A multilayer simulation method for distributed polarimetric radar sounder architectures

Radar sounders (RS) are nadir-looking active instruments capable of non-invasively probing the subsurface of planetary bodies using electromagnetic waves. The SaTellite RAdar sounder for earTh sUbsurface Sensing (STRATUS) is a proposed satellite mission for Earth Observation aimed at investigating the Earth's subsurface in polar and arid regions. This mission proposes the novel concept of spaceborne Distributed Radar Sounder (DRS) architecture with a mothership transmitter-receiver satellite and multiple auxiliary receivers satellites. The DRS architecture mitigates the limitations of traditional dipole-based RS by using a distributed sensor array for reducing surface clutter using beamforming techniques, enhancing signal-to-noise ratio by optimizing multi sensor arrangement, and enabling interferometric processing for improved subsurface investigations. Since the DRS concept has only been theorized, simulations are essential to evaluate its performance. Currently, no simulation techniques efficiently address DRS architectures combined with multiple polarization acquisitions. In this work, we propose a DRS multilayer and multi-polarization simulation methodology for supporting STRATUS like RS architectures. The proposed technique extends the capabilities of the state-of-the-art multilayer coherent radargram simulator (MCRS), adapting it into a multilayer, multi-platform coherent radargram simulator with polarimetric functionality. This extension is very relevant also for making it possible to simulate complex acquisition scenarios in currently operating planetary missions. Our experimental tests focus on evaluating the behavior of the DRS architecture simulator and the related integration of polarization and assessing comparisons with monostatic architectures and post-processing analysis of Direction of Arrival (DOA) retrieval. These results assess the effectiveness of the DRS simulator in terms of the acquisition procedure.