Abstract: A method is disclosed comprising: transmitting a pair of tracking signals, the pair of tracking signals including a first tracking signal and a second tracking signal; receiving a data set that is collected by using a sensor in a sensor array, the data set including: (i) a received first tracking signal that is generated by the sensor in response to receiving the first tracking signal, (ii) a received second tracking signal that is generated by the sensor in response to receiving the second tracking signal, and (iii) a received target signal; detecting a relative delay at which the first tracking signal and the second tracking signal are received by the sensor; removing the received first tracking signal and the received second tracking signal from the data set to produce a filtered data set; and providing the filtered data set and an indication of the relative delay to a beamformer.

Abstract: Methods and apparatus for inspecting an underwater vehicle. In embodiments, a system receives a SAR image for at least a portion of an exterior surface of an underwater vehicle and performs CCD processing to compare a baseline SAS image for the underwater vehicle with the received SAR image of the underwater vehicle to generate a CCD output corresponding to a measure of similarity of the baseline SAS image and the received SAS image. The system determines whether there was tampering of the underwater vehicle based on the measure of similarity.

Abstract: An underwater celestial navigation beacon configured to provide position information is disclosed. The underwater celestial navigation beacon can include a data store configured to store an astronomical model of the moon. The underwater celestial navigation beacon can include an inertial measurement unit (IMU) operable to capture IMU data that includes three-axis acceleration data and three-axis rate gyroscopic data. The underwater celestial navigation beacon can include a controller. The controller can determine a latitude of the underwater celestial navigation beacon using the three-axis rate gyroscopic data. The controller can determine a longitude of the underwater celestial navigation beacon based on a gravitational pull of the moon, using the three-axis acceleration data and the astronomical model of the moon. The controller can determine the position information for the underwater celestial navigation beacon based on the latitude and longitude.

Abstract: A sensor system includes a triplet element including a first hydrophone, a second hydrophone, and a third hydrophone configured to receive an incoming signal at a first phase, a second phase, and a third phase, respectively, the first to third hydrophones extending along a first direction, and a processor configured to determine an incidence direction of the incoming signal, and to dynamically generate a cardioid null in the incidence direction to reject the incoming signal based on the incoming signal at the first to third phases.

Abstract: Methods and apparatus for inspecting an underwater vehicle. In embodiments, a system receives a SAR image for at least a portion of an exterior surface of an underwater vehicle and performs CCD processing to compare a baseline SAS image for the underwater vehicle with the received SAR image of the underwater vehicle to generate a CCD output corresponding to a measure of similarity of the baseline SAS image and the received SAS image. The system determines whether there was tampering of the underwater vehicle based on the measure of similarity.

Abstract: A sensor system includes a triplet element including a first hydrophone, a second hydrophone, and a third hydrophone configured to receive an incoming signal at a first phase, a second phase, and a third phase, respectively, the first to third hydrophones extending along a first direction, and a processor configured to determine an incidence direction of the incoming signal, and to dynamically generate a cardioid null in the incidence direction to reject the incoming signal based on the incoming signal at the first to third phases.

Abstract: An underwater celestial navigation beacon configured to provide position information is disclosed. The underwater celestial navigation beacon can include a data store configured to store an astronomical model of the moon. The underwater celestial navigation beacon can include an inertial measurement unit (IMU) operable to capture IMU data that includes three-axis acceleration data and three-axis rate gyroscopic data. The underwater celestial navigation beacon can include a controller. The controller can determine a latitude of the underwater celestial navigation beacon using the three-axis rate gyroscopic data. The controller can determine a longitude of the underwater celestial navigation beacon based on a gravitational pull of the moon, using the three-axis acceleration data and the astronomical model of the moon. The controller can determine the position information for the underwater celestial navigation beacon based on the latitude and longitude.

