Abstract: A device for processing echoes back scattered from the surface of the sea bed in response to sound pulses transmitted by a fish towed while immersed, comprising at least one assembly for determining the components X.sub.C and X.sub.S of the complex envelope of the signals received by a reception chain or from a part thereof, obtained by selective filtering of a narrow band in the frequency spectrum, and computing, storage and display means for obtaining a representation of the variations in time of the complex amplitude of the signals received.

Abstract: The positions of seismic subarrays are determined using special hydrophones in a streamer cable which listen for acoustic signals generated from each seismic subarray.

Abstract: A towed underwater transducer assembly includes a spherical housing (10) suspended from a towing vehicle at the end of a cable (12). The housing includes mounting brackets (26, 28) located less than one-half of the circumference of the housing apart along a meridian of the housing (10) centered in the direction of tow with a bridle cable (24) extending between the mounting brackets including a turnbuckle (32) to adjust its tension and a mechanical stop (30). A grooved pulley wheel (22) is mounted at the end of the towing cable (12) with the bridle cable (24) riding in the groove and the pulley wheel (22) free to seek a position along the bridle cable (24) such that the projected line of the tow cable (12) passes essentially through the geometric center of the spherical housing (10) thereby causing the spherical housing (10) to maintain an essentially vertical orientation irrespective of variations in the speed of tow.

Abstract: Polymer compositions comprising a segmented urethane block polymer and an elastomer having a glass transition temperature between -40.degree. and +15.degree. C. possess a good combination of properties, including relatively high damping and modulus values. Radiation cross-linked tubing prepared from these compositions finds application in the jacketing of marine sonar detection arrays comprising hydrophones.

Abstract: A method is disclosed for locating the position of a marine streamer using two boats and a series of transponders in the streamer. A first pulse is electrically triggered and then generated by the transponders and by a transceiver mounted in the seismic vessel that tows the streamer. These first pulses are detected at a slave ship and the respective distances to the acoustic sources are calculated. The actual locations of the streamer transponders are calculated by trilateration when a second pulse from transponders 2-5 is detected at the slave ship. This second pulse is an acoustically triggered product of an electrically triggered initial pulse generated by a first transponder. This acoustically triggered pulse is used to determine the distance from the seismic ship to the transponder nearest the seismic ship and then to successively further transponders down the streamer length. Thereafter the positions of the transponders may be calculated.

Abstract: A pressure gradient sensor is disclosed for optically sensing the direction and magnitude of an acoustic wave propagating through a fluid. Each sensor consists generally of at least three fiber-optic displacement sensors disposed within a circular array oriented perpendicular to the longitudinal axis of a streamer. Each sensor phase-modulates a coherent light signal indicative of the water pressure sensed outside the streamer. The output of the signals include a component due to transient pressure waves and a component due to hydrostatic pressure differences between the sensors.

Abstract: A method for locating an ocean bottom seismic cable is disclosed wherein a series of shots from a seismic pulse generator are fired. The distance to one seismic pulse detector is determined for each shot defining a spherical surface upon which the detector may be located. The intersection of the spherical surfaces determine the exact location of the detector. Depth detectors may be used to eliminate one half of the possible locations for each shot.

Abstract: A novel configuration of a low-frequency lightweight sonar system is described comprising a coaxial assembly of a transmitting transducer and a directional receiving array contained within a cigar-shaped streamlined cylindrical housing less than 1 ft. diameter which operates in the 3 to 4 kHz frequency region and achieves submarine target detection ranges in the order of 20,000 meters with a bearing accuracy within 2.degree.. The small cylindrical streamlined structural assembly results in a very great reduction in drag resistance while it is being towed underwater at high speeds as compared to conventional sonar domes which must be an order of magnitude larger in diameter to accommodate the larger conventional scanning sonar transducers which are several wavelengths in diameter at the operating frequency.

