USA As Represented by Secretary of the Navy

John J Holmes

John F Scarzello

Edward C O'Keefe

Robert Andrew Wingo

Donald E Pugsley

William A Venezia

Bruce R Hood

Eric S Dykes

Milton H Lackey

Robert W Schuler

Shirley Steffey

Christopher I Conner

According to exemplary inventive practice, an ADCP system (including one or more acoustic Doppler current profilers) and a magnetometer system (including one or more magnetometers) are placed underwater. The ADCP system is used to obtain ADCP time series data. The magnetometer system is used to obtain magnetometer time series data. A computer performs computations with respect to input from the ADCP system and input from the magnetometer system. The computations include formulation of a least squares matrix to minimize a least squared error between the ADCP time series data and the magnetometer time series data. The present invention may be practiced, for instance, whereby a magnetometer is centrally located in relation to a triangular arrangement of three ADCPs, or whereby the ADCP system and the magnetometer system are co-located.

Underwater electromagnetic field measurement that factors in ocean dynamics

According to exemplary inventive practice, a deployment line connects a vessel to an anchor, and a tether connects a buoyant electronic unit to the same anchor. The buoyant electronic unit includes a syntactic foam sphere, and a computer and sensors that are housed in the sphere. The anchor and the buoyant electronic unit are discharged from the vessel and sink in the water. The deployment line mechanically detaches from the anchor when the anchor reaches bottom. The buoyant electronic unit stabilizes into an equilibrium position, tethered vertically and tautly to the anchor. Measurements pertaining to phenomena such as underwater electric potential, pressure, magnetic field, and acceleration are taken by the corresponding sensors and are processed by the computer. An electrical (e.g., acoustical) signal is transmitted to detach the tether from the anchor, whereupon the buoyant electronic unit rises to a retrievable position on the surface of the water.

Method and system for measuring physical phenomena in an open water environment

The present invention provides three different algorithms, namely, the 'divide and conquer' algorithm, the 'Hiddensee compensation' algorithm, and the &#x201c;impulse response&#x201d; algorithm. Any one of these three inventive algorithms may be made a part of an overall degaussing algorithm for a marine vessel. Each corrective algorithm, by itself, compensates for deviation of the vessel's induced signature from direct, linear proportionality to the ambient magnetic field. This deviation is associated with the dependency of a marine vessel's magnetic signature on the frequency at which the vessel rolls in the water. Practice of inventive compensation tends to be increasingly called for with increasing magnetic character of the vessel.

Roll frequency dependency correction to control magnetic ship signatures

Removal of extraneous magnetic measurement components from magnetic anomaly detection (MAD) tends to increase its accuracy. Conventional removal accounts for anomalous magnetism manifested by the MAD vehicle (typically, unmanned), but assumes that the magnetic field applied to the MAD vehicle is the earth's magnetic field, i.e., is non-anomalous and known. In contrast, the present invention accounts not only for anomalous magnetism manifested by the MAD vehicle, but also for anomalous magnetism manifested in the MAD vehicle's vicinity, such as by a manned control vehicle. The present invention's mathematical characterization of vehicular 'self-noise' due to induced and permanent magnetization is more refined, especially insofar as treating the vehicle's ambient magnetic field as an unknown (empirical) quantity, rather than a known (non-empirical) quantity. A typical inventive system for vehicular magnetic self-noise-reduced magnetic anomaly detection includes magnetic and other sensors, and a computer implementing the inventive mathematical characterization in processing the signals.

Algorithmic reduction of vehicular magnetic self-noise

A plurality of sensing modules are deployed by positioning thereof in spaced relation to each other on a seafloor surface at a shallow depth to establish a targeted seawater zone within which certain conditions are detected, such as those produced by the presence of a sea vessel such as a submarine within the targeted zone. Data signals are generated within the deployed sensing modules in response to said detection of the submarine for radio frequency transmission above the seawater targeted zone from floating transmitters ejected from the sensing modules positioned on the seafloor surface after detection of the submarine.

