Pol-InSAR Forest Height Estimation in the Context of BIOMASS
Papathanassiou, Kostas1; Lee, Seung-Kuk2; Kugler, Florian2; Scheiber, Rolf2; Lopez Dekker, Francisco2
1DLR, GERMANY; 2Microwaves and Radar Institute, DLR, GERMANY
BIOMASS is ESA's Earth Explorer 7 mission proposal with primary objective to perform global measurements of forest biomass for assessing terrestrial carbon stocks and fluxes. Secondary mission objectives are the estimation of ice-sheet thickness and internal structures in cold regions as well as subsurface geology in arid regions [ref],[ref]. The mission concept is envisaged as a spaceborne P-band synthetic aperture operating at the center frequency of 435 GHz and with a bandwidth of 6 MHz (i.e. the frequency range 432-438MHz which corresponds to the ITU allocation established at the World Radio-Communications Conference 2003). The baseline is a quad-pol operation mode that will allow fully-polarimetric repeat-pass interferometric acquisitions with a revisit time of 16 down to 3-4 days depending on the orbit implementation and mission operation.
One important component in the BIOMASS mission concept is the use of polarimetric interferometric (Pol-InSAR) techniques to estimate forest height. Forest height maps are by themself a BIOMASS product; but, even more important is to exploit the alometric relation between forest height and biomass to derive a biomass estimate that will support the intensity based biomass estimators. In this paper we evaluate the performance of forest height estimation at P-band based on a number of airborne campaigns and attempt to project the performance achieved into a spaceborne BIOMASS context. The Pol-InSAR model and single- / dual- and multi-baseline inversion approaches are introduced. The inversion is performed on a variety of sites representing all major forest ecosystems and the obtained inversion results are validated against airborne lidar reference data and discussed. Finally the achieved forest height estimation performance is extrapolated in the spaceborne BIOMASS case For this first airborne data are used to simulate BIOMASS Pol-InSAR data and then used to assess the performance of the developed single- and dual-baseline inversion approaches. Finally, elements of an End-2-End mission performance analysis are presented and discussed.