Abstract: A forward look sonar system in which speed and direction of a sonar platform is obtained. Each acoustic transmission towards the target area over which the platform is traveling is comprised of a plurality of frequencies. A plurality of receiver beams is formed and each individual beam from one transmission is cross-correlated with its corresponding beam from a selected subsequent transmission to derive a delay value. The later received signal for each beam, for each frequency is divided into a plurality of small segments each of which is cross-correlated with a portion of the first return signal corresponding to the same frequency and beam. The cross-correlation functions for the plurality of frequencies for each particular segment are added together to obtain a more precise delay value. The correlation functions for each of the beams are added together and compared to derive a value for platform direction in the intercomparison period and the delay values are utilized to derive a velocity indication.

Abstract: A sonar survey apparatus comprises a submersible vessel having a structure adapted to receive a towing cable. A sonar signal transmitter is mounted on the structure. At least one acoustic reflector is mounted on the structure and is shaped to produce, in a focussing plane, line foci of acoustic echo signals received from remote positions. A line array of receiver transducers are mounted on the structure in the focussing plane and extend in a line substantially at right angles to the line foci. Each receiver transducer element has an output for providing a signal representative of a focussed echo signal. A selector is coupled with the output of each of the receiver transducer elements and has a control input and an output. The selector is operable in response to the control signal to select the output of a receiver transducer element, relating to a predetermined direction, for display.

Abstract: A system for maintaining a substantially constant tension on a towed seismic cable, wherein the instantaneous towing force and the instantaneous cable displacement relative to a fixed shipboard reference are continuously measured and sampled. A microprocessor associated with a servo controlled capstan device, uses those measurements to pay out cable or to retrieve cable in response to an increase or decrease in the instantaneous towing force. The microprocessor also tries to minimize the average cable displacement.

Abstract: A method and apparatus for underwater ranging with the aid of sonic pulses, by irradiating a given transmitting area with sonic energy pulses from a transmitter mounted in a marine vessel, receiving sonic energy echoes reflected from bodies in the transmitting area in a manner which is selective with respect to direction in a plurality of receiving sectors arranged in a fan shape, and associating the received echoes with respective reflection centers within the respective receiving sectors on the basis of associated sonic pulse travel times. Reception is carried out on a second marine vessel different from the vessel carrying the transmitter and which travels at a rearward offset position from the vessel carrying the transmitter at such a distance therefrom that the receiving sectors cover at least part of the given transmitting area, and the azimuthal width of the transmitting area is made very small.

Abstract: The position of a submerged object towed at great depth from a ship is determined, with respect to the ship, from measured values of the travel time of acoustic pulses between the ship and the object. These pulses are emitted at different locations of the ship and received at a point of the object. The values of the travel times of the pulses are measured and digitized on the object and transmitted by cable to the ship where they are processed, in combination with values representing the distances between the emission locations, to determine the coordinates of the object with respect to a system of axes associated with the ship.

Abstract: Selected sections of a seismic streamer cable are provided with an acoustically-triggered compressed gas supply. The acoustic triggering devices associated with each compressed gas supply may be individually addressed by a coded signal. In the event that the streamer cable is severed, the gas supplies of the severed sections of the streamer are used to inflate the jackets of those severed sections so that they will float to the water surface for salvage.

Abstract: A system and method for determining the position of towed marine object relative to a towing vessel. The system comprises a towing vessel, a slave vessel, and the towed object. An acoustic transceiver is located on either the towing vessel or the slave vessel with an acoustic receiver located on the other vessel. One or more acoustic transponders are associated with the towed object. The distance between the towing vessel and the slave vessel is determined, for example, by radio navigation which is calibrated by a high precision range-range system. The acoustic transmitter emits an interrogation signal which causes the transducer(s) to emit a response acoustic signal which is recorded at the two receivers. Using the time for the response signal to reach each of the receivers and the velocity of sound in water, the distance of the transducer from each vessel is calculated. With the three distances the location of the transducer relative to the towing vessel is determined by trilateration.

Abstract: A sonar system comprises a vehicle (1) capable of moving over the bottom of an extent of water, with an emitter of acoustic pulses and a receiver of acoustic energy mounted on said vehicle. Signal processing and display circuitry (e.g. on board a surface vessel 2) are connected to receive signals representative of the acoustic waves emitted by the emitter, of the acoustic waves received by the receiver, and of parameters describing the motion of the vehicle. The signal processing and display circuitry generates an image of objects hidden in the water bottom on the basis of the signals. The emitter of acoustic pulses is provided with at least one parametric transducer having a spot radiation pattern capable of forming a plurality of channels that bathe spots of the water bottom in sound waves, and an electronic pointing system for scanning the channels.

