EVALUATION OF THE ERS-1 SYNTHETIC APERTURE RADAR CAPACITY TO ESTIMATESURFACE SOIL-MOISTURE - 2-YEAR RESULTS OVER THE NAIZIN WATERSHED

One of the possible applications of satellite radar remote sensing is to estimate surface soil moisture. To evaluate the capacity of ERS 1/s ynthetic aperture radar (SAR), a European Space Agency (ESA) pilot pro ject has been set up. The test site is a-small agricultural watershed situated in the central part of French Brittany. During 1992 and 1993, almost all possible SAR images were acquired together with two types of ground truths: intensive ground measurements during 14 field campai gns and point automatic measurements over the entire period. From the comparison of those ground truth data with the ERS 1 images, the follo wing results are obtained. On a field scale the relation between the r adar signal and the surface soil moisture depends strongly on the type of culture: Correlation is poor for the different cultures except for wheat. On a basin scale, it is shown that during the period of low ve getation density, there is a linear correlation between the mean radar data and the point automatic measurements. This last result is very e ncouraging and could open the way to hydrological applications.