SOIL-MOISTURE AND RAINFALL ESTIMATION OVER A SEMIARID ENVIRONMENT WITH THE ESTAR MICROWAVE RADIOMETER

The application of an airborne electronically steered thinned array L- band radiometer (ESTAR) for soil moisture mapping was investigated ove r the semiarid rangeland Walnut Gulch Watershed located in southeaster n Arizona. During the experiment, antecedent rainfall and evaporation were very different and resulted in a wide range of soil moisture cond itions. The high spatial variability of rainfall events within this re gion resulted in moisture conditions with distinct spatial patterns. A nalysis showed a correlation between the decrease in brightness temper ature after a rainfall and the amount of rain. The sensor's performanc e was verified using two approaches. First, the microwave data were us ed in conjunction with a microwave emission model to predict soil mois ture. These predictions were compared to ground observations of soil m oisture. A second verification was possible using an extensive data se t collected the previous year at the same site with a conventional L-b and push broom microwave radiometer (PBMR). Both tests showed that the ESTAR is capable of providing soil moisture with the same level of ac curacy as existing systems. ESTAR instruments have the potential to sa tisfy application data requirements from spaceborne platforms.