Advanced Tactical Targeting Technology 1. Good afternoon ladies and gentlemen. I'm Beth Kaspar and today I would like to tell you about a DARPA technology program that has current relevance to our warfighters. Operations in Kosovo all point to the need for an improved SEAD capability. I will tell you about our Advanced Tactical Targeting Technology, or AT3, program. I will describe AT3's importance, its goals and factors bearing on its concept and implementation. 2. AT3 will demonstrate technologies to counter enemy surface-to-air threats. These threats are tough because of the difficulty in accurately finding them quickly enough to engage before they pick up and move. Accurate and timely surface to air missile system geo- location are major performance considerations so that our warfighters can employ their shoot-to-coordinate precision guided munitions effectively. 3. This is the goal of AT3 to develop and demonstrate technologies for a cost effective TARGETING system for lethal suppression of enemy air defenses, or SEAD. Note that I emphasize that this is a TARGETING demonstration program. We are not developing a new weapon. 4. The AT3 concept employs passive, RF, multiplatform geolocation techniques; namely, Time Difference of Arrival (TDOA) supplemented with other techniques for ambiguity resolution. The system measurements will be quick and accurate, unlike passive single platform target location techniques. This enables us to determine shoot-to-target coordinates despite target emitter shutdown or mobility. AT3 receiver/processor equipment will be carried by various, nondedicated aircraft. The aircraft may be manned or unmanned. In the cartoon, the lead aircraft detects, classifies and selects a target emitter. The lead then broadcasts requests including target type and RF parameters to other collectors in the vicinity. The responding collectors automatically tune their receivers. They then relay pulse times of arrival, the received RF and other parameters, plus their own position and velocity. A processing node, in this case the aircraft at "4", measures the multiple TDOAs and frequency differences of arrival reports in order to resolve ambiguities, precisely locate and target the emitter. 5. AT3 will employ 2 primary location techniques. The TDOA techniques, which are shown on the first panel at left, require three or more platforms with coordinated measurements. Each collector measures the Time of Arrival of an emitted pulse. For each pair of collectors, for example, A and B in the figure, the Time Difference of Arrivals correspond to possible locations along a hyperbolic curve. With three collectors, the curves intersect at the actual emitter location. • This intersection, however, depends on each time difference measurement being taken on the same transmitted pulse. If different transmitted pulses are used to measure TDOA, then we have a situation such as shown in the second panel. Here, a pulse received by Collector B has been associated with an earlier pulse received by Collector C. This false TDOA corresponds to the dashed curve, which intersects at erroneous "ghost" locations. • Integrating additional techniques, for example, Frequency Difference of Arrival or angle of arrival, can assist in eliminating ghost solutions and enhance measurement accuracy. The third panel shows how two platforms can resolve location using TDOA plus FDOA. The difference in frequency received by Collectors A and B corresponds to possible emitter locations on the red locus. This will intersect with the TDOA curves at the correct emitter location, but will not intersect at the "ghost' locations. 6. AT3 achieves flexibility and robustness not only through opportunistic use of platforms, but also through use of various target acquisition modes. • In the tip and tune mode, any platform that detects an emitter can initiate a request for a cooperative collection, with no prior coordination. Tip and tune is the most responsive mode. It can be used if there was no prior knowledge of an emitter being in the area. • Good self-navigation and knowledge of enemy electronic Order of Battles enables preplanned coordinated emitter scan tables to be employed by the AC collectors. This scheduling would be part of pre-mission planning. Alternatively, the cooperative collections could be planned to occur when specific way points are passed. While this is less flexible than tip and tune, it can ensure cooperative collections are made against suspected high priority emitters. The final mode is coordinated cue. This is where a collector outside the AT3 network can, using a coordinated Link 16 message format, tip off the AT3 network to make a cooperative collection against a high priority emitter. 7. This chart illustrates the importance of achieving a small target location error, or TLE, if generic shoot-to-coordinate weapons are to be used for lethal SEAD. Now with the smaller TLEs, AT3 provides both submunition area-weapons as well as unitary-warhead PGMs can be used effectively with high probability of kill against surface-to-air-missile threats. 8. This chart shows a notional block diagram for an AT3 System. The receiver front end must combine sensitivity with a large dynamic range, so AT3 collectors may make signal measurements on main lobe, side-lobe and back-lobe signals. The signal processor must acquire, associate, deinterleave, and classify signals. It must respond to controller instructions for synchronized dwells and for making TDOA/FDOA measurements. The controller must initiate a synchronized dwell on a newly detected signal, manage the geolocation process, and also manage data link traffic with other AT3 platforms. Good clocks assure data alignment and time synchronization. Finally, collectors must locate themselves accurately. Precision GPS/INS assures that. 9. These are the five key technical challenges that we face in AT3. I will step past common pulse for now, as I will discuss it on the next chart. We want to perform the AT3 function opportunistically in emitter sidelobes. Accordingly, we need well calibrated receivers with high dynamic range. We will also need a quick reacting tactical network with access management to minimize latencies and data compression to reduce traffic load. We need resilience to multipath. Finally, one of AT3's main efforts is in demonstrating geolocation