Abstract: Acoustic transponders are attached to sections of a submarine cable for use in accurately locating the cable during deployment or retrieval. An acoustic signal at one frequency, transmitted from the surface or elsewhere, stimulates one of the transponders to generate a first reply signal at a different frequency. The acoustic reply signal generated by each transponder is used to determine the location of that transponder and thus the location of its associated section of the cable. In order to measure cable tension during deployment or retrieval, a strain gauge at each transponder senses the tension of the cable at the location of its associated transponder. After each transponder transmits its first reply signal, it transmits a second reply signal delayed from the first reply signal by a time interval which is controlled by the output of its associated strain gauge.

Abstract: Apparatus for providing a stable platform for equipment to be employed in underwater environment includes a fin assembly for preventing uncontrolled azimuthal motion of the equipment when the fin assembly is suspended in the underwater environment to a level at which a current is present. The equipment is joined to a mounting which is rotatably positioned upon the fin assembly, and is oriented to a selected azimuth by the rotatable mounting in response to control signals received thereby, the fin assembly remaining at a fixed azimuthal orientation determined by the direction of the current as the mounting azimuthally displaces the equipment.

Abstract: An acoustic positioning system locates a marine cable at an exploration site, such cable employing a plurality of hydrophones at spaced-apart positions along the cable. A marine vessel measures water depth to the cable as the vessel passes over the cable and interrogates the hydrophones with sonar pulses along a slant range as the vessel travels in a parallel and horizontally offset path to the cable. The location of the hydrophones is determined from the recordings of water depth and slant range.

Abstract: The output of an auxiliary sensor, such as a magnetometer or metal detector, is recorded along side a sonar trace record, such as from a side scan sonar or sonar sub-bottom profiler, using the same recorder mechanism. In one embodiment, the added information permits correlation on the same chart between sonar generated impressions and local magnetic field disturbances such as produced by magnetically susceptible objects located on or below the seabed. The sonar record is typically provided as a series of adjacent scan lines, intensity modulated in accordance with the intensity of a received sonar echo. A conversion circuit transforms the output of the auxiliary sensor into a format consistent with the sonar scan trace whereby the sensor output is directly reproduced as a part of the sonar trace record, typically at a peripheral edge portion where the sonar image is absent.

Abstract: A method and apparatus for locating and mapping a pool of a pollutant (12) in a body of water (11) comprising the steps of scanning the bottom of said body of water with ultrasonic energy using a transducer (10) periodically pulsed to project pulse envelopes of acoustic energy downwardly to the bottom (14) of the body of water and receiving echo returns from the bottom preceded by echo returns from a reflective interface (13) with a pool of pollutant, if present. The presence of an echo return from an interface (13) as a precursor to an echo return from the bottom indicates the presence of the pool of pollutant at the navigational position of the transducer as the process of scanning continues. Locating and marking the perimeter of the pool permits rapid clean up operations to be directed.

Abstract: A Wide Swath Precision Echo Sounder is provided by means of transmitting grammed acoustic pulses (pings) to insonify a target area and receiving the backscattered energy in two receivers separated vertically. The outputs of each receiver are stored (including phase information) and synthetic aperature outputs are generated. Each space resolution cell will have a phase associated with it for each receiver. Using the interferometer technique, the phase is converted into a depression angle and is combined with the slant range to the particular space cell to provide a numerical measure of the depth and lateral range to the particular spot under consideration.

Abstract: A funnel construction for a dipping sonar system carried in a helicopter includes the opening to a cylindrical housing of glass epoxy material for storing an underwater transducer which is deployed by suspending it into a body of water at the end of a thin cable. The housing opening includes a flared funnel structure including an entrance aperture member of thin wall aluminum alloy, a backing structure including a frustoconical strut member secured to the bottom of the helicopter and a resilient foam material positioned between and bonded to the entrance aperture member and the strut member which permits the entrance aperture member to move somewhat when impacted by the transducer. The aluminum alloy material in the entrance aperture is very light and yet transfers the heat of friction from rubbing of the small diameter cable against itself sufficiently rapidly that very little wear or damage is caused to either the cable or the funnel structure from repeated high speed reeling cycles.

