This data set combines data for several parameters measured for the Soil Moisture Experiment 2002 (SMEX02). The parameters include bulk density, gravimetric and volumetric soil moisture, and surface and subsurface soil temperature. This study was conducted during June and July 2002 in the Walnut Creek watershed in south-central Iowa, USA. Data were collected in crop fields, using a variety of ... methods and sensors (manual soil samples for bulk density and gravimetric soil moisture data, infrared pyrometers for surface and subsurface soil temperature, and impedance probes for volumetric soil moisture). Data are provided in ASCII text files, and are available via FTP. These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.