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Self-gradient effects for airborne gravity gradiometry

Summary The method by which an airborne gravity gradiometer measures gravity gradients and is stabilised within the aircraft affects the magnitude of the observed gravity gradient due to the nearby masses in the aircraft. To first order, the gravity gradient due to masses within the aircraft can be modelled using point masses. When the centre of mass of the instrument is stationary with respect to the aircraft, self-gradient is caused by rotation of masses about the centre of mass of the instrument resulting in a modest contribution to changes in observed gravity gradient. Movement of the centre of mass of the instrument with respect to the aircraft produces a larger self-gradient signal. In either case, the self-gradient signal correlates well with aircraft motion and can be easily removed from the observations by post-processing without the need for a complex model of the mass distribution within the aircraft.