Patent US3727462A successfully refreshed from Google Patents.
US3727462A
Expired / Lapsed
US
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Motion stabilized gravity gradiometer
Assignee: Arthur D Little Inc
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Filing: 1970-08-07
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Granted: 1973-04-17
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Expires: 1990-08-07
Abstract
Abstract Method and apparatus for measuring gravity gradients directly. Two retroreflectors are caused to experience free flight, and the radiation reflected by these retroreflectors during free flight is directed to a radiation receiver which senses and measures the temporal variations of intensity of the interfering reflected radiation beams. The time rate of change of the frequency of the output signal of the receiver is directly related to the vertical gradient of gravity. The instrument of this invention has means to determine, and if desired correct for, deviations of the optical axis of the instrument from the local vertical, rotational motion of the instrument which will cause undesirable Coriolis accelerations and means to compensate for undesirable horizontal motion. This gravity gradiometer is particularly suitable for use aboard moving platforms such as ships, planes and helicopters.
Inventors
- 👤 R Stone
- 👤 D Sullivan
- 👤 Thuna P Von
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 15:32
CPC Classifications
G; G01; G01V; G01V7/00; G01V7/14
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
380 words
An apparatus for determining the vertical gradient of gravity from a moving platform, comprising in combination a. first retroreflecting means; b. second retroreflecting means; c. first and second holding means adapted initially to retain said first and second retroreflecting means at predetermined vertical levels relative to each other; d. means to release said retroreflecting means from said holding means in a predetermined timed sequence thereby to cause said first and second retroreflecting means to experience free flight; e. radiant energy source means; f. radiant energy receiving means adapted to generate signals proportional to radiant energy received; g. optical means adapted to direct said radiant energy to said radiant energy receiving means by way of said first and second retroreflecting means as they experience said free flight, said optical means including means to effect optical interference between the two beams of radiant energy reaching said radiant energy receiving means; h. means to receive said signals from said radiant energy receiving means and to determine the temporal variations of intensity of the interfering reflected radiant energy beams; i. housing means adapted to define a chamber enclosing said retroreflecting means, said holding means and said means to release said retroreflecting means; and j. angular deviation sensing means adapted to sense systematic angular deviation of said apparatus from a predetermined orientation and to develope error signals, said error signals being proportional to theta I the angular deviation of the axis of said housing from local vertical in any direction, theta EW the angular deviation in an East-West direction of the axis of said housing from the local vertical, and d theta EW/dt the time rate of change of said angular deviation in an EastWest direction; k. horizontal stabilizing platform means supporting said housing means by providing 2 translational degrees of freedom for maintaining it in an essentially fixed relationship with respect to said retroreflecting means during free flight in spite of any acceleration or deceleration of the moviNg platform on which it is located; l. supporting means adapted to impart 2 rotational degrees of freedom to said apparatus; m. feedback means associated with said sensing means adapted to transmit said error signals to said supporting means whereby said systematic angular deviations are continuously minimized; and n. recording means adapted to record said error signals.
Claim 2
Independent Claim
380 words
An apparatus for determining the vertical gradient of gravity from a moving platform, comprising in combination a. first retroreflecting means; b. second retroreflecting means; c. first and second holding means adapted initially to retain said first and second retroreflecting means at predetermined vertical levels relative to each other; d. means to release said retroreflecting means from said holding means in a predetermined timed sequence thereby to cause said first and second retroreflecting means to experience free flight; e. radiant energy source means; f. radiant energy receiving means adapted to generate signals proportional to radiant energy received; g. optical means adapted to direct said radiant energy to said radiant energy receiving means by way of said first and second retroreflecting means as they experience said free flight, said optical means including means to effect optical interference between the two beams of radiant energy reaching said radiant energy receiving means; h. means to receive said signals from said radiant energy receiving means and to determine the temporal variations of intensity of the interfering reflected radiant energy beams; i. housing means adapted to define a chamber enclosing said retroreflecting means, said holding means and said means to release said retroreflecting means; and j. angular deviation sensing means adapted to sense systematic angular deviation of said apparatus from a predetermined orientation and to develope error signals, said error signals being proportional to theta I the angular deviation of the axis of said housing from local vertical in any direction, theta EW the angular deviation in an East-West direction of the axis of said housing from the local vertical, and d theta EW/dt the time rate of change of said angular deviation in an EastWest direction; k. horizontal stabilizing platform means supporting said housing means by providing 2 translational degrees of freedom for maintaining it in an essentially fixed relationship with respect to said retroreflecting means during free flight in spite of any acceleration or deceleration of the moviNg platform on which it is located; l. supporting means adapted to impart 2 rotational degrees of freedom to said apparatus; m. feedback means associated with said sensing means adapted to transmit said error signals to said supporting means whereby said systematic angular deviations are continuously minimized; and n. recording means adapted to record said error signals.
Claim 3
Dependent Claim
22 words
a second platform supporting said first platform on bearing means adapted to give said housing means free movement in a first direction;
Claim 4
Dependent Claim
22 words
a second platform supporting said first platform on bearing means adapted to give said housing means free movement in a first direction;
Claim 5
Dependent Claim
16 words
An apparatus in accordance with claim 1 wherein said supporting means is an actively stabilized platform.
