The Role of Multifunction Radio-Frequency Sensors on Maneuver Vehicles

the EO sights. AESA radar constantly scans the full 360-degree horizon and au-The Role of Multifunction Radio-Frequency Sensors on Maneuver Vehicles by Dr. John S. Reed tomatically establishes a persistent view of “tracks” of all ground moving objects within the sector. By projecting these tracks in real-time onto a single geo-referenced station map display, leaders at the section and platoon levels have persistent situational awareness of all moving targets in their areas of operations. Using this CCTR radar picture, noncommissioned-officer leaders can then slew EO sights onto the most threatening potential targets and, if appropriate, slew organic weapons for engagement.

Modeling and simulation exercises, based on the seizure of al-Najaf in Iraq in 2003, demonstrate vast improvements in military utility criteria when AESA radars are used to complement EO sensors. Studies show that CCTRs integrated with EO sensors reduce time to first detection by 40 percent over performance by an EO sensor alone. This allows increased detection, identification and engagement ranges. Large numbers of targets previously overlooked by EO sensors alone, because of their restricted fields of view and manual scanning, are revealed to recon and maneuver small-unit leaders – an average of 46 percent more targets than detected by EO sensors alone. Overall, combining AESA radars with EO sensors reduced the time to complete the al-Najaf operation by about 35 percent in this exercise. Air situational awareness/force protection. Using the same principles, AESA radars provide air situational awareness and related force protection directly to small-unit leaders throughout the BCT and BfSB AOs. Any moving airborne objects

– fixed- and rotary-wing aircraft, unmanned aircraft systems, cruise missiles, etc. – are automatically detected, tracked and reported, initially on a visual display for the individual platform commander but also through the forward-area air-defense command-and-control network for incorporation into the common air picture. Because of the ability to mount these small sensors on virtually any combat or tactical platform in the BCT, small-unit leaders can now have an organic, on-the-move capability providing autonomous air situational awareness and force protection. With the exponentially growing threat of small, slow-moving and low-altitude enemy recon and attack unmanned aerial vehicles, the importance of this organic capability to the small recon or maneuver element is magnified, especially when standoff radar assets cannot see the small UAVs due to terrain masking or standoff range. As the U.S. Army develops enhanced FAAD capabilities – gun or missile – AESA radar capabilities can provide small-unit fire-control capability as well.

Counter rocket/artillery/mortar force protection. Recon, cavalry and maneuver elements can mitigate most threats of indirect fire simply by moving. However, when at-the-halt – whether part of mis-Figure 1. CCTRs provide autonomous, organic situational awareness and force protection to small-unit leaders against moving air and ground threats in complex terrain where less agile sensors cannot go. sion execution or for rest, refueling or resupply – even these highly mobile elements become vulnerable to rocket, artillery and mortar fire.

A special case of air situational awareness and force protection, CCTRs can provide sense-and-warn and counter-fire capabilities to autonomously operating small units and widely dispersed combat outposts not covered by longer-range C-RAM systems. Exercises at Fort Benning, GA; Fort Dix, NJ; and Yuma Proving Ground, AZ, since November 2009 have demonstrated the ability of current ground AESA CCTRs to provide useable, real-time point-of-origin and point-of-impact data; warn personnel to take protective measures; and allow leaders to initiate counter-fire. As is the case in the air situational awareness/force protection mode, CCTRs give the small-unit leader an organic, autonomous C-RAM capability unhampered by complex terrain or long distance from the nearest fixed-site C-RAM sensors.

Other key functions. While the preceding functional modes of AESA radars are well advanced along the path for fielding, more potential capabilities are at various stages of government and/or industry development. These capabilities include high-bandwidth communications, combat identification, Active Protection System fire control and indirect-fires support. For high-bandwidth communications, directional and rapidly steerable beams of the AESA radar can carry high-bandwidth communications to and from small recon, cavalry and maneuver units at the tactical edge of the BCT and BfSB AOs. Specific potential benefits include the ability to communicate during operations in improvised-explosive-device-infested regions despite active friendly (or enemy) jamming and the ability to pass streaming video from highly capable EO sensors into squadron-and-above tactical-operations centers.

For combat identification, a more specialized application of the communications function, millimeter-wave AESA radars can provide the interrogator function for the Battlefield Target Identification Device.

