Bringing Aegis to the Littorals

By Commander Robert J. Engel, U.S. Naval Reserve

The SPY-1B radars on the Aegis cruisers Princeton (CG-59) through the Port Royal (CG-73) and the SPY-1Ds on the Arleigh Burke destroyers through DDG-90 incorporate improved resistance to electronic countermeasures, larger track files, and significantly reduced side lobes.

The new SPY-1D(V) radar system—a quantum improvement—exemplifies the Aegis tradition of evolving to meet new threats. Specifically developed to counter smaller antiship cruise missiles flying lower and faster in the littoral clutter, the system has substantially improved detection and tracking performance. It is operational at the Aegis Combat System Engineering Development Site in Moorestown, New Jersey, and has completed Navy Development and Operational Test during which fleet sailors detected and tracked live and simulated targets.

The requirement to counter such targets presented significant design challenges to increase the radar's sensitivity and sub-clutter visibility while maintaining a rapid search rate throughout the radar-coverage region. Increasing radar sensitivity in the heavy traffic and clutter of the littorals dramatically increases the number of transient detections and nuisance tracks. Processing these tracks consumes radar time, power, and computer processing resources, which leads to slower search rates, cluttered displays, and confusion. Operators waste time and energy trying to clean up their displays and track files instead of managing the data presented to them.

The SPY-1D(V) team applied new technology innovatively to modify the radar equipment and to enhance the tactical computer programs. Modifications include the replacement of the SPY-1B/D signal processor with the advanced signal processor and the replacement of the SPY-1B/D low-power radio-frequency (RF) amplifier cabinets with new simplified drivers and their power supplies. Architectural improvements enable the SPY-ID(V) computer program to shift from one UYK-43 computer to two UYK-43s and then to a commercial off-the-shelf processor when the system is introduced into the fleet.

The AN/SPY-ID(V) retains the SPYIB/D phased arrays, high-power RF amplifiers, auxiliary, and support systems.

The advanced signal processor is the heart of the technological improvements. It incorporates more than 5,000 application-specific integrated circuits on a variety of general control microprocessor modules. Twenty-six new module types have been developed for the new processor; each is the equivalent of up to 200 SPY-IB/D modules. This technology provides for a real-time programmable architecture supporting complex algorithmic calculations, equipment controls, fault detection, fault isolation and local memory operations. New algorithms are downloaded to programmable signal processor modules in real-time to conduct specific complex operations. The system incorporates a new pi-bus architecture for exchanging data within the processor and contains more than 175,000 lines of "firmware" resident in the local memory modules. This firmware provides for tremendous flexibility and adaptability to a wide variety of processing requirements.

New low-power RF amplifiers provide higher average power, lower noise, and more pulse-to-pulse, phase, and amplitude stability than did the SPY-ID.

These combinations of advancements in equipment and firmware technology led to the development of advanced radar capabilities that permit the system to fulfill its littoral warfare missions. The following highlight some of the performance improvements of the AN/SPYID(V) Radar System.

A Moving Target Indicator (MTI) enables a radar system to cancel clutter to extract moving targets masked by the clutter and to reduce the number of transient detections by reducing clutter below the noise floor. An effective MTI capability is crucial to the quality of the tactical picture presented to operators in CIC and on the track information transmitted through data links. The SPY1D(V) radar contains a number of MTI design innovations:

  • Computer-selectable MTI waveforms of two through seven pulses that provide for greater rejection of clutter and nuisance tracks under computer control. The system automatically selects the best MTI waveforms to maintain fire-control quality track on targets throughout the clutter region.
  • Wider-notch MTI that permits the rejection of nuisance tracks (birds, etc.), which are moving but clearly are not threats. The feature cancels multiple sources of clutter with different speeds such as land clutter and rain. Figure I shows the advantage of wide-notch MTI in rejecting nuisance tracks.
  • Automatic Adaptive Mode Control that permits the system to select automatically the optimum MTI search waveform for the tactical environment. This removes the MTI management burden from the radar operator and permits rapid search rates and continuous coverage.
  • Pulse-Doppler acquisition and tracking waveforms of 12 and 16 pulses that provide greater sensitivity with more clutter rejection than MTI to see selected targets in heavy clutter and chaff. This provides operators with a capability to continue to track tactically significant targets through regions of dense clutter and chaff clouds. The pulse-Doppler mode also provides for a cued-search capability from off-board sensors to support searching with pulse Doppler waveforms in regions of dense clutter.

A dual-beam search capability has been added to the radar system to maintain the rapid search coverage with the increased processing time required with the advancements in MTI. It provides the capability to search in two directions at once using opposing array faces. The search data returns are processed independently in two channels of the four-channel signal processor. Dual-beam search permits the radar system to maintain a high data rate surveillance of the radar volume in a heavy clutter and track environment. Significant changes to computer program architecture and the incorporation of advanced commercially available processors have been implemented to process the dramatically increased number of radar dwells per second.

The SPY-1D(V)'s track-initiation processor is integrated fully into the advanced signal processor with a track-while-scan process that uses the rapid horizon search rate to screen out contacts on or near the surface. Long-duration slow tracks are identified and passed to the Gun Fire Control System. The capability is being retrofitted into the SPYIB/D ships as a separate processing cabinet.

Availability and reliability are high priorities. Improvements in fault detection and fault isolation coverage within the equipment and computer programs combined with a new commercial Operational Readiness Test System make this radar the most maintenance-friendly system yet. Line-replaceable unit size distribution has been reduced and the system has fewer types of modules; a ship can carry more of the right spare parts. Development and Operational Testing with fleet sailors has confirmed these maintainability improvements.

Without compromising its traditional blue-water role—or its new littoral capabilities—the SPY-ID(V) can make a significant contribution to the Navy's Ballistic Missile Defense mission. The advanced signal processor's built-in design flexibility combined with the increased average power and waveform stability of the upgraded transmitter will enable this radar to play a major role in theater ballistic missile defense operations.

The SPY-1D(V) radar system continues the AEGIS tradition of evolving to meet the threat.

Commander Engel is the Program Manager for the Engineering Development Model-5 program at Lockheed Martin Electronic Systems in Moorestown, New Jersey—a prototype effort to move the Aegis weapon system computer program to commercial off-the-shelf processors. He was the Integration and Test Manager for the AN/SPY-1D radar system.



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