This data set contains several parameters measured for the Soil Moisture Experiment 2002 (SMEX02). The parameters include soil moisture, temperature, conductivity, and salinity. 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 network of Vitel Hydra Probes that were located near the flux towers ... installed in the study area. 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.