Airborne Phased Array Radar (APAR)

Implementing APAR: The Next Era of NSF NCAR’s Airborne Radar

The purpose of the Airborne Phased Array Radar (APAR) is to provide a leap forward as the scientific community’s next generation airborne weather radar. The ambitious plan originally placed four C-band PAR panels in strategic locations on the NSF NCAR EC-130Q aircraft to provide significantly advanced, high-resolution volumetric observations of high impact weather systems, such as hurricanes, tornadoes, derechos, atmospheric rivers, and severe winter storms and blizzards. NSF NCAR is committed to the advancement of this state of the art weather radar concept, while implementing a new flexible architecture approach that facilitates enhanced capabilities across both research and operational communities.

Scientific and Operational Motivation

In a recent study by NOAA, billion-dollar weather and climate related disasters are becoming more frequent in the United States, with such events affecting the nation on an average of nine times per year between 1980-2024. However, over the past five years (2020-2024), the average number of such events jumped to 23. Providing critical observations to both researchers and forecasters from an airborne weather radar system allows specific operation in hard-to-reach environments, such as over the oceans or highly variable terrain. Operating an airborne weather PAR utilizes advanced technology to enhance our understanding of mechanisms that intensify severe weather hazards and improve our forecast accuracy to assist decision-makers in preparation for and mitigation of associated damage.

Bridging the Gap

The Electra Doppler Radar (ELDORA) was a previously available and community supported airborne weather radar for monitoring significant weather events but was retired from service in 2013. Without this instrument, the resources for collecting airborne observations are stretched to other agencies with different obligations and requirements. Continuing to push for this advanced weather radar technology is necessary to fill the current gap in observing capabilities for the research community.

Flexible C-130 Architectural Approach

NSF NCAR uses its EC-130Q aircraft for various scientific studies and field campaigns. The C-130’s versatility makes it ideal for operating a PAR for observing significant weather events because of its unique ability to fly in and around severe weather. Determining the best implementation and installation options for a future airborne PAR requires creative architectural collaboration. Analysis is underway of “Commercially Off The Shelf” (COTS) options for mounting one or multiple PAR’s on the NSF NCAR C-130 without modifying the main aircraft structure to support an adaptable infrastructure to test airborne PAR instruments. Additionally, NOAA has initiated the process to transition from their current WP-3D to the C-130 aircraft. NSF NCAR’s updated, C-130 agnostic approach for testing airborne PAR promotes activities that enhance cross-agency partnerships.

APAR options Airdyne and paratroop door solution — Several current and minimally invasive solutions already exist on the market, including a pod-and-arm solution supported by Airdyne (left) and conformal paratroop door solution supported by Marshall (right).

Collaboration is Key

Whether through support from internal and external agencies, expertise within the scientific community, or partnership with the private industry sector, the continuation of the airborne weather PAR program is dependent on strong collaboration. Finding ways to connect resources and knowledge along the new path is vital for ensuring that NSF NCAR can close the airborne weather radar gap and provide such a vital facility to the research community.

Forging Ahead

The development team continues to achieve significant milestones in software design, scientific simulation, and infrastructure improvement. These advancements serve as a launching pad for ongoing activities that create opportunities for a future airborne PAR:

Optimization of size, weight, and power requirements for reduced implementation risk while meeting scientific requirements
Leveraging recent COTS radar technology
Ongoing studies for risk reduction and shaping the future of airborne weather radars
Airborne Test-bed Feasibility Study for technology maturation evaluation and efficient model development to assess capabilities of community-supporting experimental RF instrumentation
Integrated PAR Digital Twin to define optimal connections between engineering and science requirements
Multi-frequency Implementation Study using the APAR Observing Simulation, Processing, and Research Environment (AOSPRE) to diagnose trade-offs in radar operation and scientific analysis

APAR Placement Options — An airborne feasibility study will determine observing capabilities of different PAR placement options on the C-130. This example highlights the pod-and-arm solution.

MSRI-2 Airborne Phased Array Radar (APAR) →