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The TanDEM-X mission [1] provides for the first time single pass (single- and dual-) polarimetric interferometric data from space. This allows the acquisition and analysis of Pol-InSAR data without the disturbing effect of temporal decorrelation on a global scale. Polarimetric interferometric X-band data are now available for different forest ecosystems (from boreal to tropics) in different seasons. The penetration capability of X-band in vegetation is limited and depends strongly on the corresponding forest conditions. However, first data analysis showed sufficient penetration to apply Pol-InSAR height estimation at least for a boreal forest scenario [2]. The limitations of X-band for forest parameter estimation can be identified by analyzing data sets from different forest types. Additionally seasonal effects like leaf fall or freezing conditions may change the backscattering behavior or penetration capability of X-band for forests. It was already shown that the ability to penetration depends on the seasonal stage of a forest. Figure 1 on the left shows the penetration depth of X-band by means of boreal forest (Krycklan forest northern Sweden) for a summer (Figure 1 left side) and a winter (Figure 1 middle) acquisition. Penetration depth of the winter acquisition is with a mean of 11.8m significantly larger than for the summer acquisition with a mean of 9.45m. This is probably due the lower dielectricity of the tree compartments in frozen conditions.

Ill., graph. Darst.