Artefact Analysis of Multistatic Three-Dimensional SAR Imaging with Two Linear Trajectories

TL;DR

The paper develops a microlocal analysis of a 3D multistatic SAR system where transmitters and receivers move along two straight lines at a fixed altitude and with angle $\beta$ between the lines. Modeling the data by a forward operator $F$ that is a Fourier Integral Operator with phase $\Phi$ and reflectivity $V$, the authors study the normal operator $F^{*}F$ via the canonical relation $C$ and its composition, establishing a time-gating condition to suppress artefacts in the ROI. For both perpendicular and non-perpendicular line configurations, they show that, with suitable geometry and a sufficiently large propagation-parameter $\rho$, the only artefacts left are transceiver-plane mirror images, with prior walkaway artefacts avoided by the proposed time-domain constraints. Numerical simulations across multiple $\beta$ values corroborate the theoretical findings, demonstrating artefact suppression and validating the time-gating strategy and the two-line aperture approach for 3D SAR imaging in realistic configurations.

Abstract

In recent years, radar technology has seen much improvement, making multistatic Synthetic Aperture Radar (SAR) sensing a realistic possibility, for example in satellite constellations or unmanned aircraft systems. With such systems, there then comes the requirement to investigate useful multistatic SAR geometries. We provide a microlocal analysis of a multistatic data acquisition geometry for three-dimensional SAR imaging, where the transmitter and receiver move independently along two straight lines covering a region of interest (ROI). Using microlocal techniques, we show how the data acquisition geometry influences whether artefacts are likely to be present in the resultant image and how they can be avoided. Our main contribution is to provide a time-gating condition on the data which ensures that artefacts are not present in the ROI. As an independent verification, we provide several numerical simulations which follow a time-independent formulation.

Figures (5)

• Figure 1: Illustration of the proposed acquisition geometry, showing generic positions of the transmitter $\gamma_1(s)$, receiver $\gamma_2(r)$ and a scatterer at $x$ with coordinates $(x_1,x_2,x_3)$.
• Figure 2: Canonical projections
• Figure 3: Different views of the simulation scene for the radar geometry with transmitter to receiver axis angle $\beta=90^{\circ}$. The blue stars represent point scatterers, the black circle represents the scene centre. The blue and red lines represent the transmitter and receiver positions. The magenta surface constitutes the virtual BEM transceiver SAR aperture.
• Figure 4: Three-dimensional SAR image $z$-direction MIPs (top view) with SAR aperture overlaid, for radar geometries with transmitter to receiver axis angles $\beta$ of (a) $30^{\circ}$ (b) $60^{\circ}$ (c) $90^{\circ}$ and (d) $120^{\circ}$. The colour-bar (e) represents normalized scattering intensity and pertains to all images.
• Figure 5: Three-dimensional SAR image y-direction MIPs (side view) with SAR aperture overlaid, for radar geometries with transmitter to receiver axis angles $\beta$ of (a) $30^{\circ}$ (b) $60^{\circ}$ (c) $90^{\circ}$ and (d) $120^{\circ}$. The colour-bar (e) represents normalized scattering intensity and pertains to all images.