Abstract: Apparatus for monitoring cable tension during submarine laying operations is housed in a separable case suitable for nondestructive attachment around the circumference of a cable at any desired location prior to laying. A strain gauge within the housing is positioned in a saddle across which the cable is placed in a bowed state. The electrical output from the strain gauge, which is proportional to tension in the cable, is translated into an acoustical signal transmissible through a submarine environment. The underwater sound can be picked up by the laying vessel or an assist vessel and displayed in real time. A plurality of tension monitors can be interrogated in sequence or at random under the control of transponder signals from the vessel. The monitor is self-powered and requires no metallic electrical connection to the cable or to the laying vessel.

Abstract: A seismic streamer cable, composed of a plurality of cable sections includes a common transmission line and an internally mounted inductive element in each section. The inductive elements are coupled in parallel to the common transmission line. A plurality of depth transducers, each associated with an inductive pickup, are secured externally to the streamer cable at desired intervals, adjacent to one of the internal inductive elements. A control signal is periodically transmitted through the transmission line and is received, by inductive coupling, at each transducer after a selected delay. In response to the delayed control signal, the transducers inductively launch a depth-proportional signal into the transmission line for reception by a depth readout device.

Abstract: An automatic trolling depth controller is disclosed for a fishing boat employing a downrigger system. A sonar depth indicating unit with a sonar transducer continuously measures changing depth as the boat trolls. A depth control unit is connected thereto which automatically raises and lowers the trolling line via a reversible motor in response to depth indicating signals of the depth indicator unit so as to automatically maintain the end of the trolling line at a substantially constant given spacing from the bottom despite variations in lake depth as the fishing boat trolls.

Abstract: A hydraulically-powered yo-yo reel for handling a marine seismic cable in shallow water. At the beginning of a recording episode, a partially reeled-in seismic cable is released to drift to a standstill behind a ship. Data are recorded. The cable is then accelerated to match the ships's velocity. Following the initial acceleration, the cable is superaccelerated as it is partially reeled in. A microprocessor adjusts a dwell time between recording episodes to compensate for small variations in the ship's velocity.

Abstract: A lightweight high-power transducer employs an axial array of dual-piston transducer element assemblies which are held in concentric alignment within a rigid cylindrical tube by O-rings set into grooves provided in the periphery of the pistons. The pistons have convex shaped vibratile surfaces which, in combination with the sound transmitting fluid which fills the tubular housing, causes each piston to be effectively radiating into an annular shaped tapered horn whose expanding peripheral annular area terminates into a peripheral opening placed in the circumference of the tubular housing. The combination of the inventive transducer with a tricardioid hydrophone results in a lightweight portable sonar system which achieves long-range target detection with a bearing resolution of 5.degree..

Abstract: A seismic survey apparatus comprises circuit arrangements for providing a train of first signals each corresponding to a sound wave transmitted towards the sea bed, and circuit arrangements for providing associated trains of second signals each corresponding to sound waves reflected from the sea bed. Signal storage means are provided for storing the trains of associated second signals. A filter is provided for deriving from the first and associated second signals a control signal indicative of the apparent vertical movement of the surface of the sea bed due to wave motion or swell. The read out from the signal storage means is then controlled in accordance with the control signal to compensate for the apparent vertical movement of the sea bed due to wave motion or swell. Preferably the read out from the signal storage means is controlled by delaying or advancing the read out of the second signal in accordance with the control signal.

Abstract: A cable detecting system with a cable ship, a cable detector towed by said cable ship via a towing wire and said cable detector dredging the water bottom to find a buried cable, has been improved. When the cable detector detects a buried cable, and the cable is engaged with the cable detector, the towing wire between the cable ship and the cable detector is released either by drawing out a wire from the cable ship or by extending an auxiliary wire from the cable detector, thus, the cable detector stops just when a cable is detected, even when the cable ship continues to move by inertia, and no damage is caused to the cable. The presence of a cable is sensed either through a mechanical means which detects the cable by contact between the cable and the detector, or through electromagnetic means. The detection of a cable triggers the above release of the towing wire.

