Taking stock of the NSF CASA Engineering Research Center at Year 8

Current approaches to operational weather observation are based on the use of physically large, high-power, long-range radars that are blocked from viewing the lower part of the troposphere by the Earth's curvature. The NSF Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (aka, "The CASA project") is advancing an alternate approach based on the use of dense networks of small X-band radars. Spaced tens of kilometers apart, such networks overcome the Earth curvature problem and sample the full vertical depth of the atmosphere. The radars utilize 1-m antennas and transmitters having only tens of watts of transmitter power; the small size and low power of these radars enables them to be deployed in large numbers (eg, several thousand across the USA) atop cellular communication towers, rooftops, and other elements of the infrastructure. Such networks have the potential to provide observing capabilities fundamentally beyond the operational state of the art while simultaneously satisfying the needs of multiple types of end users who use radar-related products in their decision-making. Potential improved capabilities associated with this technology include: low-altitude/boundary-layer coverage, sub-kilometer spatial resolution, rapid update times, multi-Doppler retrievals of vector winds, and the potential for detecting and tracking low-altitude aircraft that can't be seen by today's radar networks.

The cost to deploy and operate such networks includes both the up- front cost of the radars and their associated communication and computation infrastructure and the recurring costs to maintain the systems, buy or rent land and space on towers/rooftops, and provide for data communication between the radars, operations and control centers, and users. These costs, in addition to numerous technological and system-level tradeoffs, need to be balanced to ultimately develop an effective system design. If such an approach can be realized cost effectively, then this technology offers the potential to supplement -- or perhaps replace -- the widely spaced networks of physically large high-power radars in use today.

CASA was chartered by NSF as a 10 year Engineering Research Center in 2003. Efforts to date have centered on engineering design, construction, field deployment, and operation of test bed networks that support proof-of-concept studies related to the dense network concept. This paper takes stock of the CASA project at the time when the center is transitioning from an emphasis on engineering design, construction and testing, to a time where the emphasis is on exploitation and commercialization of the concept and its component technologies. We summarize the accomplishments to date related to proving the dense radar network concept with our fielded test beds; we discuss the status and roadmaps for the key enabling technologies; we present the center's results and plans for demonstrating cost/benefit of the technology and building the market to support its ultimate utilization in the civil infrastructure. We also share recent peer review assessments of the strengths, weaknesses, opportunities, and threats of both the CASA center and its concept of dense networks of small radars for improved safety and security in the civil infrastructure.