done via a (possibly enhanced) tactical data link.¹⁵

The committee believes CEC can provide a valuable capability for ship self-defense and overland cruise missile defense if adequate overland sensors are available in the latter case. The committee does not have adequate information to take a position on the issues of extended use noted in the last two paragraphs. However, it believes that the Department of the Navy and the joint community should conduct adequate analyses to resolve these issues if they have not already done so. No such analyses were apparent in the briefings received by the committee.

Rather, it appeared that since CEC was an existing capability, at least in prototype form, it was being extended to new uses without an adequate analysis of the alternatives and trade-offs involved. The advantages of using an enhanced tactical data link capability could be reduced cost and greater operational flexibility in passing the data, since tactical data link terminals will be more widely deployed. Furthermore, just as one should guard against locking into legacy Link 16 technology, one should also be cautious about locking into CEC technology. While CEC is highly capable, it must be kept in mind that it is based on an architecture first designed in the 1980s.

Page 91

The AADC module display shows air and ballistic missile defense assets, hostile forces, and neutral entities—all depicted as the real objects in a three-dimensional representation instead of in terms of some abstract symbology. This information is updated through information feeds such as Link 16.

In joint operations, the joint force air component commander (JFACC) air-space control authority (ACA) prepares the airspace control order (ACO) that determines the partitioning of the airspace to deconflict the various offensive and defensive assets that will be operating in it. The AADC module provides a three-dimensional rendering of this partitioning. In addition, it displays such operational parameters as the coverage areas of surveillance systems and the range of weapon systems. It also supports collaborative planning by providing a visual teleconferencing capability.

The AADC supports both planning and execution. Its displays and tools allow the initial positioning of air defense forces to be determined much more rapidly than with the conventional manual procedures. However, the material presented to the committee on the AADC module did not appear to indicate that the operational concept for the interaction between the AADC and the JFACC had been fully worked out—for example, the concept for the coordination and airspace deconfliction of offensive and defensive operations, which is necessary to take full advantage of the AADC module's capability. Similarly, further development of the operational concepts for joint ballistic missile defense also appears to be required.

In execution, the AADC module's display and tools allow for the near-real-time tasking and redirection of defensive assets. This capability should aid tactical command and control of defensive operations significantly. The committee did not, however, receive adequate information to be able to assess the sufficiency of the AADC module's battle management tools. That is, while there is significant capability in the module now, further automated battle management aids could be desirable to cope with complex, multitarget situations.

There is an important cautionary note pertaining to accuracy: The AADC module's display is very realistic. Such displays can lead observers to believe that is how the real situation is, when in fact there can be errors in location, identification, and completeness in the data input to the display. Operators should guard against taking the displays more literally than is warranted. Means should be sought for depicting the uncertainties in the AADC displays. Furthermore, safeguards against the engagement of neutral targets—such as the inadvertent shooting down of an Iranian Airbus in the Gulf many years ago—must be incorporated in the system. For example, as currently envisaged, the AADC makes no use of the Official Airline Guide, and it has no links to civilian air traffic control.

AADC prototype modules have been installed on the command ship USS Mount Whitney and the cruiser USS Shiloh. The prototype module on the Shiloh was used in the rim of the Pacific (RIMPAC) exercises in the summer of 2000. Its use was apparently well received. Further testing of the AADC module is

Page 92

planned, for example in the Abraham Lincoln battle group, and initial operational capability (IOC) is planned for FY06.

In summary, the AADC module should provide a valuable capability supporting those management/control functions shown on the right-hand side of Figure 3.5, above, as well as the non-real-time planning function. However, as noted, further development of the operational concepts necessary to execute these functions could be warranted, and serious consideration needs to be given to the representation of uncertainty in the battlespace display.

Page 93