Wireless, acoustically linked, undersea, magnetometer sensor network

This paper presents a magnetometer sensor node design that consists of a He3 nuclear precession total-field magnetometer, data acquisition and recording electronics, and acoustic modem for networking such nodes. Expounding, we describe the integration of an ultra-sensitive magnetometer with the support electronics just mentioned. Additionally, the fully integrated, stand-alone magnetometer sensor node's self-noise performance is presented and compared with reference magnetometers. Due to the induced noise of the earth's background field, magnetometer data from multiple sensors is required in order to maximize the system detection range, thereby minimizing the overall number of required nodes to cover a given area. Given the aversion to continuously streaming data via the acoustic communications network between pairs of sensors, an alternative method is presented to minimize this traffic while still detecting objects of interest in the presence of the earth's field, with the cost being decreased detection ranges. Preliminary filtering techniques and an autoregressive process for implementing a noise whitening filter in addition to the application of orthonormal basis functions based on Anderson functions increase the single sensor detection range in the 0.001 to 0.030 Hz band representative of a passing vessel relative to the stationary sesnor. The filter's noise suppression performance conducted onboard a single sensor and application to collected data is presented.