SFB 1128: Relativistic Geodesy and Gravimetry with Quantum Sensors - Modelling, Geo-Metrology and Future Technology (geo-Q)

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Spatial and temporal variations of the Earth’s gravitational field allow unique ways to detect and quantify processes of change in the Earth system and to monitor contributions related to climate change. Gravitational data enable the direct quantification of mass changes, such as the present mass loss of the polar ice sheets, the mass component of sea level rise, and changes in the large and small-scale water cycle. However, the gravitational signals obtained from current satellite measurements do not have the resolution and accuracy to reliably identify the causes, mechanisms, and interactions of the processes.The goal of geo-Q is to explore new frontiers of the determination of the gravitational field based on revolutionary quantum sensors and modelling methods from Einstein’s theory of General Relativity. geo-Q will investigate three central components of integrated gravity modelling and develop three fundamentally new geodetic measurement techniques:1.Laser interferometry for ranging between satellites at the nanometer level of precision. Future satellite gravimetry with such sensors will achieve – through gravitational signals – a global and continuous monitoring of mass changes with a ten times improved accuracy and two times better spatial resolution (200 km or better).2.Rapid and compact atomic gravity sensors for terrestrial measurement campaigns to achieve a local recovery of mass change beyond the limit of resolution of satellite techniques.3.Ultra-precise optical atomic clocks for the determination of the gravitational potential from relativistic gravitational frequency redshift. This becomes possible due to the extreme accuracy of today’s clock metrology, and it opens new perspectives to establish a future fundamental reference for gravitational measurements and a globally homogeneous height reference.The integration of the three components will be unique worldwide. In the first funding period we have laid the foundations that we will now apply to real measurements in the field. We will employ our atomic quantum gravimeter for measurement campaigns in northern Germany. After the launch of the GRACE Follow-on mission in early 2018, we will now analyse real data instead of the simulated data that we practiced on in the first period. New compact accelerometers and mobile clocks will facilitate mobile campaigns. And after first tests in the first period, we will now conduct relativistic height measurement campaigns with clock networks.