Aperture synthesis for passive microwave remote sensing: The electronically scanned thinned array radiometer

Aperture synthesis is applied to passive microwave remote sensing of the earth in an effort to attain high resolution images at low microwave frequencies. An L-band (1.4 GHz) synthetic aperture radiometer, dubbed the Electronically Scanned Thinned Array Radiometer, is tested and calibrated. The instrument is modeled after radio telescopes, and utilizes a thinned array of correlation interferometers to measure the Fourier Transform of the Brightness temperature image. The antenna hardware of such an array is reduced by comparison with real aperture antenna systems, which renders this technique relevant to future spaceborne remote sensing applications that require high resolution. In particular, it is the scientific applications at L-band, including the spaceborne remote sensing of soil moisture and ocean salinity, which have motivated this research. Aperture synthesis concepts are developed and applied to the theoretical ESTAR system in chapter II. Chapter II also includes a description of the prototype which was designed constructed at the University of Massachusetts. Practical calibration algorithms are developed in chapter III, and the synthesis technique is refined in chapter IV to reduce side lobes. Chapter V presents the first known images by this class of remote sensing radiometer, and the concluding chapter suggests avenues for future research