The seismic ordnance detection system (SODS) operates in a manner similar to an active sonar system. The system incorporates a mobile seismic array that sends broadband reducing vibrational energy into the ground. Once these waves encounter an object with anomalous mechanical properties, they cause the object to rotate, translate, and "ring," scattering energy back to the surface. These echoes then are received by an array of geophones and digitally recorded. The received signals are transformed to locate the objects and to analyze the characteristic echo of the object. These characteristic echoes, when used in conjunction with the magnetic and electrical responses, will efficiently differentiate unexploded ordnance (UXO) from inert objects. After the development and performance characterization of the SODS, the system can be utilized as one of a suite of sensors that can be tailored to specific site conditions and UXO types.
This project seeks to investigate and develop a new SODS which can improve the discrimination of UXO from clutter and thus reduce the number of excavations required during UXO remediation.
The technical approach for the investigation and development of the SODS consists of three phases including: (1) the performance of an initial feasibility study to analyze the practicality of seismic UXO detection using short wavelength shear waves; (2) the development of a proof-of-concept SODS for testing; and (3) the evaluation of the proof-of-concept SODS under controlled testing. The system simulation of SODS will be based on computer modeling and field measurements of seismic wave propagation and noise. The second phase will utilize seismic sources and receivers that provide greater bandwidth, increased source level, and better earth coupling than are commercially available while engineering a practical mobile array of seismic transducers that can be used to collect seismic data efficiently. The third phase will involve refining the proof-of-concept system through diagnostic tests and analyzing the detections of UXO. This will culminate in an initial evaluation of the SODS in multi-sensor tests and an analysis of false alarm reduction rates using the seismic data in a sensor fusion process.
During FY 1999, a proof-of-concept was engineered and tested. A 60-element receiver array and a high-frequency vibrator seismic source were integrated with a 72-channel data acquisition system. Initial tests detected a seismic response from a 55 mm shell. Analysis is under way to improve system performance.
The project intends to provide SERDP with a fully developed SODS that will (1) significantly improve the accuracy of UXO site characterization, thereby reducing excavations and cleanup costs; (2) provide UXO detection and classification capabilities in environments where other sensors perform poorly; and (3) detect nonmetallic ordnance and other buried wastes or structures.