Underwater surveillance system

An elongated optical fiber is vertically positioned within seawater in a deep-depth targeted zone by vertical suspension thereof from a floating buoy. Electrode sensor arrays are positioned in vertically spaced relation to each other on the optical fiber for generating warning signals in response to detection of hostile conditions. The warning signals are converted into signal data collected and transferred to a transmitter in the floating buoy from which the sensor arrays are suspended within the targeted zone positioned on the optical fiber. Such collected data signals are transmitted through an antenna within the floating buoy to locations above the seawater surface for surveillance purposes.

Deep water surveillance system

The electromagnetic field produced by an electrical device is electromagnetically canceled by a three-dimensional configuration of electrical coils which together provide a box-like enclosure having at least six sides/faces. The electromagnetic containment of the electromagnetic field is effected via the physical occurrence of zero magnetic flux perpendicularly through each side/face. At least one coil is positioned in correspondence with each side/face of the box-like enclosure. Each coil has a set of conductors divided into two halves in terms of circuitry, the conductors in each half being connected to each other in series. With regard to each coil, a first amplifier receives an electrical signal from the first conductor half and outputs to a second amplifier a voltage signal proportional to the AC magnetic flux through the coil. The second amplifier inputs a current signal to the second conductor half so as to render nonexistent the first amplifier's output voltage signal.

Power frequency electromagnetic field compensation system

A method and apparatus for detecting and deterring underwater threats is provided that uses numerous anodes and sensors around a ship or other waterborne structure to monitor for intruders and issue electrical shocks to the intruders in increasing amounts to deter sabotage. The underwater detection and deterrent system would provide an alarm and the approximate location of the intruder when the electrical field changes in response to the intruder. The system is capable of providing a lethal electrical shock to the intruder if necessary.

Underwater detection and deterrent system

Gradiometers are encompassingly disposed, relative to an object of interest, in a configuration generally describing a closed prolate spheroidal shape, and the measurements taken by the gradiometers are mathematically processed. The gradiometric measurements are defined as directional derivatives which exist in equations involving directional derivatives and prolate spheroidal multipole moments of said entity. The prolate spheroidal multipole moments are thereby calculated, and these prolate spheroidal multipole moment values are extrapolated to ascertain the magnetic fields (equivalently expressed, the magnetic signatures) associated with the object and inwardly delimited by the prolate spheroid. The practitioner can optimize such distribution numerically, orientationally and/or positionally by using the equations involving directional derivatives and prolate spheroidal multipole moments. Extraneous magnetic field effects (e.g., applied fields, earth fields) are inherently excluded, thus obviating the object's removal from an electromagnetic test facility.

Gradiometric measurement methodology for determining magnetic fields of large objects

A magnetic field sensor, for sensing the transverse component of the magnetic field intensity H, is based on fluxgate magnetometric principles and includes an &ldquo;E&rdquo;-shaped magnetic core. A drive winding is wound about the medial leg of the &ldquo;E&rdquo; shape. A sense winding is wound about the base of the &ldquo;E&rdquo; shape at the two locations between the medial leg and the extreme legs. A calibration winding is wound about each leg. Another magnetic field sensor, for sensing the normal component of the magnetic induction B, is also based on fluxgate magnetometric principles and includes a magnetic core having a sort of coaxial double cylindrical configuration wherein a basket-shaped cylinder encloses a smaller, solid cylinder. A drive winding, then a sense winding, then a calibration winding are wound over the solid cylinder. During operative placement of either inventive sensor in appropriate relation to a ferromagnetic surface, a closed magnetic flux path is manifested through the sensor and the ferromagnetic material; in effect, the ferromagnetic material is made a part of the sensor's transducer core.

