The Hurricane Imaging Radiometer (HIRAD) is an airborne passive microwave synthetic aperture radiometer designed to provide high resolution, wide swath imagery of surface wind speed in tropical cyclones from a low profile planar array antenna. This paper will present the array radiometer system concept and summarize its development, including multiple flight tests on NASA's Genesis and Rapid Intensification Processes (GRIP, 2010) and Hurricane and Severe Storm Sentinel (HS3, 2012) campaigns. The paper will focus on the design goals, trades, and approach for the array antenna along-track beam former. The paper presents details of the beam former design, implementation, integration approach, and measured performance. The paper concludes with a description of planned improvements for the next generation dual-polarized HIRAD antenna and the resulting impacts on the beam former design and integration.

The Hurricane Imaging Radiometer System (HIRAD) is a new airborne passive microwave remote sensor developed to observe hurricanes. HIRAD incorporates synthetic thinned array radiometry technology, which use Fourier synthesis to reconstruct images from an array of correlated antenna elements. The HIRAD system response to a point emitter has been measured in an anechoic chamber. With this data, a Fourier inversion image reconstruction algorithm has been developed. Performance analysis of the apparatus is presented, along with an overview of the image reconstruction algorithm.

A C-band four-frequency resonant stacked-patch array antenna is developed for synthetic thinned aperture radiometer measurements of hurricane force wind speeds. This antenna is being integrated into an aircraft instrument referred to as the Hurricane Imaging Radiometer (HIRAD). Details of the antenna design are presented along with antenna performance tests and laboratory measurements using a full-scale prototype array with a subset model of the HIRAD instrument.