An Approach to the Simulation of Radar Sounder Radargrams Based on Geological Analogs

Simulation of radar sounder (RS) data is important for understanding the radar response of subsurface features to facilitate the interpretation of the real data. Conventional electromagnetic simulators require the definition of complex geoelectrical models of the investigated targets. They also involve time-complex solutions of Maxwell's equations for computing the received electric field, which leads to very high computation time. Furthermore, the simulated radargrams are often not realistic as it is very difficult to model all the variables involved in the data acquisition. In this paper, we propose a novel simulation approach that exploits the data available from existing RSs in geologically analogous terrains, to produce realistic simulations of the investigated RS target. This simulation strategy is based on minimizing the difference between the analog and the investigated acquisition scenarios. This is done by applying a series of corrections, which depend on the relation between the radargram characteristics and the physical variables describing the acquisition process. The aim is to produce radargrams that resemble the investigated scenario in terms of the echo magnitude, bandwidth, range resolution, and along-track resolution. Experimental results present three case studies for different possibilities of the analog and the investigated scenarios. The validation of the simulated radargrams with actual data demonstrates the effectiveness of the proposed approach. Finally, we also present a real application of this approach for the simulation of Radar for Icy Moon Exploration (RIME) radargrams for a combination of instrument and target parameters, using the SHAllow RADar (SHARAD) radargram acquired over the geological analog of a selected RIME target.

I. Introduction

Radar sounders (RS) are low-frequency instruments for profiling the subsurface of the Earth or of other planetary bodies. By measuring the echo returns from interfaces of significant dielectric contrast, RS produces radargrams indicating compositional and structural discontinuities that can help to understand and characterize planetary shallow subsurfaces. At present, there are RS orbiting around Mars (i.e., SHAllow RADar (SHARAD) [1] and Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) [2]), the Moon (i.e., Lunar Radar Sounder (LRS) [3]) and a number of airborne RS missions over the polar ice caps of the Earth. Furthermore, two Jovian missions that will carry RS are under development. These are the Radar for Icy Moon Exploration (RIME) [4], which is aimed at studying the icy moons Ganymede, Callisto and Europa, and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) [5], which is specifically targeted at Europa.