algorithms which provide small TLEs. 10. The first processing challenge is for all collectors to identify a common set of emitter associated pulses. TDOA geolocation requires measurements be resolved to the same pulse train radiating from the target. This will require the use of shared sample pulse data and templates between collectors, so each collector is assured of measuring the same set of associated pulses. AT3 will utilize advances in digital signal processing, data fusion, and space-time reference technologies to solve these problems. Other challenges cover a broad range of signal processing: this includes recognizing, associating, and deinterleaving pulse signals, making precise time difference and frequency difference measurements coherently on weak signals, and compressing/decompressing sampled signal data so it can be transmitted with low latency over narrow band links. The AT3 tactical emitter collector packages must be affordable with low host burden to accomplish the necessarily wide spread deployment on theater tactical airborne assets. 11. Related to common pulse, and equally essential to achieving precise TDOA/FDOA, is the common registration of all measurements with the collector's position, velocity, and time. This chart cites quantitative goals for PVT, or 7-D Registration. AT3 will be developing detailed error budgets defining what is required in the way of common registration to support the program goals. TDOA/FDOA geolocation will require that all signal measurements be precisely registered in a common reference frame. Space-Time Reference system technologies for precise, real- time alignment of collector location, velocity vector, and timing will be used to meet this need. The GPS Guidance Package (GGP) is an integrated, precision GPS/INS. A precision clock can assist in providing the needed 7D (time, position and velocity) registration of the AT3 measurements. 12. Critical to achieving the full dynamic range desired is the analog to digital converter in the receiver. This chart represents the current state of the art of ADCs. It shows that for AT3 to achieve its maximum goals, advances in ADCs will be required. For now, the DARPA program focus will be on detecting and prosecuting threats in the forward 180º of the emitter. The follow-on program could expand the detection window as better ADCs come on the market. 13. This chart exhibits some of the time line activity and coordination required within an AT3 collection network. AT3 must manage its processing load distribution over a low information rate broadcast type communication network in order to achieve rapid response times and control data latency. The goal is to complete the AT3 functions and detect a target within seconds. • The time line activity, coupled with the nature of the Link 16 data link, points out the challenging nature of network management. This management includes collector access control and data exchange associated with doing common pulse and TDOA/FDOA geolocation. Through system parametric trades and system simulation, we expect to identify and determine the communication subsystem delay versus throughput performance which are required by the AT3 goals. 14. AT3 plans to use JTIDS Link 16. This chart shows a notional mapping of the information AT3 must pass between collectors into the Link 16 world. Preliminary assessment has established that one net dedicated to AT3 should be sufficient. But to meet AT3 goals for timeliness, attention must be paid to data latency and to data compression. Notes: Link 16 Capacity: 128 Nets; current JTIDS radio operates on 4 Nets Single Net Capacity: Max 54 KBPS High 19 KBPS Typical 9 KBPS A/J 2.4 KBPS 15. To ensure that data is available to support the timeline, data compression will be necessary. Passing over Link 16, sampled pulse data for coherent processing between collectors may require 3 to 1 or better data compression. Means of achieving this are being investigated, including wavelets. For sampled pulses which do not require coherent processing, careful selection of pulse descriptor words provides an even higher degree of data compression. 16. AT3 is a DARPA led effort with participation by the Air Force Research Laboratory. The AT3 prime contractors are Lockheed Martin Federal Systems in Owego, NY and Raytheon TI Systems Company in Tucson, AZ. This is a two-phase program with Phase 1 culminating with critical design reviews in April 2000. Operational User participation will be extensive throughout the program to insure the revolutionary new CONOPS are viable. The transition strategy is based on retrofit to existing aircraft with minimum vehicle modification either via existing pod retrofit or through utilization of already installed antenna apertures. Insertion into new vehicles such as JSF will be pursued. As appropriate, other platforms will be investigated. Expected application transition customers include the Air Force and Navy. 17. The AT3 effort requires employing advanced multi-ship TDOA/FDOA signal processing and geolocation techniques capable of operating in dense threat environments. Exploiting a very robust, precise P, V, T, and F cross collector reference subsystem offers new and exciting possibilities for the needed processing algorithms. Additionally, AT3 processing must be prepared to mitigate possible multipath effects on geolocation accuracy. Given the essentially horizontal, coplanar location of the AT3 collectors, the vertical dilution of precision (VDOP) will be large. Digital terrain elevation data (DTED) will be combined with AT3's good horizontal location performance to improve the vertical accuracy in threat geolocation. AT3 digital receivers demand high throughput signal processing. Designs to date have depended upon custom modules for the receivers. If software configurable chip sets were available which performed the basic AT3 signal processing functions, an AT3 or similar high performance, high throughput digital receiver could be constructed using software to configure the basic building block function chips. I can summarize my talk today with three points. AT3 is a DARPA effort to enable responsive, efficient precision targeting of threat air defense units; to bridge the gap from reactive suppression to preemptive destruction; and to exploit tactical platforms including fighters and UAVs for SEAD applications.