Progress in developing a geostationary microwave sounder

In its 2007 Earth Science Decadal Survey the National Research Council recommended that NASA develop the Precipitation and All-weather Temperature and Humidity (PATH). The objective is to place a microwave atmospheric sounder on a geostationary platform and use it to study rapidly evolving high-impact weather that is not adequately observed with current satellite systems. Atmospheric processes related to the hydrologic cycle, such as precipitation, cloud formation and transport of moisture, are also of high priority. Infrared-based observing systems are not able to penetrate clouds, and microwave-based radiometers and radars have therefore become the mainstay of cloudy and severe-weather satellite sensors. This has worked well on low-earth-orbiting (LEO) satellites, but with typical revisit times of 12 hours at best single satellites cannot capture rapidly evolving events. That requires geostationary (GEO) satellites or a large constellation of LEO satellites. Current and planned GEO satellites, including the upcoming GOES-R, only carry infrared radiometers, since microwave sensors have not been feasible due to the large aperture required to attain useful spatial resolution from such distant orbits. PATH will overcome that obstacle by deploying a microwave sounder based on an “array radiometer” approach developed at the Jet Propulsion Laboratory. First conceived of in 1998, a Synthetic Thinned Aperture Radiometer (STAR) design and the technology required to implement it - GeoSTAR - have been developed at the Jet Propulsion Laboratory under the NASA Earth Science Technology Office's Advanced Component Technology program and Instrument Incubator Program. While the National Research Council classified PATH as a third tier mission due to immature technology, that has now been addressed, and the PATH mission can proceed when the current GeoSTAR IIP task is completed in early 2015. In the meantime, a low-cost pre-PATH mission addressing a subset of the PATH objectives can be implemented now. We discuss the basis for PATH and the developments that have taken place to enable the PATH mission as well as the low-cost GeoStorm mission that has been proposed under the Venture program. GeoStorm is a severe-storm observatory operating as a hosted payload on a commercial communications satellite. Its science focus is on rapid intensification processes that dominate tropical cyclones, mesoscale convective systems and extratropical cyclones.

Copyright 2014 California Institute of Technology. Government sponsorship acknowledged.