This paper summarizes performance analyses of an MPAR design using four simultaneously operating phased array faces. A major technical challenge for MPAR is the required radar timeline when a significant portion of the coverage volume is filled with weather. We evaluated the timeline impact as system design features and capabilities were varied, resulting in a set of proposed solutions and trades for the government to consider in defining a final MPAR system.
MPAR supports numerous scan types. The Weather Volume Scan (WVS) identifies regions of precipitation. Once weather is located, precipitation scan (PSCAN) dwells are scheduled to provide high fidelity weather products. MPAR PSCAN dwells must be completed every minute in contrast to four minutes for the current NEXRAD. This reduction in PSCAN update time is a major contributor to the MPAR timeline burden. Additionally, scans for wind shear monitoring, aircraft surveillance, and aircraft track updates are interleaved with the weather scans.
To perform the requisite functions within radar power, aperture and timeline constraints, we pose functionality that offers parallelism in the radar's operation to buy back timeline. Our solution uses multiple array faces, dual simultaneous orthogonal polarization paths, subarray-based beamforming, multiple transmit and receive beams, multiple sub-pulse waveforms, and extensive parallel signal and data processing. Broadened transmit beams and multiple simultaneous receive beams provide additional timeline efficiency. Finally, we incorporate an intelligent sensor manager that optimizes system operation and performance in dynamically changing environments.
In the absence of precipitation, MPAR provides terminal and en route aircraft surveillance, the WVS, and clear air scans (CAS), with reserved timeline. The stressing case (Fig. 3), when precipitation fills the coverage volume, requires the PSCAN and renders the WVS and CAS unnecessary. PSCAN also uses dual transmit beams for timeline savings.
Potential solutions require timeline utilization ≤100%. Cost and/or complexity increases with the number of transmit beams, the extent of azimuth oversampling, the extent of EL coverage, increased weather product accuracy, and reduced PSCAN update time. Performance relaxation should be considered in the trade space when it offers reduction in cost and/or complexity.
Table 1 summarizes potential design operating points. Compliant performance (shaded green) requires 60ยบ EL coverage, 60 s PSCAN update time and 1 m/s mean velocity accuracy. Relaxed performance is shaded yellow. Lower cost/complexity is shaded blue. Higher cost/complexity is shaded pink. Cases that exceed the PSCAN compliant update time are still less than the NEXRAD VCP-12 update time.
Our study identified factors that stress the radar timeline, and offered a number of designs that trade performance and capability as a function of system complexity and cost. A compliant solution was identified for the most demanding timeline situation. Other potential solutions offer relaxed performance/capability for sake of reduced cost and/or complexity.
Note: The views and conclusions expressed in this paper are those of the authors and not necessarily of the FAA or NOAA.
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