Airborne and satellite SAR tomography: a tool to investigate forests and glaciers structures

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SYNERGIE [Axe_IRSTEA]TETIS-ATTOS

International audience

إنجليزي. Microwave radiations below say 1250MHz penetrate forests, dry ice and rocks. The use of airborne or satellite borne microwave sensors to image the subsurface with significant penetration is thus of high interest to analyse wide areas or even to make global surveys. Due to the large distance from the targets, the antenna has to be synthesized using a progressive scan and illuminating the targets from different positions. The radar returns are then properly combined using a computer. The position of the sensor has to be known to a fraction of a wavelength. This is rather easy to obtain if the sensor flies along a well-characterized track (synthetic aperture radar (Bamler and Hartl, 1998)). The creation of the across track aperture is much more difficult. It can be done by using many flights or orbits, which positions, however, need to be extremely well known. We show that this can be obtained by exploiting the characteristics of the targets. We will present the results obtained with airborne campaigns using polarimetric radars on boreal and tropical forests, which were carried out in order to estimate the above ground biomass. Campaigns have also been carried out over glaciers, to estimate the structure of the subsurface. We will then introduce two new satellites, Biomass and SAOCOM companion, planned to be deployed by the European Space Agency in the forthcoming years. Exploiting the results of the ad hoc airborne campaigns, the results to be obtained with these systems are simulated and presented.