Abstract: An angling machine is electronically controlled with a digital indication of the fishing depth by counting the number of revolutions of the winder or reel spool of the machine. The apparatus comprises a converter for connection to the transmitter and the receiver of an echo sounder, a pulse generator and a plurality of counters being included in the converter for indicating the actual depth as determined by the time interval between two signals from said transmitter and said receiver, respectively, and a plurality of comparators coupled to respective ones of said counters for comparing the counts thereof with the counts of the counters indicating the fishing depth. The angling machine has circuit means controlling the fishing functions thereof by correspondence between the counts of the respective, corresponding counters.

Abstract: A marine cable location system includes a plurality of magnetic compasses located at known spaced intervals along a cable being towed by a marine vessel. These compass readings are recorded along with an onboard magnetic compass reading, an onboard gyrocompass reading, and satellite navigational information. From these recordings, the X-Y coordinates of cable compasses with respect to vessel heading are determined. These X-Y coordinates are recorded along with the vessel's position and heading on magnetic tape and a cathode-ray tube so as to provide a visual display of the cable position with respect to the vessel.

Abstract: The invention concerns acoustic under-water measurement apparatus for determining the location with respect to a surface vessel of objects such as submersible vessels, pipe-riders, mining apparatus, or the like, including tethered submersible vessels. A receiver hydrophone set located on the tethered vehicle receives acoustic reply pulses from sea bottom transponders, telemetering the times of reception to a surface support ship via conductors in the tether cable. Signals obtained at the surface ship directly from the transponders and indirectly via the tether cable conductors are combined aboard the surface ship for computing the positions of both vessels with respect to a base line established by the sea bottom transponders. The system is self-calibrating, so that an expensive survey to determine the actual locations of the bottom transponders is no longer required.

Abstract: A marine depth sounding apparatus including a floatable housing carrying a sonic transducer for emitting sound waves toward the bottom of a body of water and for detecting the reflections of such sound waves, and a sound transmitter for emitting an audible signal when the information provided by the sonic transducer indicates that the depth of the water is less than a predetermined depth. The apparatus may be cast away from the vessel to provide information concerning the depth of water at locations remote from the vessel. A circuit is disclosed for comparing the time period required for sound waves to travel a distance corresponding to the predetermined depth with the actual time elapsed between the emitting of the sound waves by the sonic transducer and their detection by the sonic transducer.

Abstract: A multipoint reflective target system for use as sonar targets. The system ncludes a plurality of small spaced apart reflectors that are interconnected by an elongated flexible tether. The tethered reflectors are then towed in the ocean and form an elongated multipoint reflective target comprising a string of spaced apart reflectors moving under and about parallel to the ocean surface. This target is sonified by a sonar pulse and generates a reflected signal having a predetermined shape. The shape of the reflected signal is determined by a selection of parameters such as the length of sonar pulse, the spacing of the reflectors and the size and material of the reflectors. By properly selecting these parameters it is possible for the multipoint reflective target system to resemble much larger actual or similated targets.

Abstract: This sonar system, placed on a vehicle such as a ship or a submarine, comprises transducer means for transmitting and receiving acoustic waves at two different frequencies, said reception means being adapted to generate echograms of the submerged surface from the received echoes of the transmitted pulses, the directivity diagram of said transducer means comprising a main transmission lobe whose axis is inclined with respect to a vertical line in a plane orthogonal to a first direction of displacement of the vehicle and a second transmission lobe oriented along a vertical line, means for determining the displacement velocity of the ship along said first direction, means for determining the water depth below the vehicle from the measured values of the propagation time of the waves transmitted along the direction of the secondary lobe and means for determining the displacement velocity of the vehicle in a direction orthogonal to the first one, by measuring the frequency of the acoustic waves received along a par

Abstract: 1. Apparatus for protecting a pelagic vessel from attack by acoustic homing orpedoes comprising a vehicle to be towed submerged a substantial distance behind said vessel, an electroacoustic transducer mounted in said vehicle and having a forwardly directed directivity pattern, a source of constant amplitude oscillating electrical wave energy, means for modulating the oscillating frequency of said wave energy cyclically over a range inclusive of the operating frequencies of such torpedoes and at a linear rate slow enough to satisfy the energy requirement in the band pass of passive torpedo circuits and fast enough to satisfy the rise time of active torpedo discriminator circuits, and means for energizing said transducer with the modulated wave energy from said source.

