398 
favorably (increase in magnitude) to the decrease of ks. After this date the slope A increases; we think that this 
is due to the developing vegetation (see fig.l) which maskes the soil. 
8. CONCLUSION 
In this paper we reached the conclusion that ERS1 WSC can be used to assess vegetation. Before the vegetation 
cover is too important, we have a good qualitative relationship between measured soil moisture and a 0 in 18-21° 
range. As it is difficult to have soil measurements over 50*50Km area, we take advantage of WSC spatial 
resolution to extract soil roughness and soil moisture through empirical model. Validation of our inversion 
method will rely on “mesoscale” modeling results. 
Theoretical studies have shown that, to assess soil moisture, vegetation effects on signal may be taken into 
account. 
Our futures steps will consider: 
-Vegetation cover study in term of soil moisture estimation. 
-Validation of surface roughness concept at large scale. 
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ACKNOWLEDGEMENTS 
The authors are indebted to D. Vidal madjar for the discussion which initiated this study, to ESA, IFREMER 
and L. Cunin AGRYMET for providing us with excellent satelite data, to A. Chanzy, A. Chehbouni, L. 
Laguerre, T. Lebel, and B. Monteny for the ground work during the HAPEX Experiment, and to finally to T. 
Valero and S. Wagner for the intensive satellite data preprocessing.