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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY WARFARE SUMMARIES Antisubmarine Warfare Background Dr. Arthur Bisson noted during the symposium that the three most important problems related to ASW operations in shallow coastal waters today are “detection, detection, and detection.” The ocean environment adds “stealth” capabilities to submarine vehicles. Consistent detection is difficult in the coastal ocean, because this environment can be highly variable in water temperature, salinity, turbidity, concentrations of organisms, and bottom characteristics, in both topography and composition. The coastal ocean also features high levels of natural ambient noise. Navy technology is not as advanced for shallow-water detection as for open ocean ASW because shallow-water acoustical detection is inherently more difficult and, until recently, there was no significant shallow-water submarine threat. Since the 1960s, the Navy has focused its acoustic ASW approach on the passive detection of Soviet nuclear submarines operating in deep water. Active sonars such as the SQS-26 and 53 have been developed but were generally designed for convergence zone and single bottom bounce environments. In the next decade, political and economic instability may occur in many regions of the world. The coupling of this instability with the proliferation of small, relatively inexpensive diesel submarines among developing countries will shift the submarine threat. In addition, new submarine propulsion systems and more effective weapons are likely to be developed. All these factors suggest that military and scientific attention must be increased now, to improve the Navy's ability to conduct shallow-water ASW. A balanced Navy approach would require more shallow-water ASW to complement ongoing research in deep-water ASW. Despite these difficulties, there remains a significant spectrum of operational and technological opportunities with the potential to improve our shallow-water ASW capability. For example, submarines operating in shallow water are relatively near the surface, allowing more effective application of nonacoustic techniques, (e.g., laser technology and stimulation of bioluminescence) than in deep water. Technology has always been the Navy's “force multiplier,” allowing our fleet to operate more effectively than other nations navies of similar size. Ocean scientists have a strong role in determining when shallow-water ASW techniques are technology or environment limited. From a technology standpoint, for example, what coastal environments preclude cost-effective development of acoustic detection? Can the Navy improve its detection success by integrating acoustic and nonacoustic sensors? Development of the necessary techniques will require that
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY existing R&D efforts be maintained and focused on coastal applications. A healthy R&D foundation must be sustained so that attempts to “reconstitute” that capability will be successful. Discussion The discussion session began with a presentation by a representative from the Naval Underwater System Center's Surface ASW Directorate who discussed the most pressing issues in shallow-water ASW. The three primary issues are: Variable performance owing to environment and season. - The performance of ASW techniques depends on the season and the unique environment of the coastal site. Seasonal water column conditions (particularly summer versus winter) are inherently more variable in shallow water than in deep water. Further, bottom conditions vary in different operating areas as a function of grazing angle and frequency. Because system detection performance is highly sensitive to these variabilities, system design must account for them. Boundary interactions. The effects of the seafloor and the sea surface on acoustic systems in shallow water are highly complex, making range predictions difficult. Multi-path degradation affects overall figure of merit and active classification. As a result, false target identifications are frequent. Practical limitations. Another key issue is the range dependence of shallow water propagation and reverberation. For example, shallow water limits the depth of towed sound detection arrays, thus increasing the possibility of the system's detecting its own noise. In addition, closer ship spacing increases the potential for mutual interference effects. A recent workshop on the role of ASW in regional conflicts identified two general S&T areas that could support shallow-water ASW: Developing affordable detection systems that work against quiet submarines moving through turbid and complex environments and Understanding the technical limits of acoustic methods, for example, how many data are needed to predict both sound and light-based performance and whether the necessary data can be collected quickly enough?
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY S&T Requirements The discussion group highlighted the following issues and topics that depend on knowledge of the environment: Weapons. Navy representatives stated that the United States does not have an effective shallow-water ASW weapon. Specifically, present weapons cannot compensate for larger errors in target position. Acoustic weapons that are effective against slow targets with a low doppler signature are needed. Weapons used in shallow water must also have a lower unit cost because of the higher probability of firing weapons on false targets. Optimized Sonar. All types of sonar (e.g., hull mounted, sonobuoy, low-frequency active, towed arrays, side scan) operate less effectively in shallow water than in deep water. In the near term, our understanding of the technological and environmental limitations must be improved to adapt sonars that were designed for deep-water operations and are to be used in shallow-water. For the longer term, new sensors specifically designed for shallow-water operations need to be developed. Nonacoustic sensors. Nonacoustic ASW methods become more important in shallow water to complement the performance of acoustic sensors with the larger positional uncertainties associated with shallow water detections. Opportunities for nonacoustic detection exist with ship and airborne sensors of magnetic, optical, bioluminescent, chemical, and hydrodynamic disturbances. Bistatics Distinct source and receiver teams, off-board sensors, and low frequency operations will be essential. Operational experience against diesel submarines. Because small diesel submarines are one of the principal threats to U.S. forces, collection of performance data under a variety of environmental conditions is a high priority. These data could be collected during allied country exercises (e.g. by UNITAS and NATO) when participating countries operate diesel submarines. Another option is for the United States to purchase an appropriately configured new generation, conventionally powered submarine and to conduct shallow-water exercises against it under a variety of environmental conditions in order to determine the ability to detect and deploy counter measures as a function of environmental conditions. Connectivity. There is a need to improve coordination among ASW facilities by pooling the lessons learned and comparing the operational results noted in coastal regions.
