A mobile absolute gravimeter based on atom interferometry for highly accurate point observations

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The main focus of this work is to provide the geophysical community with a novel type of absolute gravimeter that will have already proven its functionality at on-site measurements and surpasses the precision of conventional field gravimeters by at least one order of magnitude.The portable quantum gravimeter GAIN (“Gravimetric Atom Interferometer”) has been developed at the Humboldt-Universität zu Berlin (HU) and is now subject of a cooperation between the instrument developers at HU and the absolute gravimetry group at the Institute für Erdmessung in Hannover (IfE). Further development of the instrument aims at the application of GAIN in the research field of geophysics. Typical tasks are to study subterranean mass movements (e.g. in tectonically active regions), to discriminate between man-made and natural environmental effects in land hydrosphere, or technical applications such as the monitoring of underground water reservoirs.The main challenges are the understanding and control of systematic effects as well as the improvement of the sensor’s portability and long-term stability. To identify and overcome systematic effects still inherent in the GAIN system, classical state-of-the-art relative and absolute gravimeters (including the IfE’s FG5-220) are used for direct comparisons. This is necessary to account for the continuously varying gravity value, which is mainly due to tides, atmospheric changes and hydrological variations.We plan to demonstrate the functionality, sensitivity and accuracy of the completed instrument in three steps: (A) simultaneous comparisons during the initial two-year development phase: atomic versus classical instrument; (B) a precision experiment in a pumped-storage water reservoir; (C) a geophysical project with GAIN and FG5-220 in the Fennoscandian land uplift area where absolute accuracy is needed.