The core of the 1997 experiment involves the deployment of the L-band Electronically Scanned Thinned Array Radiometer (ESTAR) for daily mapping of surface soil moisture over an area greater than 10,000 km2 and a period on the order of a month. The region selected for investigation is the best instrumented site for surface soil moisture, hydrology and meteorology in the world. This includes the USDA/ARS Little Washita Watershed, the USDA/ARS facility at El Reno, Oklahoma, the ARM/CART central facility, as well as the Oklahoma Mesonet. The region covered by the experiment is 34.5 to 37 North latitude and 97 to 99 West longitude. The aircraft mapping took place over the period 18 June to 18 July 1997. This dataset presents brightness temperature images from the Electronically Scanned Thinned Array Radiometer (L band passive microwave radiometer).