For APS fire-control applications, efforts to reduce the weight of combat platforms to make them more deployable and flexible on the battlefield have led to research and development of APSs that defeat incoming rocket-propelled grenade, anti-tank guided missiles and tank-fired rounds. Already demonstrated to defeat RPGs while on the move, existing APS packages can use an onboard CCTR with the detection, track and fire-control sensor and to direct the APS countermeasure to destroy the incoming threats. For indirect-fires support, the rapid local-horizon scanning capability of AESA radar permits it to locate obstructions in projectile lines of flight – mountains, buildings, etc. This essentially creates a map of the clear fire regions that is dynamically updated as the gun position or surrounding environment changes. Also, because of the ability to precisely measure the muzzle velocity of outgoing rounds, CCTRs can substantially improve the accuracy of artillery fire. Overcoming maneuver-vehicle radar concerns Incorporating RF technologies – radio and radar – into fast-moving, agile maneuver forces has been hampered by two traditional characteristics of these RF systems: the ability of enemy forces to detect, locate, intercept and attack systems that emit an electronic signature in the battlespace and the large size, weight, power and cost demands of traditional radars. Recent advances in technology for AESA-based CCTR systems substantially mitigate both these barriers. Traditional RF emitters send out continuous, omni-directional and/or predictable signals in frequency bands for which spectrum analyzers are widely available. Here, the potential for a hostile receiver to be at the proper frequency and within range for a sufficient period to detect, locate and intercept the emitted energy is high. AESA-based CCTRs, on the other hand, have a dramatically lower probability of detection/intercept relative to the traditional battlefield emitter. CCTR beams are very focused (typically 3 degrees or less) and randomly hop continuously and quickly throughout the search volume and across a wide and randomly selected part of the frequency spectrum. These characteristics make the threat receiver implementation impractical. Even if the enemy determines there are energy emissions somewhere in the vicinity, AESA beams move in space and frequency so quickly that they cannot be located, let alone intercepted for exploitation. The second key barrier to U.S. Army warfighter exploitation of traditional radar capabilities on maneuver platforms has been the equipment’s SWaP-C demands. Technological advances in AESA components core to CCTRs have significantly mitigated these SWaP-C considerations. With millimeter-wave antennas less than half a cubic foot in volume, the practical result has been the development of radars small and light enough, and with such a reduced power demand, as to permit mounting them on virtually every combat and tactical platform in the Army inventory.

Operationally, this means that for the first time NCO leaders in scout/recon sections, armor/infantry platoons and target-acquisition teams could have an organic situational awareness and force protection RF capability. Moreover, the influx of newer platforms – especially the mine-resistant, ambush-protected all-terrain vehicle and Joint Light Tactical Vehicle (in place of the currently overtaxed humvee) should fully eliminate any SWaP-C limitations. Perhaps equally important, advances in RF packaging that advantage the commercial-electronics manufacturing industry (for example, cellphones) now enable affordable AESA implementations for many mission equipment packages across a BCT or BfSB.

While “bigger is always better” is the first reaction from the user of any standoff sensor desiring to provide situational awareness and force protection to a vastly extended maneuver element, operation in complex terrain and while on the move frequently prevents the “bigger” material solution from being entirely effective. Per Figure 2, by simply task-organizing a limited number of “smaller,” more affordable AESA CCTR assets through the maneuver-element AO, the same degree of situational awareness and force protection will result in the environments typical of theater operations today. There is a certain degree of redundancy in case some of the local sensor assets are inoperable. If network assets are available (or enabled by using the radar as a communications aperture), the outputs of the distributed vehicle radars can merge into a single common operating picture.

Summary

With recent technical advances, multifunction AESA radars can now deliver critical situational awareness and force protection capabilities to the smallest, most exposed recon/cavalry sections, maneuver platoons and target-acquisition teams at the tactical edge of the BCT and BfSB battlespace. This multifunction RF capability is provided on themove and while operating in complex terrain that may prevent standoff radar assets from detecting local threats. Dramatic reductions in SWaP-C requirements and vastly mitigated vulnerability to hostile electronic direction-finding and intercept have enabled full realization of radar advantages in front-line maneuver vehicles. Already at high technology-readiness levels, these systems can achieve a mean-time-between-failure rate of several-thousand hours due to the redundant and reliable solid-state transmit/receive elements of the AESA radar. Through a process of automatic interleaving, many of these functional modes are available simultaneously to the small-unit leader and vehicle commander, vastly increasing his warfighting and force-protection effectiveness. Dr. John Reed is a senior principal engineering fellow with Raytheon Company’s network-centric systems based in McKinney, TX. He has more than 29 years’ experience in developing advanced radar systems for space-, airborne- and ground-based applications. Figure 2. Task-organizing and netting the on-the-move RF sensor assets within the maneuver element provides organic, large AO protection that moves with the force. Acronym Quick-Scan AESA – active electronically steered array APS – Active Protection System AO – area of operations BCT – brigade combat team BfSB – battlefield surveillance brigade CCTR – close-combat tactical radar C-RAM – counter rocket/artillery/ mortar EO – electro-optical FAAD – forward-area air defense RF – radio frequency RPG – rocket-propelled grenade SWaP-C – size, weight, power and cost UAV – unmanned aerial vehicle