An Airborne ASTER Simulator (AAS) acquired thermal infrared (TIR) data over the Cuprite, Nevada, and Valencia, California, areas in the USA in November 1992. The Cuprite tests demonstrated the AAS can discriminate surface geology emissivity features in arid regions. Silicate and non-silicate regions were easily distinguished; silicified and opalized lithologies were identified from decorrelation-stretch images. The AAS results agree qualitatively with earlier test data collected by NASA's Thermal Infrared Mapping Spectrometer (TIMS) and field spectrometers. Temperature differences between two lakes in the Valencia data agreed closely with ground-truth measurements. The authors' preliminary results indicate the AAS will be useful for remote sensing studies of geological materials. Following tests in 1993, the AAS may be available for investigator-initiated projects in the USA, Japan, and other countries.<<ETX>>