Fluxgate magnetic field sensor incorporating ferromagnetic test material into its magnetic circuitry

A magnetic field sensor based on fluxgate magnetometric principles includes a magnetic core having a highly elongated oblong configuration and accordingly defining a closed magnetic flux path. The core includes flexible amorphous magnetic material. A drive winding is wound about each of two linear sections of the core. The two drive winding-wound linear core sections are closely coupled in parallel adjacent disposition. A sense winding is wound about the drive winding-wound core, thereby forming a narrow unitary strip-like sensor construction which, depending on the embodiment, can be practically any length. Typically, a very long sensor is situated huggingly or abuttingly with respect to a great expanse of a ferromagnetic material surface. The sensor is capable of generating a detectable signal which is representative of the &ldquo;integration&rdquo; of magnetic field components over the length of the core. The invention's integrative function minimizes measurement skewing or distortion attributable to anomalous characteristics of the ferromagnetic material being sensed. The invention's &ldquo;integrative&rdquo; sensor admits of systematic association with any number and diverse kinds of &ldquo;point&rdquo; sensors, in furtherance of more complete data acquisition.

Spatially integrating fluxgate manetometer having a flexible magnetic core

The invention uniquely avails of Fourier analytical principles for determining the distribution of a magnetic field in a one-dimensional (linear), two-dimensional (planar) or three-dimensional (spatial) region of interest. According to many embodiments, integrating sensor apparatus having an associated length is inventively implemented so as to measure the magnetic field amplitude value for each of two or more different points. Alternating current is applied at at least one high frequency whereby, for each such frequency, the associated wavelength corresponds to some multiple of the sensor's length. Coiled around the sensor is/are one or more solenoids which is/are configured so as to establish a standing wave along the sensor's length. Inventive adaptation of the sensor's integrating function basically entails regarding a Fourier-type harmonic bias function as being consequential of the standing wave. A Fourier coefficient is thus inventively found for each selected multiple of the sensor's length. The invention is especially advantageous because a single inventive sensor is capable of measuring a magnetic field distribution of virtually unlimited expanse, the extensiveness of which would conventionally require a multiplicity of arrayed sensors.

Standing wave magnetometer

A magnetic field sensor based on fluxgate magnetometric principles includes a magnetic core having an elongated oblong configuration and accordingly defining a closed magnetic flux path. The core includes a rigid bobbin which defines the core's shape, and about which amorphous magnetic material is wrapped. A drive winding is wound about each of the two parallel linear sections of the core. A sense winding is wound about another rigid bobbin which surrounds the drive winding-wound core. Typically, a feedback winding is wound about another rigid bobbin which surrounds the sense winding. When, for sensing purposes, the driven sensor is situated near and parallel to a ferromagnetic material surface, the sensor is capable of generating a detectable signal which is representative of the &ldquo;integration&rdquo; of magnetic field components over the length of the core. The invention's integrative function minimizes measurement skewing or distortion attributable to anomalous characteristics of the ferromagnetic material being sensed.

Integrating fluxgate magnetometer

The static magnetic field signature of a sea-going vessel is reduced by sly of degaussing current to pairs of loop coils adjacent to the port and starboard sides of the vessel hull. The coils of each pair are positioned at equal angles to a vertical plane extending longitudinally along the keel of the hull. The degaussing currents in the respective coils of each pair are simultaneously varied with respect to amplitude and polarity in accordance with geometrical heading of the vessel and changes in its roll and pitch orientations.

Advanced degaussing coil system

A system and method are provided for degaussing a vessel moving over an urwater magnetic detector. A location at the vessel residing over the magnetic detector is continuously provided to a controller. The vessel is equipped with a plurality of degaussing coils such that each is independently controllable. Degaussing coil currents are determined by the controller according to a least squares minimization routine such that an off-board magnetic field of the vessel at the location over the magnetic detector is absolute zero. In addition, the determined coil currents minimize the off-board magnetic field of the vessel at all other locations. The determined coil currents are then applied to the appropriate degaussing coils via separate power supplies.

Growing community of inventors

Columbia, MD, United States of America

John J Holmes