Abstract: In various embodiments, a passive bearing detector is disclosed. The passive bearing detector comprises a plurality of hydrophones. The plurality of hydrophones is arranged in a three-dimensional geometry. The three-dimensional geometry exposes each of the plurality of hydrophones to an ambient aquatic acoustic environment. The passive bearing detector further comprises a processor electrically coupled to the plurality of hydrophones. The processor is configured to determine a direction of arrival of an unknown broadband acoustic signal received by the plurality of hydrophones based on the phase difference of the unknown broadband acoustic signal at each of the plurality of hydrophones.

Abstract: Methods and apparatus determining a position of a submersible vehicle within a body of water are provided. A method comprises determining an initial position of the vehicle while the vehicle is at or near a water surface. The method further comprises coupling the vehicle and a base node to a weight and determining a position of the base node once the base node and vehicle have reached the floor of the body of water using acoustic modems of the vehicle and a surface vessel to aid in calculating the position as they descend, and acoustically transferring the at rest position on the seafloor from the vehicle to the node. The method further comprises decoupling the vehicle from the node and weight and determining a position of the vehicle based on the position of the base node and acoustic signals exchanged between acoustic modems of the vehicle and the base node.

Abstract: Methods and apparatus determining a position of a submersible vehicle within a body of water are provided. A method comprises determining an initial position of the vehicle while the vehicle is at or near a water surface. The method further comprises coupling the vehicle and a base node to a weight and determining a position of the base node once the base node and vehicle have reached the floor of the body of water using acoustic modems of the vehicle and a surface vessel to aid in calculating the position as they descend, and acoustically transferring the at rest position on the seafloor from the vehicle to the node. The method further comprises decoupling the vehicle from the node and weight and determining a position of the vehicle based on the position of the base node and acoustic signals exchanged between acoustic modems of the vehicle and the base node.

Abstract: Methods and apparatus determining a position of a submersible vehicle within a body of water are provided. A method comprises determining an initial position of the vehicle while the vehicle is at or near a water surface. The method further comprises coupling the vehicle and a base node to a weight and determining a position of the base node once the base node and vehicle have reached the floor of the body of water using acoustic modems of the vehicle and a surface vessel to aid in calculating the position as they descend, and acoustically transferring the at rest position on the seafloor from the vehicle to the node. The method further comprises decoupling the vehicle from the node and weight and determining a position of the vehicle based on the position of the base node and acoustic signals exchanged between acoustic modems of the vehicle and the base node.

Abstract: In various embodiments, a passive bearing detector is disclosed. The passive bearing detector comprises a plurality of hydrophones. The plurality of hydrophones is arranged in a three-dimensional geometry. The three-dimensional geometry exposes each of the plurality of hydrophones to an ambient aquatic acoustic environment. The passive bearing detector further comprises a processor electrically coupled to the plurality of hydrophones. The processor is configured to determine a direction of arrival of an unknown broadband acoustic signal received by the plurality of hydrophones based on the phase difference of the unknown broadband acoustic signal at each of the plurality of hydrophones.

Abstract: Methods and apparatus determining a position of a submersible vehicle within a body of water are provided. A method comprises determining an initial position of the vehicle while the vehicle is at or near a water surface. The method further comprises coupling the vehicle and a base node to a weight and determining a position of the base node once the base node and vehicle have reached the floor of the body of water using acoustic modems of the vehicle and a surface vessel to aid in calculating the position as they descend, and acoustically transferring the at rest position on the seafloor from the vehicle to the node. The method further comprises decoupling the vehicle from the node and weight and determining a position of the vehicle based on the position of the base node and acoustic signals exchanged between acoustic modems of the vehicle and the base node.

Abstract: A method and apparatus for determining the geophysical position of an autonomous underwater system utilizing underwater acoustic modems that exchange broadband underwater acoustic signals. The method of the invention includes the steps of initiating an exchange of broadband acoustic signals between the autonomous system of unknown geophysical position and a base system of known geophysical position wherein the depths of both systems is known. A bearing calculation is made on one of the signals transmitted between the systems, preferably through the use of an array of hydrophones placed closely together at predetermined locations on either the autonomous or base system. Also, the range between the two systems is determined by measuring the time of travel of at least one signal.

Abstract: An underwater communications method and apparatus is provided for demodulating communications signals while compensating for the effects of range rate, i.e., relative velocity between the nodes of the communication system. The method of the invention is implemented in the DSP of an underwater bi-directional acoustic modem and method comprises the steps of generating a communication signal with an acquisition component for providing an initial estimate of the range rate. The acquisition component preferably is with a nonlinear frequency modulated acquisition component, preferably in the form of a hyperbolic frequency modulated signal, for providing the initial estimate of the range rate. Following this, a second set of signals, preferably a set of single frequency tonals, is generated and acquired using the initial estimate of range rate to obtain a more precise estimate of range rate.

Abstract: A data communications and underwater release management system for acquiring data from remote positively buoyant instrumentation packages moored underwater through the use of an intervening mechanical release coupled at one end to the buoyant instrumentation package and at the other to the mooring. A topside modem system provides bidirectional communication with an undersea modem commonly housed with the release to permit data generated from the instrumentation to be conveyed topside and/or send command signals to release the instrumentation package so that it can ascend to the surface for recovery, repair, or refitting. Power is supplied via an on-board battery whose energy level is monitored and directed when below a threshold value to operate only the mechanical release.