Rotational gravity gradiometer

A rotational gravity gradiometer comprising:

• a first member, a second member, a drive member and a motor;
• the first member disposed above the second member orthogonal to and centered with respect to the second member;
• the first member comprising a first pair of support arms extending axially from a center of the first member;
• the second member comprising a second pair of support arms extending axially from a center point of the second member;
• a mass unit is attached to opposite ends of each support arm at a distal end of the respective first member and second member;
• a first sensor element attached between each mass unit of the first member and a connection point of the second member for sensing movement of the mass unit;
• and a second sensor element attached between each mass unit of the second member and the drive member;
• and
• the drive member coupled to the motor to drive the first member and the second member rotationally;
• wherein the respective first and second sensor elements generate a signal in response to deflection of the support arms induced by an external mass.