The hurricane imaging radiometer - an octave bandwidth synthetic thinned array radiometer

The Hurricane Imaging Radiometer (HIRad) is a new airborne sensor that is currently under development. It is intended to produce wide-swath images of ocean surface wind speed and near surface rain rate in hurricanes conditions. HIRad will extend the scientific capabilities and technologies associated with two previous successful airborne microwave radiometers: the real aperture Stepped Frequency Microwave Radiometer (SFMR) and the synthetic aperture Lightweight Rainfall Radiometer (LRR). Both SFMR and HIRad are required to operate over the full C-Band octave in order to estimate precipitation levels experienced in hurricanes without saturation and to penetrate through the precipitation and estimate surface winds. Operation over an octave bandwidth was easily accomplished by the nadir-pointing horn antenna used by SFMR. However, it represents a major technological challenge for the HIRad design because it is a Fourier synthesis imager. Details of how HIRad meets that challenge are described here.