Sensitivity of TerraSAR-X, RADARSAT-2 and ALOS satellite radar data to crop variables

The aim of this work is to investigate the sensitivity of multi-incidence, multi-frequency and multi-polarized radar signatures over different crops (wheat, rapeseed, soybean, corn and sunflower). Time series of SAR images are acquired by TerraSAR-X (HH), RADARSAT-2 (full polarization) and ALOS (HH) over an agricultural site located in South West of France during the MCM´10 experiment synchronously with ground measurements. The angular normalization of radar signals is performed per crop type at X- and C-bands. The angular sensitivity of the backscatters decreases with the increase of the vegetation index (from 0.4 dB.°^-1 over bare soils to 0.05 dB.°^-1 for fully vegetated fields). Analyses of the radar time series show that X-, C- and L-bands behaviors are strongly contrasted, depending on the phenological stages of crops, highlighting the interest of using multi-frequency data. Crop height retrieval based on microwave data indicates promising results, with R² ranging from 0.7 to 0.93.