The launch of ENVISAT in 2002 and the operation of the ASAR instrument has immediately questioned some important assumptions concerning the nature and stability of radar measurements of soils and vegetation. The key observations concerned large localized discrepancies (“flashing”) between measurements made by the ENVISAT ASAR instrument and the ERS-2 AMI, within 30 minutes of each other over Flevoland in the Netherlands. The discrepancies appeared not to be related to changing environmental conditions but rather to the fine differences in the observation geometries of the two instruments. Such sensitivity was not predicted by the models for microwave interaction usually applied to soils and vegetation. The presence of poorly characterized anomalies of this type may have severe implications for the confidence with which we assimilate satellite SAR data in land surface process models. Consequently, it was needed to improve the understanding of the phenomenon and examine strategies for mitigating its effects.
The overall objective of our study was to improve the understanding of directional scattering, for which two main issues had to be addressed:
1. consolidate the experimental evidence of directional scattering and support its understanding by a dedicated ground campaign
2. develop an improved theoretical model in order to better quantify and assess the relevance of the directional scattering with very narrow scattering pattern.
TYPE AND DATE
STARTING DATE – 2008
ENDING DATE – 2010
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GAMMA REMOTE SENSING Switzerland, (Coordinator)
UNIVERSITY OF MUNICH , Germany