Abstract: A gradient of gravity is defined by a change in the optical path length required to maintain equality in optical path lengths of two beam arms which direct light beams to impinge upon and reflect from two freefalling test masses.

Abstract: Continuous measurement indicia between casing collars of a pipe segment of a well bore casing is obtained from signals obtained by sensing innate, persistent and unaltered characteristics, e.g. magnetic permeability, of the pipe segment along its length, and using the signals to perform a downhole function, e.g. a gravity measurement, at an indicated location.

Abstract: A pendulum arm flexure which supports a pendulum bob for oscillation has predictable and reproducible characteristics. Holders retain a specific predetermined length of uniform diameter elongated fiber at ends of the fiber and permit flexing only along a defined length of the fiber between the holders during oscillation. Energy conserving material of the fiber temporarily stores and releases energy when flexing.

Abstract: A gravity value is measured using two light beams which each reflect from both a freefall test mass and a stationary reference test mass which is inertially supported by a long period isolation device. The optical path lengths of the light beams change equally and oppositely in response to gravity and equally in response to disturbances, resulting in cancellation of the undesirable effects of the disturbances by common mode rejection and in a desirable increase in the number of gravity induced measurement fringes, when the two light beams are combined interferometrically.

Abstract: A double pendulum gravimeter accurately measures gravity by transferring aligned mode energy between suspension points of the pendulums to establish equal arcs of oscillation of the pendulums and by sensing oscillation characteristics to establish an accurate gravity value including a correction factor which depends on the arc of oscillation, while absorbing adverse mode energy.

Abstract: Incident differently-polarized light beams are separately directed and combined by one or two corner cube structures, each having one or two walls formed as a beam splitter. One incident light beam is passed, while the other incident light beam is reflected.

Abstract: Continuous measurement indicia between casing collars of a pipe segment of a well bore casing is obtained from signals obtained by sensing innate, persistent and unaltered characteristics, e.g. magnetic permeability, of the pipe segment along its length, and using the signals to perform a downhole function, e.g. a gravity measurement, at an indicated location.

Abstract: A double pendulum gravimeter accurately measures gravity by transferring aligned mode energy between suspension points of the pendulums to establish equal arcs of oscillation of the pendulums and by sensing oscillation characteristics to establish an accurate gravity value including a correction factor which depends on the arc of oscillation, while absorbing adverse mode energy.

Abstract: A pendulum arm flexure which supports a pendulum bob for oscillation has predictable and reproducible characteristics. Holders retain a specific predetermined length of uniform diameter elongated fiber at ends of the fiber and permit flexing only along a defined length of the fiber between the holders during oscillation. Energy conserving material of the fiber temporarily stores and releases energy when flexing.

Abstract: A gravity gradient is measured interferometrically from two polarized light beams having mutually different polarization planes which reflect from opposite surfaces of two freefalling test masses. The two polarized light beams project along matched coincident beam paths and divert from the coincident paths to interact with the freefalling test masses. An enhanced level of common mode rejection of adverse influences arises from traversing the coincident beam paths.

Abstract: A gradient of gravity is defined by a change in the optical path length required to maintain equality in optical path lengths of two beam arms which direct light beams to impinge upon and reflect from two freefalling test masses.

Abstract: A gravity gradient is measured interferometrically from two light beams which each reflect from both of two freefalling test masses. The light beams project in beam arms which remain equal in length as the two test masses freefall except for different effects of gravity on each test mass and any initial relative velocity difference imparted to the test masses. The optical path length of the beam arms also change equally and oppositely during freefall, to amplify the interferometric effect by four times. A high level of common mode rejection eliminates many spurious influences.

Abstract: A test mass used for light beam interferometric gravity characteristic measurement has a center of mass located equidistant and colinear with optical center points of two oppositely reflecting retroreflectors. Rotation of the test mass about its center of mass during freefall changes the path length of the oppositely reflected light beams by equal amounts, thereby achieving common mode cancellation of the effects of test mass rotation when the two reflected light beams are interferometrically combined.

Abstract: A gravity value is measured using two light beams which each reflect from both a freefall test mass and a stationary reference test mass which is inertially supported by a long period isolation device. The optical path lengths of the light beams change equally and oppositely in response to gravity and equally in response to disturbances, resulting in cancellation of the undesirable effects of the disturbances by common mode rejection and in a desirable increase in the number of gravity induced measurement fringes, when the two light beams are combined interferometrically.

Abstract: Incident differently-polarized light beams are separately directed and combined by one or two corner cube structures, each having one or two walls formed as a beam splitter. One incident light beam is passed, while the other incident light beam is reflected.

Abstract: A gravity gradient is measured interferometrically from two polarized light beams having mutually different polarization planes which reflect from opposite surfaces of two freefalling test masses. The two polarized light beams project along matched coincident beam paths and divert from the coincident paths to interact with the freefalling test masses. An enhanced level of common mode rejection of adverse influences arises from traversing the coincident beam paths.

Abstract: A gravity gradient is measured interferometrically from two light beams which each reflect from both of two freefalling test masses. The light beams project in beam arms which remain equal in length as the two test masses freefall except for different effects of gravity on each test mass and any initial relative velocity difference imparted to the test masses. The optical path length of the beam arms also change equally and oppositely during freefall, to amplify the interferometric effect by four times. A high level of common mode rejection eliminates many spurious influences.

Abstract: A test mass used for light beam interferometric gravity characteristic measurement has a center of mass located equidistant and colinear with optical center points of two oppositely reflecting retroreflectors. Rotation of the test mass about its center of mass during freefall changes the path length of the oppositely reflected light beams by equal amounts, thereby achieving common mode cancellation of the effects of test mass rotation when the two reflected light beams are interferometrically combined.

Abstract: A differential gradient of gravity is directly measured from the interferometric combination of two light beams which reflect from pairs of three freefalling test masses. Optical path lengths of two beam arms change relative to one another because of differential gradient of gravity effects the test masses differently simultaneous freefall. The relatively large background of gravity and the gradient of gravity are eliminated from the measurement while simultaneously achieving a high level of common mode rejection of other spurious influences.

Abstract: Gravity measurements from a borehole gravity survey are obtained by continuously moving the gravity meter within the borehole. Movement-induced acceleration errors are quantified and subtracted from the gross measurements from the gravity meter to obtain actual gravity values at a multitude of measurement points within the borehole. Acceleration errors are calculated from the second differential of the true vertical depth of the gravity meter, which is computed measured length and weight and elongation characteristics of a cable which suspends the gravity meter in the borehole, upper and lower tension measurements in the cable, and the topography of the borehole.