Planar Electrostatic Gravity Gradiometer GREMLIT

Based on the strong experience acquired through the development of ultra-sensitive electrostatic accelerometers for the GRACE, GOCE and GRACE FOLLOW-ON satellite gravity missions, ONERA is developing a new concept of gravity gradiometer (GREMLIT) for airborne survey. Using a control loop, four proof masses are maintained motionless with respect to the surrounding electrodes. The applied electrostatic forces needed for this control, are linked to the accelerations suffered by each proof mass. Observation of differences in the four proof-mass acceleration outputs inform on the horizontal gravity gradient with an expect accuracy of one Eötvös (10^-9 s^-2) in laboratory. The adaptation of GREMLIT to airborne conditions requires the cancellation of the acceleration gradiometer common-mode, which is done by integrating GREMLIT on a controlled platform. The operability of GREMLIT in aircraft therefore depends on the stabilizer platform ability to retrieve the parasitic aircraft accelerations, which constitutes a real technical challenge. The presentation will emphasize the conception and development of this stabilizer system and the next steps of the project with hopefully, a first mobile acquisition performed by the end of 2023.