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY Exploiting the environment. Is it possible to understand the shallow water environment well enough to exploit it? Under the new threat scenario, it is important to understand a few environmental regimes and geographic regions well rather than to attempt to characterize the entire world ocean. The likelihood of conflict in a given region should direct data collection and evaluation activities. A potential new approach to detection in high noise environments similar to the mine warfare Q route surveys was suggested. In this approach, environmental plots of sonar performance and geoacoustic parameters would be developed and stored for areas of potential conflict. The background maps would be used later in naval operations to detect submarines, which would appear as departures from the background profiles of data previously collected. Rapidly deployable surveillance systems. Systems combining acoustic and nonacoustic sensors with oceanographic and meteorological monitoring sensors would be a considerable improvement. Acquiring environmental data in enemy territory under war conditions will be essential; speed of deployment is often crucial. Shallow water fleet exercises. Performance-testing exercises, (e.g., the Ships ASW Readiness, Effectiveness, and Measurements (SHAREM) series) can be valuable in assessing performance in potential conflict areas. The SHAREM exercises have collected comprehensive data on operating and environmental parameters for more than 90 exercises in the series. Five recent exercises have been conducted in shallow-water areas using 209 class diesel submarines as targets. In these exercises, shallow-water results generally indicate limited acoustic performance, but radar periscope detection by certain sensors showed some promise. Gray ship data collection of opportunity. Group members urged use of a wider range of Navy resources (e.g., non-oceanographic ships of the fleet) to collect identified environmental and operational data, especially in the most likely regions of future warfare. Communicating to fleet personnel the importance of collecting these data would improve the precision and specificity of data from this source. Remotely operated vehicles. Remotely Operated Vehicles (ROV) should be developed or adapted for use in investigating false targets, bottomed submarines and mines in shallow-water operations. Tactics. Changes in tactics should be considered to make better use of existing ASW systems. Improved understanding about why certain systems do or do not work in shallow water is required. Better understanding of system performance is needed to guide sonar placement. The SHAREM program and its vast data base of
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY many key variables should be analyzed more extensively in addition to designing new exercises to collect required performance data. Systems approach. A systems approach to ASW should be used, whereby the shallow-water mode chosen determines what environmental factors should be monitored. The Office of the Oceanographer of the Navy previously indicated that shallow-water ASW is a “systems hardware problem.” Until suitable coastal sonar systems are provided to the fleet, the benefits of operational oceanographic support are limited to range predictions and mode assessments. Amphibious Warfare Background Amphibious warfare specialists noted that the strategy behind amphibious operations has changed considerably since World War II. A new “Over the Horizon” (OTH) concept has been formulated, in part as a response to development of antiship missiles that now pose a threat to amphibious task forces. These new missiles have increased ranges that require amphibious assaults to originate farther and farther offshore. The OTH concept's goal is to turn a disadvantage into the tactical advantage of surprise. Another difference between World War II tactics and the modern amphibious concept of “maneuver warfare” is that this new approach is based not on geographic goals but on the “mind of the enemy commander.” The objective of the attacking force is to produce chaos among the defending forces (while coping with chaos) by continuously adjusting the focus of the attack. This objective is achieved by decentralizing decision making, communicating the big picture, so that subordinate commanders can select appropriate alternatives to achieve the warfare goal, surmounting obstacles as they are encountered. An example of this fast-paced warfare is a hypothetical task force operating off the coast in the vicinity of Norfolk, Virginia. The task force could attack anywhere along the coast from New England to the Carolinas within 24 hours. A major consequence of this doctrine of constant adjustment is that weather and oceanographic conditions must be monitored and forecast continuously, exploiting opportunities for offensive or defensive activities as environmental conditions allow.
