Initial Implementation of Adaptive Scanning on the ATD Phased-Array Radar

The Advanced Technology Demonstrator (ATD) at the National Severe Storms Laboratory is the first large-scale, S-band, dual-polarization, active, electronically scanned phased-array radar (PAR) specifically designed for weather observation. Since becoming operational in 2021, the ATD has been instrumental in proving the viability of integrating phased-array and dual-polarization radar technologies. Our success in achieving reliable and consistent polarimetric calibration has facilitated the collection of a remarkable number of data cases that illustrate how rapid-update polarimetric radar data can improve weather observations.

Designing scan strategies with rapid volumetric updates typically involves accepting degradations in data quality and/or volumetric coverage. That is, the total scan time may be reduced by using shorter observation times for the beams in the scan (e.g., by reducing the number of radar pulses per dwell), by reducing the number of beams in the scan (e.g., by reducing the number of elevation cuts in a PPI scan), or by a combination of both. With conventional scanning, the tradeoffs between update time, data quality, and volumetric coverage are built into the design of each scan strategy and cannot be changed in real time. Conversely, adaptive scanning uses real-time observations and users’ needs to redefine the scan strategy on the fly, allowing the radar to use available resources in more impactful ways. While adaptive scanning has been implemented on radars with dish antennas, PAR’s beam agility is key to unleashing the full potential of adaptive scanning.

The application software on the ATD was recently upgraded with a framework for adaptive scanning. In this framework, the signal processor produces additional information from observations at each scan beam (e.g., detecting the presence of significant weather returns), and this information is used by an adaptive scanning algorithm to issue adaptive scanning commands to the radar scheduler (e.g., disabling a scan beam with no significant weather returns). The radar scheduler processes these adaptive scanning commands in real time to change the properties or the sequence of scan beams being scheduled (e.g., removing the radar task corresponding to a disabled scan beam from the radar schedule). The initial implementation of the adaptive scanning framework on the ATD includes an algorithm for adaptive focused observations. The goal of this algorithm is to reduce the total scan time without sacrificing data quality or meaningful volumetric coverage. To reduce the scan time, the algorithm disables scan beams for regions with no significant weather returns. Scan beams with significant weather returns, and beams in a neighborhood around it, maintain the original acquisition parameters. Disabled beams are periodically re-enabled (with acquisition parameters tailored for speed and detection) to maintain full volumetric surveillance as new storms initiate or existing ones enter the radar’s scanning volume. This presentation will include results from our initial implementation of adaptive scanning on the ATD and will describe our plan for implementing more complex adaptive scanning algorithms in the future.