Using novel methods based on quantum technology and general relativity provides a major benefit for satellite geodesy, gravimetric Earth observation and reference systems and greatly supports the GGOS (Global Geodetic Observing System) goals in a unique way. These novel concepts include the application of atom interferometry for realizing quantum gravimetry/gradiometry, the enhanced use of laser interferometry for inter-satellite tracking and accelerometry at future gravity field missions, and relativistic geodesy with clocks for the determination of gravity potential differences via gravitational redshift measurements. 

In close collaboration between physics and geodesy, the high potential of quantum technology and novel measurement concepts for various innovative applications in geodesy and geosciences is studied within major research programs like the DFG SFB “Relativistic and Quantum-Based Geodesy (TerraQ)” or the IAG project “Novel Sensors and Quantum Technology for Geodesy (QuGe)”. We briefly illustrate those novel techniques and the beneficial application of the new methods for gravimetric Earth observation in space and on ground such as the direct determination of physical heights and the monitoring of mass variations using clock networks or gravimeters. Realizing these innovative methods is key to quantify climate change processes (groundwater changes, ice mass loss, seal level rise, etc.) with largely increased precision and resolution. 

Gravimetry is becoming increasingly important in various fields of geodesy and the geosciences. It can be used to quantify climate change by measuring changes in mass distribution and can assist in the search for raw material deposits.

Flight gravimetry closes the gap between ground-based gravimetry in small-scale networks and global gravity field determination using satellite gravimetry. Currently, flight gravimetry mainly uses relative gravimeters, but these often have a high drift and limited resolution. In addition, intrinsic filtering is necessary, which leads to phase shift errors. These problems can be mostly reduced or eliminated with quantum gravimeters. So far, the use of quantum gravimeters, including commercially available instruments, has been predominantly static in analogy to classical absolute and superconducting gravimeters. Experiments have already demonstrated their use on slowly and uniformly moving platforms (sea gravimetry) and in airplanes. With the application in flight gravimetry, numerous applications come into reach. This project therefore aims to develop a quantum gravimeter prototype for use in airplanes.

However, the rapid and small changes in the motion of the aircraft superimpose the sought-after gravitational acceleration. Therefore, this must be reconstructed as accurately as possible, which is to be realized in the current project through multiple sensor data fusion enabling the gravitational acceleration to be filtered out.

The project presented aims at the development and operation of an absolute quantum optical sensor on moving platforms for flight gravimetry. The focus here is on the geodetic components and initial simulation results.

The Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometry (CARIOQA) Quantum Pathfinder mission aims at demonstrating a quantum technology-based accelerometer in space as a precursor for a later deployment onboard a satellite gravimetry mission. A dedicated Pathfinder satellite will be launched to demonstrate the technology in space and to raise the technology readiness level of the required systems. A recently concluded Phase A study investigated several additional secondary mission objectives based on Pathfinder satellite data which include gravity field recovery and evaluating accelerometer and orbit data for research on the upper atmosphere. In a currently ongoing Phase B study, these topics will be further investigated. 

Improved knowledge of the upper atmosphere benefits current and future satellite missions for example in mission planning, orbit prediction or improving accelerometer data transplants. In this presentation we focus on this aspect of the CARIOQA Pathfinder mission. We give an overview of current models and their application in our mission studies. Additionally, we present some Pathfinder mission scenarios and our method to evaluate their potential for improving current models in low Earth orbit.

The CARIOQA Quantum Pathfinder mission Phase B study is a joint project by a consortium of industry and university partners, coordinated by the French and German space agencies CNES and DLR under CNES lead. Funded by the European Union (id: 101189541).

M.Schilling(1), L. Biskupek(1), S. Bremer(1) and M. Weigelt(1) for the CARIOQA Consortium

(1) German Aerospace Center DLR, Institute for Satellite Geodesy and Inertial Sensing, Callinstrasse 30b, 30167 Hannover, Germany, (manuel.schilling@dlr.de)

Satellite gravimetry missions have significantly enhanced our understanding of the Earth’s gravity field and its dynamics. It became crucial for geosciences to extend the time series with successor missions, accompanied by reviewing the factors for improvement of the temporal and spatial resolution of the data. The accelerometers on board, measuring the non-gravitational forces, have become a limiting factor on the instrumental side. Here, quantum-based sensors provide a promising technique that could replace or be combined with the commonly used electrostatic accelerometers to advance the measurements. The Cold Atom Rubidium Interferometer in Orbit for Quantum Accelerometry (CARIOQA) initiative in the Horizon Europe funding programme aims to launch a quantum pathfinder mission in order to raise the technology readiness level of a quantum accelerometer and to further pave the way of a future quantum space gravimetry mission. As part of the ongoing Pathfinder Mission Preparation (CARIOQA-PMP) project, among investigations on the instrument and satellite side, the scientific advantages of a quantum accelerometer for geodetic purposes are studied comprehensively. Both the pathfinder mission, a single satellite utilising high-low satellite-to-satellite tracking, and a future quantum space gravimetry mission, a constellation of satellites operating in low-low satellite-to-satellite tracking mode, are analysed. For this purpose, closed-loop simulations combining orbit integration and gravity field recovery are carried out. Based on the results, the performance of the cold atom interferometer can be evaluated and compared with other types of accelerometers, thus identifying its benefits and remaining challenges. We acknowledge the funding by the European Union for the project CARIOQA-PMP (Project-ID 101081775).

Authors: Nina Fletling¹, Annike Knabe¹, Jürgen Müller¹, Matthias Weigelt², Manuel Schilling² (¹Leibniz University Hannover, Institute of Geodesy, Hannover, Germany; ²German Aerospace Center (DLR), Institute for Satellite Geodesy and Inertial Sensing, Hannover, Germany)