Initial Evaluation of Single-Face Rotating PAR Concepts of Operations at the National Weather Radar Testbed

The Advanced Technology Demonstrator (ATD) installed at the National Weather Radar Testbed (NWRT) in Norman, OK is the first full-scale, S-band, dual-polarization, active, electronically scanned phased-array radar (PAR) designed for weather observations. Leveraging prior investments, the ATD provides a flexible and cost-effective means to demonstrate some of PAR’s unique capabilities that could be leveraged to meet National Oceanic and Atmospheric Administration’s (NOAA) expanded radar requirements in support of improved weather warnings. NOAA’s evaluation of potential alternatives for the next operational radar system includes the concept of a single-face rotating PAR (RPAR) architecture, seen as an interesting compromise between affordability and capabilities. Although initially not intended for continuous rotation, the ATD antenna is strategically placed atop an azimuthal turntable, allowing periodic repositioning to orient its broadside-relative ±45° azimuthal field of view to the most relevant sector. While this infrastructure offers the possibility of initial proof-of-concept RPAR evaluations, the creation of a radar scheduler tailored to RPAR operations presents significant challenges.

Unlike stationary-antenna operations, which exclusively use electronic beam steering, RPAR operations combine mechanical and electronic beam steering. Moreover, the sequencing of beams in an RPAR scan and the electronic steering necessary to direct the radar beam in each scan direction must be determined in real time due to the antenna’s ever-changing mechanical position during rotation. Additionally, executing RPAR concepts of operations requires more intricate scheduling mechanisms because the continuous rotation of the antenna results in a constantly changing azimuthal field of view, and scan execution cannot be assumed to be synchronized with this rotation. The complex interplay of these factors renders the development of a real-time RPAR radar scheduler that supports advanced concepts of operations notably challenging.

In this work, we describe the development of a new radar scheduler for the ATD, designed to support RPAR experimentation. We also summarize how this capability is being used to evaluate various concepts of operations that effectively combine the PAR antenna rotation with its unique ability to steer the radar beam electronically. The initial RPAR concepts of operations supported by the new ATD scheduler range from simple round-robin scheduling involving multiple scans to sophisticated scenarios that interleave PPI and RHI scans. Finally, we discuss a plan for continuous experimentation and refinement of this capability. This approach will enable meaningful and timely evaluations of some of the advantages and limitations associated with utilizing the RPAR architecture for weather observation.