Abstract: Apparatus for generating an acoustic pulse in a medium wherein an impact piston is driven downwardly along a cylindrical housing by compressed gas to strike a rigid target positioned in contact with the earth. In its firing position, the tapered upper portion of the piston extends above the top of the housing within a container occupied by the compressed gas, the top of the piston being at the same time recessed within a gastight mating enclosure at the top of the container. In this position, the tapered piston surface is constantly exposed to circumferential gas pressure so as to provide a positive breakaway force. Upon release of suitable piston latch means, the piston is first urged downwardly by this breakaway force and thereafter accelerated more powerfully when the top of the piston separates from the enclosure and becomes exposed to gas flow uniformly from all directions.

Abstract: The new invention is a description of a double sideband commutated Doppler microwave system for landing aircraft or spacecraft. It is capable of providing angular information in elevation and azimuth by the measurement of a Doppler frequency in an airborne receiver at a distant point. Furthermore the system has the ability to detect and correct residual multipath errors present in the Doppler signal. It achieves this by the use of an additional beacon signal of known design frequency.The new system is an air-derived navigation system and the main features of its design include the use of two reference radiators, a single moving source along a baseline of radiators, a Doppler signal for deriving angular information, some useful bandwidth economy, a beacon signal for precise multipath error detection and correction and a large time-bandwidth product for averaging errors.

Abstract: An arrangement is provided for correcting the phase and amplitude errors occurring in the quadrature detector of a Doppler radar system. A correction unit (KE) is connected to both analogue-digital converters (AD1, AD2) in the I and Q channels to receive a radar signal which has been received by the system antenna and phase-detected in the quadrature detector (FD1, FD2, FS). The output of the correction unit (KE) is connected to a regulating network (RN) for sensing the output signals from the correction unit (KE) and controlling the latter so that the amplitude and phase errors (a' and .theta.') will be zero.

Abstract: The disclosed device is a marine seismic source which produces a varying FM signal in the low end of the acoustic spectrum. The seismic source uses stiff oscillating radiators to create a signal in the water. These radiators are attached to devices acting as springs with a variable spring rate. Variation of the spring rate as a function of the frequency permits the device to be tuned for maximum power output.

Abstract: A system and method for transmitting enciphered data between first and second terminals over a data transmission channel. The system comprises a transmitter located at the first terminal, a receiver located at the second terminal and cipher computers located at each of the first and second terminals. At least one of the cipher computers is programmable and has a program memory. Storage means are provided for storing a program code or algorithm and a secret cipher key, and means are further provided for transmitting the algorithm to the programmable computer for storage in its program memory. The data transmitted between the first and second terminals is enciphered in accordance with the algorithm stored in the program memory of the programmable computer and determined by the secret cipher key.

Abstract: Devices and methods are disclosed for remote measurment of temperature (and velocity) profiles in a fluid medium (i.e., the atmosphere and/or oceans). Each device, herein called an echometer, and method are capable of providing remote measurements of temperature through the use of propagated waves (i.e., acoustic or electromagnetic waves) and interferometric principles. By use of Doppler processing, simultaneous measurement can be made of three-dimensional velocities at the same points in space to enable remote measurement of heat fluxes in the atmosphere or ocean.

Abstract: The shear wave source of this invention includes a housing and means for applying forces to the shot hole wall. The force applying means applies a number of forces to the shot hole wall along lines normal to a plane close to the shot hole. No pressure waves, but only shear waves are generated at distant points on the plane. At least one of the forces is applied in opposite direction to the other forces to reduce the net recoil of the housing.A first, second and third force are applied at three source points in the observation plane along three lines normal to the plane to generate respectively a first, second and third shear wave in the plane. The first and third forces are equal in magnitude and the second force has twice the magnitude of the first force. The first and third forces are applied along lines in the same direction, but the second force is applied along a line opposite in direction to the lines of the first and third forces.

Abstract: A batteryless, portable, frequency divider including a first LC circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; a second LC circuit that is resonant at a second frequency that is one-half the first frequency; and a transistor coupling the first and second LC circuits for causing the second LC circuit to transmit electromagnetic radiation at the second frequency in response to the first LC circuit detecting electromagnetic radiation at the first frequency. The first and second LC circuits respectively include inductance coils that are positioned orthogonally to one another so as not to be mutually coupled. The frequency divider is operable solely from unrectified energy at the first frequency provided in the first circuit upon receipt of the electromagnetic radiation at the first frequency detected by the first LC circuit.

Abstract: An apparatus for determining the azimuthal direction of a marine streamer cable at selected points along the cable. The apparatus comprises a pod that is clamped to the cable and contains a gimbaled magnetic compass and mean for establishing two-way communication between the pod and the cable.

Abstract: A method for migration of velocity spectra is disclosed wherein migration of common depth point gathers is accomplished without prior determination of the velocity/depth field.

