Airborne Phased-Array Radar (APAR) Trade Study Results

The University Corporation for Atmospheric Research (UCAR) in coordination with the National Center for Atmospheric Research (NCAR) proposes the development of a next generation Airborne Phased Array Radar (APAR) for meteorological observation and characterization of extreme weather phenomena. Data collected and results using the APAR platform will lead to better forecasting and estimation of heavy precipitation and potential economic impacts for the nation. APAR is intended to be a dual-polarized active electronically scanned array (AESA) consisting of several thousands of individually controlled radar elements attached to the National Science Foundation (NSF)/NCAR C-130 scientific research aircraft. A preliminary set of requirements for the APAR antenna system was generated by the NCAR staff and provided to potential industry partners. UCAR funded Ball Aerospace to review and analyze the requirements and to assess the design considerations on the basis of technical maturity, cost achievability, system fault tolerance and system performance. The goal is to help develop a system that can be both manufacturable and cost effective, and that will remain scientifically relevant over the intended lifetime of the APAR system.

Requirements critical to the mission performance, such as Integrated Cross Polarization Ratio (ICPR) and Integrated Sidelobe Levels (ISL), were analyzed in detail, including failure and tolerance analysis as well as degradation over the defined scan volume. Reasonable requirements were developed to affordably achieve maintain overall APAR mission success. In addition, digital beamforming (DBF) topologies were analyzed based on balancing performance with cost, size, weight, and power (C-SWAP), resulting in the recommendation of a 1-D hybrid DBF architecture that maximizes performance. This paper outlines these analyses, our results given the system constraints, and recommendations on modifications to the requirements that best balance the goals of affordability, robustness, maintainability and scientific performance in an APAR antenna system.