Abstract: A method is disclosed comprising: transmitting a pair of tracking signals, the pair of tracking signals including a first tracking signal and a second tracking signal; receiving a data set that is collected by using a sensor in a sensor array, the data set including: (i) a received first tracking signal that is generated by the sensor in response to receiving the first tracking signal, (ii) a received second tracking signal that is generated by the sensor in response to receiving the second tracking signal, and (iii) a received target signal; detecting a relative delay at which the first tracking signal and the second tracking signal are received by the sensor; removing the received first tracking signal and the received second tracking signal from the data set to produce a filtered data set; and providing the filtered data set and an indication of the relative delay to a beamformer.

Abstract: A method and system for facilitating navigation of an autonomous underwater vehicle (AUV) about an egress path that mirrors an ingress path. Complex return data during an ingress cycle are obtained and a corresponding complex image of the seabed along the ingress cycle is generated. Complex return data during an egress cycle are also obtained and a plurality of corresponding complex local images of the seabed along the egress cycle can be generated. The complex local images are compared to the complex ingress image to identify a normalized cross-correlation coefficient (NCCC). A maximum NCCC indicates that a position of the AUV in the along-track direction has been found. Successive local complex images from the egress cycle can be compared against the complex image from the ingress cycle as the AUV moves along the egress path to identify successive NCCCs, and monitored overtime to determine if the successive NCCCs are increasing or decreasing as the AUV moves along the egress path.

Abstract: A method and system for facilitating navigation of an autonomous underwater vehicle (AUV) about an egress path that mirrors an ingress path. Complex return data during an ingress cycle are obtained and a corresponding complex image of the seabed along the ingress cycle is generated. Complex return data during an egress cycle are also obtained and a plurality of corresponding complex local images of the seabed along the egress cycle can be generated. The complex local images are compared to the complex ingress image to identify a normalized cross-correlation coefficient (NCCC). A maximum NCCC indicates that a position of the AUV in the along-track direction has been found. Successive local complex images from the egress cycle can be compared against the complex image from the ingress cycle as the AUV moves along the egress path to identify successive NCCCs, and monitored overtime to determine if the successive NCCCs are increasing or decreasing as the AUV moves along the egress path.

Abstract: A compensation filter is operable to receive a received signal in response to a transmitted signal, the received signal having a time duration. The compensation filter is operable to generate a compensated signal. The compensation filter changes shape of an associated transfer function during the time duration of the received signal to result in the compensated signal having an improved spectral flatness throughout the time duration of the received signal. The compensation filter can be used in a sonar system. A method, which can be used in a sonar system, uses the compensation filter.

Abstract: A method uses an underwater vehicle travelling along an underwater surface projecting high frequency sound at the underwater surface to produce an image of the underwater surface with sufficient along track and cross track resolution to be able to identify cracks or other irregularities in the underwater surface.

Abstract: A system for adjusting phase centers of a receiving array in real time. In one embodiment, a transmitter transmits a sequence of pings. Receiving elements are grouped into staves and summed prior to subsequent processing, and the groups are selected so that the phase center on a ping is substantially in the same location as another phase center on a previous ping.

Abstract: A method uses an underwater vehicle travelling along an underwater surface projecting high frequency sound at the underwater surface to produce an image of the underwater surface with sufficient along track and cross track resolution to be able to identify cracks or other irregularities in the underwater surface.

Abstract: A compensation filter is operable to receive a received signal in response to a transmitted signal, the received signal having a time duration. The compensation filter is operable to generate a compensated signal. The compensation filter changes shape of an associated transfer function during the time duration of the received signal to result in the compensated signal having an improved spectral flatness throughout the time duration of the received signal. The compensation filter can be used in a sonar system. A method, which can be used in a sonar system, uses the compensation filter.

Abstract: A system for adjusting phase centers of a receiving array in real time. In one embodiment, a transmitter transmits a sequence of pings. Receiving elements are grouped into staves and summed prior to subsequent processing, and the groups are selected so that the phase center on a ping is substantially in the same location as another phase center on a previous ping.