Abstract: A heave compensation system for an underwater towed seismic system of the kind in which a body containing a sound source and hydrophones is towed behind a ship, and a recording is made of echoes from the bottom and sub-bottom layers. An accelerometer in the towed body produces a signal indicative of the vertical acceleration of the body. The acceleration signal is double integrated within a frequency range having a low frequency roll-off to produce a position signal which is used to adjust the firing time of the source. If the fish heaves upwardly, the firing time is advanced; if the movement is downwards, the firing time is delayed. Preferably a pressure transducer in the fish produces a pressure signal which is also used to adjust the source firing time, for pressure variations below the lowest likely wave frequency. The crossover of the pressure and acceleration compensation systems is typically about 0.01 Hz.

Abstract: 1. Apparatus for destroying a ground mine lying proud on the ocean floor prising a self-propelled dirigible underwater vehicle carrying an explosive charge and having a catacoustic system for steering said vehicle in the azimuthal direction of a sound reflecting object, diving control surfaces carried by said vehicle, means for developing a control signal representative of the departure of the vehicle from a selected distance above the ocean floor, means responsive to said control signal for operating said diving control surfaces, and means responsive to a certain change in magnitude of said control signal within a selected time interval for releasing said explosive charge.

Abstract: A time varying gain amplifier for a side scanning sonar system having a predetermined gain versus time relationship is disclosed. The gain is substantially proportional to the square of the elapsed time measured from the last sonar pulse initiating trigger signal. The amplifier in one embodiment employs a series connection of two amplifiers, each of which has a gain which varies linearly with the elapsed time.

Abstract: A charging circuit for a helicopter dipped sonar system in which a single ble conducts sonar and command signals in either direction along with a DC charging current from the helicopter to a storage battery in a submersible sensor unit. A multiplexer and power supply in the helicopter respectively provide simultaneous transmission of command data and charging current over a common conductor to the sensor unit. A filter and demultiplexer positioned in the sensor unit passes only the data for control of a sonar transmitter. The storage battery is charged directly from the conductor and a battery charge indication as well as hydrophone information is combined by a multiplexer at the sensor and returned to the helicopter by the common conductor for data display and power supply control.

Abstract: 1. In a sonic echo system for classifying objects proud on the ocean floor in which a submarine vehicle moves through the ocean at a constant height above the ocean floor, scanning means for simultaneously deriving separate electric signals corresponding to the sonic reflecting values of parallel strips of the ocean floor extending athwartships of said vehicle, means for simultaneously storing said separate signals on a record medium, and means for serially reproducing the stored signals.

Abstract: A marine seismic streamer-cable section includes a plastic tubular jacket reinforced by tough, braided-fiber tapes embedded in the jacket wall. A termination fixture is fastened to each end of the cable section. The termination fixture includes a bulkhead, an untapered end of which fits snugly into the plastic jacket. The other end of the bulkhead is tapered and protrudes from the end of the jacket. Short lengths of the reinforcing tapes are exposed by stripping away some of the jacket wall. A cylindrical wedge grips the exposed tapes between the inner wall of the wedge and the tapered portion of the bulkhead. The tapes are doubled back over the outside of the wedge and are bound to the jacket and to the untapered end of the bulkhead by bands.

Abstract: The navigation system permits remote maneuvering of a water-borne structure about a stationary object by utilizing dual sonar ranging. The structure can be self-propelled or towed by a surface craft. The transducer portion of the navigation system is mounted on the structure and the system's remaining portion is on the deck of the surface craft. For complete remote navigation, at least three but preferably four transducers are employed for positioning at the four corners of a rectangle. Each transducer is both sound-emitting and sound-receiving. The sonic impulses from each pair of port and starboard transducers are directed downwardly and inwardly. The travel time for each reflected sonic impulse is directly proportional to the slant range between the transducer and the object. The spacing between each pair of port and starboard transducers and the frequency of the emitted sound impulses are selected so that very accurate measurements are obtainable of the position of the object relative to the transducers.