Interferometric gradiometer apparatus and method

摘要

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.

主权项

1. A gradiometer for measuring a gradient of gravity between two predetermined separated locations by interferometry of first and second light beams, comprising:
first and second test masses which are released for simultaneous freefall solely under respectively different influences of gravity on each test mass at a different one of the two separated locations; and an arrangement of optical elements which directs the first and second light beams into first and second separate and different beam arms respectively, the first beam arm directing the first light beam to impinge upon and reflect from both test masses during the simultaneous freefall of both test masses, the second beam arm directing the second light beam to impinge upon and reflect from both test masses during the simultaneous freefall of both test masses, and wherein an interferometric combination of the first and second light beams delivered from the first and second beam arms after impingement upon and reflection from the test masses contains interferometric information which directly defines the gradient of gravity.