Claim 6
Dependent Claim
30 words
An apparatus in accordance with claim 1 wherein said supporting means is a passively stable platform in which said sensing means and said feedback means are inherently a part thereof.
Claim 7
Dependent Claim
22 words
a third platform supporting said second platform on bearing means adapted to give said housing means free movement in a second direction;
Claim 8
Dependent Claim
22 words
a third platform supporting said second platform on bearing means adapted to give said housing means free movement in a second direction;
Claim 9
Dependent Claim
19 words
driving means to move said first platform in said first direction and said second platform in said second direction;
Claim 10
Dependent Claim
19 words
driving means to move said first platform in said first direction and said second platform in said second direction;
Claim 11
Dependent Claim
16 words
An apparatus in accordance with claim 3 wherein said passively stable platform is a pendulous suspension.
Claim 12
Independent Claim
250 words
An apparatus for determining the vertical gradient of gravity from a moving platform, comprising in combination a. first retroreflecting means; b. second retroreflecting means; c. first and second holding means adapted initially to retain said first and second retroreflecting means at predetermined vertical levels relative to each other; d. means to release said retroreflecting means from said holding means in a predetermined timed sequence thereby to cause said retroreflecting means to experience free flight; e. radiant energy source means; f. radiant energy receiving means adapted to generate signals proportional to radiant energy received; g. optical means adapted to direct said radiant energy to said radiant energy receiving means by way of said first and second retroreflectors as they experience said free flight, said optical means including means to effect optical interference between the two beams of radiant energy reaching said radiant energy receiving means; h. means to receive said signals from said radiant energy receiving means and adapted to determine the temporal variations of intensity of the interfering reflected radiant energy beams; i. housing means adapted to define a chamber enclosing said retroreflecting means, said holding means and said means to release said retroreflecting means; j. horizontal stabilizing means to impart 2 translational degrees of freedom to said housing means whereby said housing means will be maintained in a fixed relationship with respect to said retroreflecting means during free flight in spite of any acceleration or deceleration of the moving platform on which it is located, said stabilizing means comprising
Claim 13
Independent Claim
250 words
An apparatus for determining the vertical gradient of gravity from a moving platform, comprising in combination a. first retroreflecting means; b. second retroreflecting means; c. first and second holding means adapted initially to retain said first and second retroreflecting means at predetermined vertical levels relative to each other; d. means to release said retroreflecting means from said holding means in a predetermined timed sequence thereby to cause said retroreflecting means to experience free flight; e. radiant energy source means; f. radiant energy receiving means adapted to generate signals proportional to radiant energy received; g. optical means adapted to direct said radiant energy to said radiant energy receiving means by way of said first and second retroreflectors as they experience said free flight, said optical means including means to effect optical interference between the two beams of radiant energy reaching said radiant energy receiving means; h. means to receive said signals from said radiant energy receiving means and adapted to determine the temporal variations of intensity of the interfering reflected radiant energy beams; i. housing means adapted to define a chamber enclosing said retroreflecting means, said holding means and said means to release said retroreflecting means; j. horizontal stabilizing means to impart 2 translational degrees of freedom to said housing means whereby said housing means will be maintained in a fixed relationship with respect to said retroreflecting means during free flight in spite of any acceleration or deceleration of the moving platform on which it is located, said stabilizing means comprising
Claim 14
Dependent Claim
34 words
photodetecting means responsive to changes in the position of said housing in said first and second directions respective to said retroreflectors in free flight and adapted to generate signals proportional to said changes; and
Claim 15
Dependent Claim
34 words
photodetecting means responsive to changes in the position of said housing in said first and second directions respective to said retroreflectors in free flight and adapted to generate signals proportional to said changes; and
Claim 16
Dependent Claim
25 words
An apparatus in accordance with claim 5 wherein said rotational stabilizing means is a stabilized platform and said stabilized platform rests upon said moving platform.
Claim 17
Dependent Claim
78 words
means to transmit said signals to said driving means whereby said housing means will be maintained in said essentially fixed relationship; k. systematic error sensing means adapted to sense angular deviation of said apparatus from a predetermined orientation and to develop error signals porporational to theta I, theta EW and d theta EW/dt; and l. rotational stabilizing means adapted to apply said error signals to substantially isolate said apparatus from the forces giving rise to said systematic errors.
Claim 18
Dependent Claim
78 words
means to transmit said signals to said driving means whereby said housing means will be maintained in said essentially fixed relationship; k. systematic error sensing means adapted to sense angular deviation of said apparatus from a predetermined orientation and to develop error signals porporational to theta I, theta EW and d theta EW/dt; and l. rotational stabilizing means adapted to apply said error signals to substantially isolate said apparatus from the forces giving rise to said systematic errors.
Claim 19
Dependent Claim
25 words
An apparatus iN accordance with claim 5 wherein said systematic error sensing means and said rotational stabilizing means are combined in a stable platform means.
Claim 20
Dependent Claim
17 words
An apparatus in accordance with claim 7 wherein said stable platform means is an actively stabilized platform.
Claim 21
Dependent Claim
16 words
An apparatus in accordance with claim 7 wherein said stable platform means is a pendulous suspension.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-16 | 1976-10-16 | 1977-04-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-16 | 1980-10-16 | 1981-04-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-16 | 1984-10-16 | 1985-04-17 | $7700.00 | Window Closed / Lapsed |