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY Discussion The major problems and issues confronting an amphibious group commander include: Mines. Detecting and avoiding shallow-water mines is critical to an amphibious assault. The uncertainty about the presence of mines in the shallow waters of coastal Kuwait may have been the major factor in the U.S. decision not to launch an amphibious attack. Some promising research has shown that remote multispectral sensing can be used to detect mines. For example, Synthetic Aperture Radar (SAR) shows promise as a means of detecting the surface expression of characteristic radial wave patterns caused when wave trains interact with subsurface obstructions. Other potential techniques focus on airborne laser (i.e., light detection and ranging (LIDAR)) instruments for mine detection and use bioluminescence to detect wake trails around underwater obstacles. Submarines. The proliferation of quiet diesel submarines in developing countries is a major new threat to amphibious operations. The group did not discuss this subject in detail, deferring to the ASW warfare group. Bathymetry. Several key operational (e.g., feasibility of using landing craft to offload tanks) and environmental factors (e.g., wave and surf conditions) are influenced by nearshore bathymetry. Consequently, measuring nearshore bathymetry accurately is a priority research area. The three potential technologies discussed specifically were airborne LIDAR systems, wave pattern analysis from multispectral imaging, and the use of ROVs for bathymetry measurements. Beach trafficability. Trafficability, the ease of moving equipment over a beach, can be inferred from measurements of the Rated Cone Index (RCI). The RCI is a function of soil moisture, dominant mineral type, grain size, and other factors. Efforts have been made to calculate the RCI remotely from multispectral imaging. The Army has also attempted to measure the RCI directly by in situ techniques. The Army has developed and tested a device called a drop penetrometer. As its name implies, this device is dropped from an aircraft; the RCI is calculated as a function of the depth of penetration, and telemetered to a remote location. In principle, it is possible to determine the RCI (and infer trafficability) by integrating multispectral imaging and in situ penetronometer measurements. Marine weather and ocean state forecasts. As noted earlier, modern amphibious warfare requires continuous environmental forecasts to maintain maximum operational flexibility and to exploit opportunities in air-sea conditions favorable to
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY allied military actions. Environmental specialists attempt to identify the key parameters (discussed below) and forecast the variability of these parameters. The goal is to reduce the likelihood of an environmental surprise and provide options for amphibious operations. Access to real-time observations (either from expendable in situ devices or through remote sensing techniques) is a basic deficiency. Forecasts, possibly hourly, may be required to maintain pace with a “fast break” philosophy of warfare. Key forecast parameters include: Tides. Few tidal observations are presently available from ports and coastlines in the developing world's potential conflict areas. Even if they did exist, it is unlikely that tidal observations would continue to be available once hostilities became imminent. The important capability regarding tides is predicting the tidal ranges and time of tidal exchange. Site-specific numerical models are needed, including meteorological and hydrological forcing functions in addition to the astronomical and ocean components of the tidal forcing function. Currents. Detailed and accurate current predictions are also needed. As with tide predictions, accurate current predictions require development of numerical models of coastal regions of high interest. Accurate bathymetric information as well as access to a variety of environmental parameters to initialize models and verify model performance, is also required. Surf conditions. As noted earlier, the accuracy of surf forecasts is strongly influenced by the accuracy of the bathymetric characterization. Forecasts of wave spectra, the number of waves of different heights and periods, are also required. Wave spectra forecasts are presently available from the Fleet Numerical Oceanographic Center for the entire world, and the techniques to account for bathymetric effects on waves as they move toward shore are well-understood. Thus, the primary factor limiting the accuracy of surf forecasts is accuracy of bathymetric data. Sea surface temperature (SST). SST is important primarily because it is used in calculating the refractive index of the upper ocean for electro-optic propagation considerations. SST variability, such as that caused by surface fronts, can change refractive indices and present problems for an OTH amphibious force. Low level aviation forecasts. Forecasts of low-level clouds, visibility, and winds are required for helicopter assault operations. Again, real-time observations are critical to accurate forecasts.
