The Full Tensor Gravity (FTG) System was developed and manufactured by Lockheed Martin Federal Systems. Bell Geospace owns three systems that can be used for either Air-FTG^® or Marine-FTG^® applications.

The FTG system consists of 3 Gravity Gradiometer Instruments (GGI's). Internal to each GGI is a rotating disk with 2 match pair of accelerometers. The opposing pairs of matched accelerometers are mounted 15 cm apart. The disk rotates at a commanded rate, and gradients are measured by the difference in readings between opposing pairs of accelerometers. The output of all 4 accelerometers are summed together to measure the gradient accelerations with linear accelerations removed. Data is sampled at 128 Hz.

The GGI's are mounted on a 3 gimbaled stabilized platform, oriented at 120 degrees from each other and 54.74 degrees from vertical. For Marine-FTG^® surveys the azimuth gimbal is set to carousel at a commanded rate for improved noise reduction. For Air-FTG^® surveys, the platform is fixed, but the direction of the GGI's is rotated by 120 degrees on alternating survey days for improved noise reduction. Example of rotating GGI

The platform containing the GGI's and the controlling electronics cabinet are mounted on the most stable area of the survey vehicle.