A method for rebalancing a group of accelerometers in a gravity gradiometer instrument (GGI) includes the steps of defining and implementing a number of groupwise actuation constrainment modes based on a design of the gravity gradiometer instrument and its accelerometers. Implementing one constrainment mode comprises differentially scaling and distributing a single electrical current to multiple accelerometers' rebalance circuitry to cancel a specific acceleration effect experienced by the group of accelerometers or gradiometer as a whole. Superposition of a number of such modes enables rebalancing the full acceleration environment experienced by the group of accelerometers, given negligible local differential acceleration effects specific to, say, an individual accelerometer of the assembly. Mathematically, the multiple of constrainment modes are encapsulated by an actuation or constrainment modal influence matrix, arranged one mode per column of the matrix, and the electrical currents of respective modes are encapsulated in a vector listing of currents.

A method for rebalancing a group of accelerometers in a gravity gradiometer instrument (GGI) includes the steps of defining and implementing a number of groupwise actuation constrainment modes based on a design of the gravity gradiometer instrument and its accelerometers. Implementing one constrainment mode comprises differentially scaling and distributing a single electrical current to multiple accelerometers' rebalance circuitry to cancel a specific acceleration effect experienced by the group of accelerometers or gradiometer as a whole. Superposition of a number of such modes enables rebalancing the full acceleration environment experienced by the group of accelerometers, given negligible local differential acceleration effects specific to, say, an individual accelerometer of the assembly. Mathematically, the multiple of constrainment modes are encapsulated by an actuation or constrainment modal influence matrix, arranged one mode per column of the matrix, and the electrical currents of respective modes are encapsulated in a vector listing of currents.

The general field of the invention is that of matter-wave gravimeters. The gravimeter according to the invention comprises at least: means for generating, for capturing and for cooling a cloud of ultra-cold atoms; means of transferring the atoms into a superposition, with equal weights, of a first internal electronic state called state |1>) and of a second internal electronic state called state |2> comprising the application of at least a first microwave field and of a radiofrequency field; means for separating the atoms into two wave packets for a given period of time under the effect of at least a second microwave field, the said separation leading to a phase-shift associated with the local gravitational field; calibration means allowing a “magic” magnetostatic field to be determined for which the difference in energy between the first internal electronic state and the second internal electronic state is independent, to a first order, of the fluctuations of the magnetostatic field.

The general field of the invention is that of matter-wave gravimeters. The gravimeter according to the invention comprises at least: means for generating, for capturing and for cooling a cloud of ultra-cold atoms; means of transferring the atoms into a superposition, with equal weights, of a first internal electronic state called state |1>) and of a second internal electronic state called state |2> comprising the application of at least a first microwave field and of a radiofrequency field; means for separating the atoms into two wave packets for a given period of time under the effect of at least a second microwave field, the said separation leading to a phase-shift associated with the local gravitational field; calibration means allowing a “magic” magnetostatic field to be determined for which the difference in energy between the first internal electronic state and the second internal electronic state is independent, to a first order, of the fluctuations of the magnetostatic field.

A geopositioning system. The geopositioning system includes an accelerometer including three sensing axes, a gyroscope including three sensing axes, and a magnetometer including three sensing axes, and a processing circuit. The processing circuit is configured to calculate a location of the geopositioning system as a latitude, longitude, and altitude with respect to the Earth.

A gyroscope apparatus for a device including an accelerometer and a magnetic component has a gravity vector generator connected to the accelerometer and receptive to acceleration readings therefrom. A magnetic component output generator is connected to the magnetic component and receptive to magnetic component readings. A sensor fusion engine is connected to the gravity vector generator and to the magnetic component output generator, with a gravity vector value and a magnetic field vector value at a first time instance being combined to represent a first orientation value. The gravity vector value and the magnetic field vector value at a second time instance are combined to represent a second orientation value. An orientation rate of change is derived from a difference between the first orientation value and the second orientation value.

An acceleration measuring device is disclosed, for use as a gravimeter or gradiometer for example. The device has a support and a proof mass, connected to each other by at flexures allowing displacement of the proof mass relative to the support. The support defines a space for displacement of the proof mass. The device is configured so that the modulus of the gradient of the force-displacement curve of the proof mass decreases with increasing displacement, for at least part of the force-displacement curve. This is the so-called anti-spring effect. The resonant frequency of oscillation of the proof mass is determined at least in part by the orientation of the device relative to the direction of the force due to gravity. The proof mass is capable of oscillating with a resonant frequency of 10 Hz or less. The proof mass has a mass of less than 1 gram.

An acceleration measuring device is disclosed, for use as a gravimeter or gradiometer for example. The device has a support and a proof mass, connected to each other by at flexures allowing displacement of the proof mass relative to the support. The support defines a space for displacement of the proof mass. The device is configured so that the modulus of the gradient of the force-displacement curve of the proof mass decreases with increasing displacement, for at least part of the force-displacement curve. This is the so-called anti-spring effect. The resonant frequency of oscillation of the proof mass is determined at least in part by the orientation of the device relative to the direction of the force due to gravity. The proof mass is capable of oscillating with a resonant frequency of 10 Hz or less. The proof mass has a mass of less than 1 gram.

An airborne gravity-based transducer is disclosed as two embodiments with similar physical structures but different operating principles. The first design includes a particle acting as an active interface characterized by internal vibrations relating to its de Broglie wave, a resonant cavity for trapping the particle, and a phonon-wave source wherein the de Broglie and phonon waves interact over a junction area. In the second design, mechanical displacements between the transducer elements can be monitored through electromechanical transduction. Both designs include a power source and a biasing circuit for producing an electrical current across the junction, and a sensing system for measuring voltage. Both designs are capable of cancelling slowly-varying gravitational acceleration due to dynamic interaction in motion with the gravitational field and responding to small-scale gravity anomalies. The transducer can be utilized in hydrocarbon exploration to provide information on areas conducive to fluid entrapment in the sedimentary column.

Disclosed is a calibration method for a rotating accelerometer gravity gradiometer, wherein linear motion error coefficients, angular motion error coefficients, self-gradient model parameters and scale factors of the rotating accelerometer gravity gradiometer are calibrated once by changing linear motion, angular motion, and self-gradient excitations of the rotating accelerometer gravity gradiometer. The calibrated linear and angular motion error coefficients are used for compensating for motion errors of the gravity gradiometer online, and the calibrated self-gradient model parameters are used for self-gradient compensation. The calibration method provided by the present invention is easy to operate and not limited by any calibration site, thereby being suitable for programmed self-calibration and realizing an important engineering value.