The SMOS Validation Campaign 2010 in the Upper Danube Catchment: A Data Set for Studies of Soil Moisture, Brightness Temperature, and Their Spatial Variability Over a Heterogeneous Land Surface

The Soil Moisture and Ocean Salinity mission has been launched by the European Space Agency (ESA) in November 2009. It is the worldwide first satellite dedicated to retrieve soil moisture information at the global scale, with a high temporal resolution, and from spaceborne L-band radiometry. This novel technique requires careful calibration, validation, and an in-depth understanding of the acquired data and the underlying processes. In this light, a measurement campaign was undertaken recently in the river catchment of the upper Danube in southern Germany. In May and June 2010, airborne thermal infrared and L-band passive microwave data were collected together with spatially distributed in situ measurements. Two airborne radiometers, EMIRAD and HUT-2D, were used during the campaigns providing two complementary sets of measurements at incidence angles from 0° to 40° and with ground resolutions from roughly 400 m to 2 km. The contemporaneous distributed ground measurements include surface soil moisture, a detailed land cover map, vegetation height, phenology, and biomass. Furthermore, several ground stations provide continuous measurements of soil moisture and soil temperature as well as of meteorological parameters such as air temperature and humidity, precipitation, wind speed, and radiation. All data have undergone thorough postprocessing and quality checking. Their values and trends fit well among each other and with the theoretically expected behavior. The aim of this paper is to present these data which may contribute to potential further studies of soil moisture, brightness temperature, and their spatial variability. The presented data are available to the scientific community upon request to ESA.