Abstract: A GPS single-receiver pointing/attitude system derives pointing/attitude measurements by correlating a selected GPS code (either P or C/A), recovered from GPS navigation signals using a single GPS receiver with multiple GPS antennas (a reference antenna and at least two slave antennas for pointing or three for attitude). For a two antenna pointing application, the GPS receiver (FIG. 4) includes, for each receiver channel, the incoming GPS signals are applied to three code correlators (72-75) assigned to the reference antenna, and three code correlators (76-77) assigned to the slave antenna, which provide corresponding reference and slave I and Q correlation outputs.

Abstract: A global positioning system comprises an RF receiver for receiving L.sub.1, L.sub.2 p-code or ca code modulated frequency outputs from one or more space vehicles, a multiplexer operably connected to the receiver multiplexes the L.sub.1 and L.sub.2 signals to the receiver, and code and carrier tracking loops operably connected to the receiver, each loop including a plurality of filters, one for tracking line-of-sight dynamics and another for determining ionosphere effects on the L.sub.1 and/or L.sub.2 signals.

Abstract: There is disclosed apparatus for controlling the precise time of firing of each air gun in an array of air guns employed in marine seismic exploration. For each air gun in the array, the apparatus maintains a record of past measured gun delays, that is the time period expiring between the triggering of an air gun and the time that the gun actually fires. Upon the receipt of a fire command, the apparatus inserts appropriate delays before triggering the individual air guns. In this way the air guns are controlled to fire in a precise predetermined sequence. The air guns may be caused to fire either simultaneously or sequentially so as to exercise effective control over the spectral content and the directionality of the energy generated by the array.

Abstract: A system of land (field) seismic exploration which eliminates the requirement for a main land cable to transmit seismic data from the sensors to a central recorder is disclosed. The system includes: a seismic source for generating seismic energy; a data acquisition unit for collecting seismic information; and a master control and collating unit for transmitting coded identification and command signals to the source and data acquisition units and collating the data from the individual tapes of the data acquisition units. Each data acquisition unit includes its own controller, sensor group, analog to digital converter, signal conditioner data recorder, and radio frequency receiver. The analog to digital converter includes a plurality of bounded amplifiers to provide a number of fixed gain stages operative throughout a 120 db dynamic range. The signal conditioner includes a large scale integrated metal oxide semiconductor chip processor for performing desired seismic data processing functions.

Abstract: An all digital circuit converts a signal of an unknown frequency into an accurate binary representation of that frequency. The apparatus consists of an all digital closed loop system which has as its input the unknown signal. The closed loop system generates a reference signal and forces the frequency thereof to approximate that of the unknown signal. In so doing, the closed loop generates a binary number representative of the frequency of the reference signal and provides this number as the system output.

Abstract: Disclosed is an improved air gun construction which lends itself to use with a plurality or array of similarly improved air guns which enables easy synchronization and timing of such array of air guns relative to one another. The synchronization and timing is achieved by controlling and monitoring the movement of the shuttle in the air gun. Various sensors are used such as an electrical coil having a constant current flowing therein which produces a flux pattern which is modified when the shuttle is accelerated, thereby inducing a voltage in said coil which is processed by appropriate processing circuitry. Another embodiment employs a magnetic sensor which includes a permanent magnet and coil wrapped therearound; the permanent magnet produces a flux pattern which is altered when the shuttle is accelerated and comes into proximity to the sensing end of said permanent magnet, thereby inducing a voltage in the coil which is then processed in appropriate processing circuitry.