GeoSTAR - a synthetic aperture approach for a geostationary microwave sounder

GeoSTAR is a new microwave atmospheric sounder under development, with capabilities similar to sensors now operating on low Earth orbiting weather satellites. GeoSTAR is intended for deployment in geostationary orbit - where it complements future infrared sounders and enables all-weather temperature and humidity soundings and rain mapping. The required spatial resolution of 50 km at 50 GHz dictates an aperture of 4 meters or more, which is difficult to achieve with a real aperture system. GeoSTAR is instead based on a synthetic aperture imaging approach. Among the advantages of such a system are that there are no moving parts, and the size of the aperture is easily expandable to meet future needs. A ground based prototype of GeoSTAR is currently under development in an effort led by the Jet Propulsion Laboratory. We describe the measurement and calibration approach, system design, and selected technology elements.