Remote Sensing of soil moisture using the active and passive L & S bands on the PALS (Passive-Active L and S) sensor is presented. In this paper, we attempt to combine the capability of the active sensor to detect changes in roughness and vegetation characteristics coupled with the passive sensor capability to detect soil moisture and surface temperature changes. We have used the data set developed by the Jet Propulsion Laboratory during the Southern Great PLains (SGP-99) field experiment in Chickasha Oklahoma. Statistical and physical regressions between model output, aircraft observations and in-situ data are presented. In addition, radiative transfer modeling and scattering models have been used to simulate the instrument observations. The combination of active and passive data offers a powerful tool to observe soil moisture.