Sparse source travel-time tomography of a laboratory target: accuracy and robustness of anomaly detection

TL;DR

This paper investigates the minimum number of sources needed for accurate anomaly detection in sparse source travel-time tomography, demonstrating that three or four sources provide reliable results in a laboratory setting.

Contribution

It introduces a statistical inversion approach to determine the optimal number and placement of sources for robust anomaly detection in sparse tomography.

Findings

Three or four sources yield reliable anomaly detection.

Source configurations can be ranked by performance.

Results applicable to planetary missions and material testing.

Abstract

This study concerned conebeam travel-time tomography. The focus was on a sparse distribution of signal sources that can be necessary in a challenging in situ environment such as in asteroid tomography. The goal was to approximate the minimum number of source positions needed for robust detection of refractive anomalies, e.g., voids within an asteroid or a casting defects in concrete. Experimental ultrasonic data were recorded utilizing as a target a 150 mm plastic cast cube containing three stones with diameter between 22 and 41 mm. A signal frequency of 55 kHz (35 mm wavelength) was used. Source counts from one to six were tested for different placements. Based on our statistical inversion approach and analysis of the results, three or four sources were found to lead to reliable inversion. The source configurations investigated were also ranked according to their performance. Our results can be used, for example, in the planning of planetary missions as well as in material testing.