A large-antenna microwave radiometer-scatterometer concept for ocean salinity and soil moisture sensing

Microwave radiometry and scatterometry are established techniques for surface remote sensing applications. Some applications, such as measurement of sea surface salinity (SSS), sea surface temperature (SST), and soil moisture, require low frequency observations (∼6 GHZ and below) for good sensitivity, and sensors with large antennas to achieve adequate spatial resolution. Potentially, benefits can be obtained by observing simultaneously with passive and active channels, at similar frequencies, viewing angles, and spatial resolutions, making use of the complementary information contained in the emissivity and backscattering signatures of land and ocean targets. In this study, the authors investigate a concept for combined passive and active multichannel sensing with high spatial resolution, high measurement sensitivity, and wide swath for frequent global coverage. The system consists of a lightweight, relating, deployable mesh antenna with offset feeds. The system specifications are designed primarily for the measurement of sea surface salinity, since this application drives the precision and calibration requirements and, like soil moisture, is a science measurement for which no spaceborne capability currently exists. Demonstration of a capability for sea surface salinity will enhance the potential of this large antenna concept for other applications such as soil moisture and, by including higher frequencies, high resolution measurements of ocean winds, precipitation, sea-surface temperature, and sea-ice.