Laplace gravity gradiometer

• US 5,734,104 A
• Filed: 03/25/1997
• Issued: 03/31/1998
• Est. Priority Date: 08/16/1993
• Status: Expired due to Fees

• Current Assignee: Jerry R. Panenka
• Original Assignee: Jerry R. Panenka
• Inventors: Panenka, Jerry R.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US08/823,833
• Time in Patent Office: 371 Days
• Field of Search: 73/382 G, 73/382 R, 364/420
• US Class Current: 73/382.00G
• CPC Class Codes: G01V 7/00 Measuring gravitational fields or waves; Gravimetric prospecting or detecting

Abstract

A gravity gradiometer capable of obtaining the vertical component T_zz of the gravity gradient tensor out of the two horizontal components T_xx and T_yy based on Laplace equation: T_zz =-(T_xx +T_yy) comprises a single disc, and two pairs of radially-oriented horizontal axis accelerometers oppositely-mounted on such disc along respective X and Y axes, each pair being capable of providing, respectively, T_xx =T_x1 -T_x2 and T_yy =T_y1 -T_y2 where T_x1 and T_x2 are the respective outputs of the X axis accelerometers and T_y1 and T_y2 are the respective outputs of the Y axis accelerometers. The gravity gradiometer is also capable of obtaining all five independent components of the gravity gradient tensor based on the above Laplace equation and tensor symmetry as follows: One of the above pairs of horizontal axis accelerometers further comprises tangentially oriented horizontal accelerometers capable of providing by subtraction the T_xy component of the gravity gradient tensor, and an accelerometer module consisting of two horizontal accelerometers aligned with the radially and tangentially oriented combination is mounted at a location on the Z axis of the disc above or below the disc to provide the T_zx and T_zy components by subtracting the values of T_x and T_y, respectively, at that location from average values of T_x and T_y at the disc plane.

Claims

1. A gravity gradiometer providing the vertical component T_zz of the gravity gradient tensor out of the two directly measured horizontal components T_xx and T_yy based on Laplace equation T_zz =-(T_xx +T_yy), comprising:

(a) a support;

(b) two pairs of horizontal axis accelerometers oppositely-mounted on said support along respective X and Y axes, each pair providing, respectively, T_xx =T_xi +T_x2 and T_yy =T_y1 +T_y2 where T_x1 and T_x2 are the respective outputs of the X axis accelerometers and T_y1 and T_y2 are the respective outputs of the Y axis accelerometers, and

(c) signal processing means for combining the outputs of the accelerometers in order to derive corresponding gravity gradients.

2. A gravity gradiometer as defined in claim 1 wherein said support comprises a single disc with said two pairs of accelerometers being radially oriented thereon.

3. A gravity gradiometer as defined in claim 2, providing all five independent components of the gravity gradient tensor based on said Laplace equation and tensor symmetry, wherein one of said two pairs of horizontal axis accelerometers further comprises tangentially oriented horizontal accelerometers providing the T_xy component of the gravity gradient tensor, and further comprising an accelerometer module having two horizontal accelerometers aligned with said radially and tangentially oriented accelerometers and mounted at a location on the Z axis of the disc above or below the disc to provide the T_zx and T_zy components by subtracting the values of T_x and T_y, respectively, at that location from average values of T_x and T_y at the disc plane;

said signal processing means combining the outputs of said accelerometers to derive the corresponding gravity gradients.