Notice to Data Users: The documentation for this data set was provided solely by the Principal Investigator(s) and was not further developed, thoroughly reviewed, or edited by NSIDC. Thus, support for this data set may be limited. This data set contains radar soil moisture measurements taken over the Soil Moisture Experiment 2003 (SMEX03) regional study areas in Oklahoma, USA. The Airborne Synthetic Aperture Radar (AIRSAR) instrument was mounted on a DC-8 aircraft that flew over the area six days during the study period.