The European Space Agency (ESA) is conducting Phase A studies of a 435 MHz low-earth orbiting polarimetric synthetic aperture radar (SAR) called BIOMASS. If selected as the next ESA Earth Explorer mission, BIOMASS will provide unique global measurements of forest biomass and height. This paper describes the simulation of ionospheric effects on BIOMASS and their mitigation as implemented within an end-to-end simulator (E2ES) of BIOMASS radar products.
The E2ES incorporates an ionosphere generation module (IGM) and an ionospheric correction module. The IGM supplies a Faraday rotation (FR) map which is used to synthesise SAR images based on the radar geometry, a model value of total electron content and the International Geomagnetic Reference Field. Scintillation is simulated by partially decompressing a single-look complex image in azimuth (to reconstruct the raw complex data sequence at ionospheric height), multiplying by a thin two-dimensional random phase screen generated from a database of spatial phase spectrum parameters (derived from the WBMOD model) and then recompressing in azimuth. The ionospheric correction module, provides interfaces to a range of FR correction algorithms and azimuth displacement correction for multiple-acquisition images used for interferometry.
A statistical analysis of where scintillation effects are likely to be significant under the dawn-dusk orbit proposed for BIOMASS suggests that, taking a PSLR of 5 dB as a minimum requirement, autofocusing of BIOMASS images should be feasible or not required for the vast majority of forest regions (below 70° geomagnetic latitude) subject to clutter and noise.