Preparing for the PATH mission

The goal of the Precipitation and All-weather Temperature and Humidity (PATH) decadal-survey mission is to place a microwave atmospheric sounder on a geostationary platform, with a science focus on rapidly evolving high-impact weather, such as hurricanes, that is not adequately observed with current satellite systems. Observing atmospheric processes related to the hydrologic cycle, such as precipitation, cloud formation and transport of moisture, is also a 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 satellites, but with typical revisit times of 12 hours at best they cannot capture rapidly evolving events. That requires geostationary satellites. Current geostationary satellites only carry infrared radiometers, and microwave sensors have not been feasible due to the large aperture required to attain useful spatial resolution from such distant orbits. PATH will fill that gap 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 under the NASA Earth Science Technology Office's Advanced Component Technology and Instrument Incubator Programs. While the National Research Council classified PATH as a third tier mission due to immature technology, that has now been addressed, and a full PATH mission can proceed when the current GeoSTAR IIP task is complete in 2014. In the meantime, a low-cost pre-PATH mission addressing a subset of the PATH objectives could be implemented now under the Venture program. We discuss the basis for PATH and the developments that have taken place to enable the PATH mission.

Copyright 2012 California Institute of Technology. Government sponsorship acknowledged