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY Intelligence gathering. Intelligence needs to be gathered quickly, it must be accurate, and means must exist for its distribution. It was noted that the Navy will not launch an amphibious assault until Special Operations personnel have provided on-site observations. These observations include beach trafficability, beach gradients, bottom composition, the location of obstacles, and a number of environmental observations, such as surf conditions, tides and currents. Although Special Operations personnel can provide highly accurate observations in small areas, the total coverage is limited, accurate positioning information is difficult to obtain, and significant obstacles can be missed if these obstructions occur between “the swimmers.” The group agreed that a combination of remote and in situ techniques and systems need to be developed to provide these observations, reducing the heavy reliance on Special Operations personnel. Poor roads in developing countries. Future conflicts will take us to locations where the roads are poor and maps lacking. Heavy rain and other adverse weather conditions can degrade travel conditions on poor roads. Accurate coastal weather forecasts can help the forces prepare for difficult travel conditions. Mine Warfare Background Mine warfare faces several challenges in the future. Foremost are the shortage of experienced officers and the introduction of several new mine-hunting platforms that require updated tactical review. Navy mine hunters still use heavy, awkward World War II vintage mechanical rigging that could benefit from modern material S&T. Further, Operation Desert Storm showed that we must deal with a wide variety of shallow-water mines. The Navy has little shallow-water mine countermeasure experience and generally it underutilizes available environmental data. An improved drift model and better data collection are needed to help both the on-scene commander and mine warfare pilots. A brute-force, large-area mine neutralization capability is needed. Discussion Several potential mine detection methods and countermeasures were discussed. Some are unworthy of further consideration at this time: artificial tsunamis, gravity measurements, and real-time overhead TV imaging. Other technologies that could be used for these purposes but are not yet employed included:
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY Radar wave tracking (tracking internal wave anomalies). The moored mine may leave an internal wake that could be detected by radar. The capabilities of several existing laser and SAR detection techniques were discussed. SAR could detect a disturbance in the general current flow, but only if the object was no deeper than its diameter. Certain laser systems could detect mines if the overlying water was clear enough for the system to image enough of the object to identify with pattern recognition techniques. This technique would be a problem in turbid water or surf. In the short term, the Navy should take advantage of existing tests of these systems and moor some mines in the test areas. Several other suggestions for shallow subsurface detection include a bioluminescent wake study. This area could profit from further research. Real-time acoustic measurement. Minesweepers presently cannot measure either ambient noise or their own noise, reducing the effectiveness of minesweeping operations using acoustic techniques. Solving this problem would not require new technology; minesweepers could be refitted with the addition of components for measurement directly from existing sonar systems. Real-time magnetic measurement. The magnetic signature of the minesweeper, the sweeping device, and the ambient magnetic field (from sunspots and local magnetic anomalies) must be known to calibrate minesweeping equipment. British minesweepers successfully used magnetic detection of mines in the Persian Gulf. Daily data on sunspot activity supplied magnetic data needed by mine warfare personnel. Local magnetic data could be obtained by trailing a sensor from a balloon or an ROV that measured conductivity. Again, the technology requires only a refitting to make it useful to the mine warfare community. Real-time bottom mosaic. There is a need to be able to do real-time, high-resolution sonar imaging of the bottom for mine and obstacle detection. Existing commercial sonar image-processing systems designed for small boats can produce bottom images in near real time, provide georeferencing of all data points, and include the capability of pattern recognition. Thus the technology for real-time bottom mosaics exists, the mine warfare community needs only to identify its specific requirements. Distributed explosive. In this technique, an explosive compound is spread across the mined area. When detonated, the explosives create enough concussion to detonate any mines in that area. Dense gel and fuel-air explosives have been tested. Gel explosives were ineffective, but the fuel-air explosives were effective to an 8 foot depth. In deeper water, the attenuation of the blast did not allow the
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY concussion necessary for mine detonation. Further study is merited for distributed explosives. Inexpensive propelled neutralization charge. A self-propelled, guided, expendable detonation device would be sent to each mine or obstacle from a small boat or plane. Such a neutralization method would require a low per-item cost, yet include some sort of programmable global positioning system-based guidance system. A 20-pound shaped charge detonating within 9 feet of the mine should disable it. There were discussions about the remote guidance systems needed to control such devices and launch platform characteristics. A bottom crawling vehicle that carried satchel charges and moved from mine to mine by remote control was also proposed. Further study on this topic would be beneficial, with a determination of the feasibility of one-by-one detection methods. A related subject that deserves further attention is riverine warfare. Strike Warfare Background and Discussion A representative from the Naval Strike Warfare Center at NAS Fallon, Nevada, discussed strike planning methods and identified environmental factors of primary importance, almost exclusively focused on atmospheric processes: Winds at the target. Accurate forecasts of surface winds at the target site are required for target selection and attack sequencing. Strike pilots select individual