Initial Buried Minehunting Demonstration of the Laser Scalar Gradiometer Operating Onboard REMUS 600

The Laser Scalar Gradiometer (LSG) is a sensitive passive magnetic sensor based on the opto-magnetic properties of helium-4 gas in accordance with the Zeeman effect. The LSG has attained increased sensitivity over comparable sensors by the use of a laser in place of incoherent light for optical pumping. It employs four helium sense cells configured in a volume-filling arrangement to measure four independent channels of information: the scalar field magnitude and three linearly independent admixtures of the three components of the scalar-field gradient vector. The LSG has now been integrated into the REMUS 600 and evaluated in land-based testing. This land-based testing has assured the proper functionality of this integrated system prototype and established the sensor's noise floor in the electromagnetic environment of the REMUS 600. Following this land-based testing, at-sea shakedown tests and experiments over target fields have been conducted to provide a more definitive measure of the LSG's performance under actual operational conditions and to evaluate its current capability to detect, classify, and localize (DCL) buried mines. The system configuration, the experiment design, associated test procedures, and results of data analysis from the underwater experiments conducted with the LSG onboard REMUS 600 are reported in this paper.