Current Research Projects – Institute of Geodesy

Optical Clocks for Chronometric Levelling (CRC 1464, A04)

We will realise the potential of chronometric levelling by demonstrating off-campus height measurements with the same or better resolution than geometric levelling and the Global Navigation Satellite System (GNSS)/geoid approach can presently achieve, in joint campaigns with project A05. This demonstration will be strengthened by the application of our measurement capabilities to geodetic problems of high relevance through cooperation with the TerraQ projects employing gravimetric and GNSS techniques to e.g. monitor water storage and other mass changes (projects Terrestrial Clock Networks: Fundamental Physics and Applications (C02), Modelling of Mass Variations Down to Small Scales by Quantum Sensor Fusion (C05), and Atmosphere-Ocean Background Modelling for Terrestrial Gravimetry (C06)).

Led by: PD Dr. Christian Lisdat, Prof. Dr. Piet O. Schmidt, Dr.-Ing. Denker

Team: Tim Lücke, Constantin Nauk

Year: 2021

Funding: DFG

Validation of Quantum Gravimeter QG-1 for Hydrology (CRC 1464, C01)

For the groundwater management in central Europe, ground-based gravimetry provides a unique potential to monitor temporal variations in the subsurface water content for local areas. The atomic Quantum Gravimeter-1 (QG-1) of Leibniz Universität Hannover (LUH) is in its final phase of development (A01) and will be ready for geodetic and gravimetric applications latest in 2021. The QG-1 capability will be demonstrated indoor and also in a field application as an advanced absolute gravimeter allowing effectively the surveying of gravity variations due to groundwater changes on the uncertainty level of 10 nm/s².

Led by: Dr.-Ing. Heiner Denker, Dr.-Ing. Ludger Timmen

Team: Dinesh Chebolu

Year: 2021

Funding: DFG

Quantum Gravimetry (CRC 1464, A01)

Within TerraQ we aim to establish atom-chip based Quantum Gravimetry with Bose-Einstein condensates (BECs) and explore its potential for mobile gravimetry. Deploying QG-1 (Quantum Gravimeter) with steadily increasing frequency and performance in measurement campaigns for C01, A05 and C05 will allow us to prove the in-field applicability of the associated methods and demonstrate an operation of QG-1 under varying, rough conditions.

Led by: Dr. Waldemar Herr, Prof. Dr.-Ing. Jürgen Müller, Prof. Dr. Ernst Rasel

Team: Nina Heine, Marat Musakaev

Year: 2021

Funding: DFG

Atmosphere-Ocean Background Modelling for Terrestrial Gravimetry (CRC 1464, C06)

We will focus on the development of global background models of atmosphere and ocean dynamics that are applicable to gravity records taken anywhere at the Earth’s surface. The background models will be split into deformation effects that also consider the laterally heterogeneous rheology of the Earth’s crust, regional-to-global attraction effects of both atmospheric and oceanic mass variability along the strategy outlined by, and the local effects from the direct vicinity of the sensor that are most sensible to the local topographic roughness and that might benefit most from a possible augmentation with barometric observations taken around the gravity sensor.

Led by: Dr. Henryk Dobslaw, Dr.-Ing. Ludger Timmen

Team: Dr. Kyriakos Balidakis

Year: 2021

Funding: DFG

Gravimetric Tides and Gravity Currents in the North Sea

The research group is investigating the gravity and deformation (tilt) effect caused by time variations of the mass distribution in the atmosphere and in the sea. It has to be distinguished between the direct Newtonian attraction effects and indirect loading effects. The latter part is accompanied by a vertical shift and a tilt of the sea floor as well as the land surface, especially along the coast or on islands, because of the elasticity of the solid Earth’s crust. Such a vertical ground displacement is associated with an absolute height change of the gravimeter w.r.t. the geocenter. The combined observation of gravity and tilt changes allows the separation of signals due to attraction and load deformation.

Led by: Dr.-Ing. Ludger Timmen, Dr. Adelheid Weise

Team: Dr.-Ing. Ludger Timmen, Dr. Adelheid Weise

Year: 2018

Funding: IfE, Germany’s Excellence Strategy – EXC-2123 “QuantumFrontiers”

Duration: 2018-2021

Gravimetry at Zugspitze and Wank Mountains (Bavarian Alps, Germany)

The geodetic monitoring of variations caused by Alpine orogency and the diminishing permafrost are undertaken with gravimetric as well as geometric techniques. In addition to IfE (absolute and relative gravimetry, levelling), the Bavarian Academy of Sciences and Humanities (GNSS, levelling, relative gravimetry), the Institute of Astronomical and Physical Geodesy - Technical University of Munich (relative gravimetry) and the Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences (superconducting gravimetry, GNSS permanent geodynamic observatory on the Zugspitze) are involved in the cooperation.

Led by: Dr.-Ing. Ludger Timmen

Year: 2018

Funding: IFE, Germany’s Excellence Strategy – EXC-2123 “QuantumFrontiers”, GFZ Potsdam, TU München, Bayerische Akademie der Wissenschaften

Gravimetric reference network for a 10m atom interferometer

The Very Long Baseline Atom Interferometer (VLBAI) at the Hannover Institute for Technology (HITec) is a physics instrument in which experiments on the interferometry of atoms can be carried out over a free-fall distance of about 10m. These experiments are mainly used for fundamental physics, but gravimetric measurements can also be performed. Due to the large fall distance and the resulting long fall time of the atoms, a future accuracy in the range of 1 nm/s² is anticipated. With classical transportable absolute gravimeters, however, some tens nm/s² are achieved. The VLBAI could therefore be a reference for classical gravimeters. For these experiments and for the evaluation of the error budget, however, knowledge of the local gravitational field is necessary. This will be determined in parallel to the installation of the large-scale instrument and further on by gravimetric measurements and forward modelling.

Led by: Dr.-Ing. Manuel Schilling, Dr.-Ing. Ludger Timmen

Team: Dr.-Ing. Manuel Schilling, Dr.-Ing. Ludger Timmen

Year: 2017

Funding: IfE, SFB-1128, EXC-2123 "QuantumFrontiers"

Duration: 2017-2025

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

Atom interferometers have demonstrated a high sensitivity to inertial forces. The Gravimetric Atom Interferometer (GAIN), developed at Humboldt-Universität zu Berlin, is a mobile atom interferometer based on interfering ensembles of laser-cooled Rb-87 atoms in an atomic fountain configuration. In the continued development state-of-the-art superconductiong gravimeters and laser-interferometer based absolute gravimeters are used for comparisons with and the characterization of GAIN.

Led by: Prof. Dr.-Ing. Jürgen Müller

Team: M. Sc. Manuel Schilling

Year: 2012

Funding: DFG