Bandwidth Effects in Pol-InSAR Forest Height Estimation Performance at P-band

Abstract

Polarimetric SAR interferometry (Pol-InSAR) is a new radar technology that allows us to investigate vegetation structure properties such as forest height and biomass. The coherent combination of radar polarimetry and SAR interferometry provides the sensitivity to the vertical distribution of scattering process within the resolution cell and can be used for model-based inversion of forest structure parameters. Indeed, model based (using the Random Volume over Ground (RVoG) model) forest height estimation has been successfully demonstrated using airborne repeat pass fully polarimetric interferometry at a wide range of frequencies. The estimation of forest height (and its close relation to forest biomass) becomes important in the frame of BIOMASS mission, a P-band SAR mission currently under review as a candidate mission in the ESA Earth Explorer Opportunity Programme series. The main objective of the BIOMASS mission is to provide consistent global estimates of forest biomass, forest disturbance and re-growth. However, the ITU allocation limit dramatically the system bandwidth at P-band to 6MHz at 432-438MHz. In this work we assess the impact of bandwidth on the Pol-InSAR inversion performance and evaluate the expected performance. We analyze the possible performance and the associated system requirements for forest parameter estimation techniques in the frame of the BIOMASS system and mission operation scenario. The performance analyses is supported and validated by E-SAR Pol-InSAR experimental data and some allometric data acquired in the frame of the BioSAR campaign. In order to support the future BIOMASS mission, the ESA airborne radar campaign carried out over the boreal forests of southern Sweden. The E-SAR (Experimental Synthetic Aperture Radar) airborne data were collected over a period of two months (09/03/2007 – 02/05/2007) to simulate the impact of bandwidth and the time-gap between successive acquisitions from BIOMASS sensor. The impact of reduced bandwidth is investigated using the filtered 6 MHz P-band data. A comparison of the inversion results between 70 MHz and 6 MHz bandwidth in P-band data is performed and discussed.