Anomaly distinguishability in an asteroid analogue using quasi-monostatic experimental radar measurements

TL;DR

This work tackles the problem of distinguishing interior anomalies in asteroid-like targets using quasi-monostatic radar measurements on laboratory analogues. It blends time-frequency representations (spectrogram and wavelet), PCA-based filtering, and filtered backpropagation to produce rapid topographic and tomographic reconstructions, comparing a detailed interior model with a homogeneous one. The results demonstrate that wavefield information and appropriate filtering improve reconstruction quality, and attenuation correction further reduces artefacts, enabling interior-feature distinguishability at practical SNRs. The framework has direct relevance for interpreting planetary radar data from missions like Hera/Juventas Juventas and offers a path toward robust interior characterization of small bodies from limited laboratory-like measurements.

Abstract

This study conducts a quantitative distinguishability analysis using quasi-monostatic experimental radar data to find a topographic and backpropagated tomographic reconstruction for an analogue of asteroid Itokawa (25143). In particular, we consider a combination of travel-time and wavefield backpropagation tomography using the time-frequency representation (TFR) and principal component analysis (PCA) approaches as filtering techniques. Furthermore, we hypothesise that the travel time of the main peaks in the signal can be projected as a topographic imaging of the analogue asteroid while also presenting a tomographic reconstruction based on the main peaks in the signal. We compare the performance of several different filtering approaches covering several noise levels and two hypothetical interior structures: homogeneous and detailed. Our results suggest that wavefield information is vital for obtaining an appropriate reconstruction quality regardless of the noise level and that different filters affect the distinguishability under different assumptions of the noise. The results also suggest that the main peaks of the measured signal can be used to topographically distinguish the signatures in the measurements, hence the interior structure of the different analogue asteroids. Similarly, a tomographic reconstruction with the main peaks of the measured signal can be used to distinguish the interior structure of the different analogue asteroids.

Figures (13)

• Figure 1: 3D printed Analogue of the asteroid Itokawa. Left: Detailed model (DM) showing the surface layer, interior, and the deep interior void. Right: Homogeneous model (HM) showing a uniform distribution with no compartments.
• Figure 2: The quasi-monostatic signal configuration of 2732 measurement positions with a 12-degree elevation angle separation between the transmitter and receiver.
• Figure 3: Schematic representation of a first-order scattering from the target to the receiver in thick lines versus the higher-order scattering in the dashed lines.
• Figure 4: Time-frequency maps for the 1st--3rd principal component obtained using spectrogram and wavelet approach. The spectrogram and wavelet TFRs have bandwidths of $\approx 0.11$ and $\approx 0.1$ GHz, respectively. The datasets of the homogeneous and detailed object are considered in the 1st--2nd and 3rd--4th columns, respectively.
• Figure 5: Topographic projection of the maximum energy on the surface of a unit sphere and the difference on the analogue using the spectrogram and wavelet approach.