The GeoSTAR Geostationary Microwave Sounder

A geostationary microwave sounder, capable of providing continuous all-weather monitoring of temperature, water vapor, clouds, precipitation, and wind, would add tremendously to our ability to observe and predict dynamic atmospheric phenomena, such as hurricanes and severe storms, monsoonal moisture flow, atmospheric rivers, etc. Such a sensor is now feasible, enabled by technology that has been developed at the Jet Propulsion Laboratory (JPL). The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR), is essentially an “AMSU in GEO”, providing similar measurements as are now obtained with AMSU (and ATMS) but every 5-15 minutes instead of every 12 hours and covering an entire hemisphere instead of a narrow swath. GEO orbits are almost 50 times higher than the LEO orbits that current microwave sounders operate from, and the corresponding scaling of aperture size required to maintain spatial resolution had stymied the development of such a sensor for many decades. The aperture synthesis approach implemented with GeoSTAR finally overcomes that obstacle, made possible with new technology that has been developed at JPL.