Abstract: An automatic minimum discernible signal level analyzer for evaluating the low signal level detecting capabilities of a pulse-type receiver and including an RF frequency source phase-locked to the radar transmitter frequency and capable of being adjusted in power output by circuitry which automatically measures the statistical noise content of the receiver video and adjusts the power output of the RF source so that the video signal meets preset values of probability of false alarm and probability of detection, the absolute RF power being then a direct measure of the minimum discernible signal sensitivity of the receiver under test.

Abstract: A marine seismic streamer cable having both pressure responsive and acceleration responsive transducers disposed therein. The accelerometer responds to acceleration along one axis regardless of its orientation about the other axis. The accelerometer is mounted in the streamer cable and responds to accelerations produced by a seismic source but is insulated from the noise and motion produced as the streamer cable is towed through the water.

Abstract: In seismic exploration a method for improving seismogram displays is disclosed wherein seismograms having an offset which produces poor signal power are muted and seismograms having offsets with high signal power are stacked. The signal power in a CDP set is determined as a function of different values of assumed acoustic velocity of the earth. This signal detection is repeated for successive values of travel time and offset. The maximum signal power is plotted for values of velocity as a function of travel time and for different ranges of offset to form contours of the maximum signal power as a function of time and offset.

Abstract: A method is provided of ascertaining the far field signature of an array of sound source units, each of which is small compared with the wavelength of the highest frequency of interest. The units are fired so that the interactions between them is negligible. This is achieved by firing the units sequentially so that each generates all its significant radiation before the next is fired, and/or by firing more than one unit at a time and separating the units by at least one wavelength of the lowest frequency of interest. The far field signature of each unit is measured by a pressure-sensitive detector close to the unit but in a region where the phase spectrum of the pressure field is independent of azimuth and range. The far field signature of the array is derived from the measured signatures by summation.

Abstract: A geophone marsh case, for use in wetlands, contains a geophone. An electric cable delivers geophone signals to the outside world and provides a means for pulling an emplaced geophone from the mud. The cable is anchored to the marsh case both internally and externally in order to preserve the integrity of a water seal that surrounds the cable in the cable entry port of the marsh case.

Abstract: A method, when practiced, enhances seismic data so as to suppress noise in the seismic data. The seismic data was generated in a conventional manner by at least one receiver apparatus whose position does not substantially change. The method includes combining at least two elementary seismograms to form noise seismograms containing little or none of the desired signal. The number of different noise seismograms so derived is at least equal to the number of elementary seismograms to be combined to form a final seismogram. The probability distribution of noise is determined for each trace of the noise seismograms from the probability distributions of noise in the traces of the noise seismograms. The most probable form of the desired signals is derived from the probability distribution of noise in the traces of the elementary seismograms to provide the enhanced seismic data.

Abstract: A device for the remote control of data out of a drill hole to the earth surface during the operation of a drilling device which comprises a drill bit, a drill string and a pump raising a flushing liquid into the surrounding annular space of the drill hole and downward into flow channels of the drill string, consisting of devices arranged in the drill string for the ascertaining of desired informational data for the conversion of the informational data into a series of electrical control signals for the producing of pressure pulses in the downward directed flow of the flushing liquid as a function of the control signals and for the production of the necessary electrical energy, characterized in such a way that the devices part of a coaxial support within the flow channels of the drill string form a structural unit and are arranged over each other; separated axial sections of the structural unit are grouped and that at least the topmost section of the structural unit is constructed as an independent component

Abstract: A method for improving signal-to-noise ratio in seismic surveying. It involves generating a series of seismic charges at time spaced intervals but at the same location. A single record is made having a time duration sufficient to cover the maximum reflection time of interest plus the total time for the series of charges. And, thereafter, the record is processed by Fourier transform of the single record to the frequency domain and by constructing frequency domain representation of the series of time intervals plus using the latter to superimpose frequency domain representations of the seismic signals resulting from each of the seismic charges. Then the processing includes inversely transforming the superimposed frequency domain representations back to the time domain.

Abstract: Method of coding and decoding messages wherein a basic key and a random message key, which is transmitted prior to the message, are used. Using a plurality of basic keys entails the problem that the proper basic key must be set in the receiving station. In accordance with the present method, the sequence of a portion (II) of the message key and of a number of check characters derived therefrom are coded, prior to the actual message transmission, using the basic key and a different portion (I) of the message key. Decoding in the receiving station is done by using a basic key which is chosen from a group of basic keys, and the different portion (I) of the message key. A test circuit 21 examines whether the decoded check characters correspond to the check characters derived in the receiving station from the decoded portion (II) of the message key. A positive test result indicates that the desired basic key has been found.

Abstract: In seismic exploration a seismic source transmits seismic energy into the earth and seismic detectors record the seismic waves returning to the earth's surface from reflecting subsurface interfaces. The downgoing transmitted seismic energy and the upcoming reflected seismic waves are transformed into the frequency domain, downward continued, and summed to produce a migrated seismic depth section.