targets from a group of targets so that the smoke from the first one attacked does not obscure the remaining targets. Winds enroute. Enroute winds are important in the accurate targeting of Tomahawk and Harpoon cruise missiles. They are also a consideration in deciding where to carry out in-flight refueling operations. Clouds and visibility. The single most important environmental consideration in deciding whether to use “smart weapons” is the degree of visibility at the target. Laser-guided weapons depend on a clear path between the weapon and the target. In addition, the Tomahawk cruise missile uses a visual cue in the final target “acquisition” phase, and in-flight refueling operations require good visibility in the refueling area. Refractive index. Accurate determination of the atmospheric refractive index for coastal missions is an important area of potential research. The refractive index is poorly modeled over land. The transition from the nearly homogeneous air over
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY deep water to the highly variable coastal regime introduces errors in refractive index calculations. Temperature and humidity. Forecasts of temperature and humidity are important considerations in Tomahawk cruise missile attacks. If the missile must climb over mountain ranges to reach its intended target, accurate temperature and humidity data must be available to the strike planner. Sea state (wave height). Sea state forecasts are important for Harpoon cruise missiles because these weapons use active systems to acquire their targets. At certain sea states, the Harpoon may not be able to distinguish its intended target from the background ocean surface. Sea state and surface layer winds are also important to strike planes as they return to the carrier and attempt to land. Naval Special Warfare Background The original mission of naval special warfare (NSW) operations was to identify safe landing zones for an amphibious assault by performing detailed hydrographic surveys. These surveys described bottom characteristics and depth, and the location of obstacles, including mines and mine-like objects. Since formation of Naval special warfare teams during World War II, the NSW mission has expanded to include direct attack, search and rescue, and reconnaissance in all environments from sea to mountainous cold-weather regions. A potential new role for NSW personnel is the neutralization of mines, once found. Currently, they are not trained for this mission. Sea-air-land personnel (SEALs) are not EOD personnel, and NSW's primary environmental concern is to minimize its degrading impacts on the performance of personnel. Detection and avoidance of mines and mine fields are more in line with the training of NSW personnel. Discussion Environmental data support for NSW is concentrated in two broad areas: mission planning and nearshore operations. Mission planning. Navy special warfare teams and their Marine Corps NSW counterparts are often required to operate with little or no knowledge of enemy activities. Thus any environmental information that describes conditions is advantageous. A general description of the coastal environment may provide enough advance warning to avert compromising a mission. Environmental information important for mission success includes meteorological and
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY oceanographic climatology and coarse-scale marine geology and geophysics products. Frequent updates are desirable to reduce surprises and improve the likelihood of mission success. The two means for accessing environmental information for mission planning are direct support from the oceanography community through field activity of the Naval Oceanography Command (COMNAVOCEANCOM) and incorporation of environmental data bases into the Special Operations Planning and Rehearsal System. Naval Special Warfare (NSW) is the only warfare task area which does not enjoy the dedicated assignment of a military oceanographer (naval officer designation 1800). Oceanographers are seldom brought into the planning phase or consulted after crucial decisions have been made. Oceanographic input could be improved by establishing oceanographer billets in the two SEAL groups and deploying mobile environmental response teams to collect real time data. The Nearshore environment. The nearshore environment is a growing importance in NSW mission because the coastal zone of operations has a lengthened delivery (transit) distance and more accurately defined approach lanes. The purpose of a NSW hydrographic survey is to refine coarse data with detailed data gathered by NSW personnel on site. Environmental parameters of interest include: Good/best area for amphibious assault (reducing the number of potential landing sites is crucial), Swell height, Nearshore breaker height predicted from swell and bathymetry, Nearshore currents (especially as they affect Swimmer Delivery Vehicles (SDVs), Tides and astronomical data affecting available light, Water clarity and temperature throughout the entire water column, Bioluminescence, Extended outlook weather forecasts to assign boundaries to likely environmental conditions, followed by regular updates regarding fog and clouds and other variables.
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SYMPOSIUM ON NAVAL WARFARE AND COASTAL OCEANOGRAPHY SEALs require information on small-scale environmental effects because their missions are primarily restricted to their immediate surroundings as extended by a variety of delivery vehicles. Other S&T priorities include development of nonmagnetic equipment for mine detection, robotics to keep SEALs out of mine fields, and better long-distance communication to the task force commander in the new OTH scenario. Small, lightweight, rugged personal equipment is also needed (e.g., waterproof radios, body armor). The first step in improving environmental support is to improve communication between the NSW and oceanographic communities. SEALs receive no formal environmental training; the oceanography community could assist. As mentioned above, oceanography officers could be assigned to the special warfare command, although the Oceanographer's available personnel are limited in number. Mobile meteorology teams for special operations as well as application programs on the Tactical Environmental Support System (TESS) tailored to SEAL and Marine Corps problems could also improve communications and support.
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