Frequently updated temperature and moisture data are critical to high-quality forecasts of weather, particulary hurricanes, floods, and other high-impact events. For many years, satellites in low Earth orbit have routinely gathered profiles of temperature, water vapor, and the amount of liquid water within clouds using microwave spectrometers and infrared sounders. Infrared sounders can be used in geostationary orbit to enable more frequent regional observations, although their performance is limited by clouds and precipitation. Limits on microwave technology have thus far kept these spectrometers from accessing the vantage point of geostationary orbit to enable more frequent observations under all weather conditions.
PATH will provide the first geostationary platform for a microwave spectrometer and infrared sounder in tandem. The mission will analyze temperature and water vapor in three dimensions, as well as sea surface temperature and precipitation. Data will be gathered every 15 to 30 minutes in both clear and cloudy conditions. PATH will lead to more accurate weather forecasts through greatly improved models of the atmosphere's lowest kilometer and the processes that shape clouds, rainfall, and snowfall. The frequently updated observations of wind speed and sea surface temperature will increase the accuracy of hurricane track, intensity, and storm surge forecasts. Water vapor and rainfall data will enhance flood prediction.
A geostationary orbit will allow PATH to carry out sampling that would otherwise require an impractically large constellation of satellites. A platform in mid-Earth orbit is another possibility; however, additional instrument development would be needed for this option.