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Lafayette, CO, United States

Micro g LaCoste Inc. | Date: 2012-07-25

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.

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.

Micro g LaCoste Inc. | Date: 2012-08-15

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.

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.

Micro g LaCoste Inc. | Date: 2013-03-12

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.

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