Assessment of a quantum gravity mission by the space-wise approach in the framework of the QSG4EMT project

Quantum technology is becoming more and more popular in science and applications. For some years now the possibility of equipping a future satellite mission with quantum instrumentation has been investigated to improve the current knowledge of the Earth’s gravity field. In this framework the QSG4EMT project, which is funded by ESA, aims at investigating different mission principles (low-low satellite-to-satellite tracking with one or more pairs, gradiometry, etc.) especially with the aim of retrieving the time variations of the gravity field. One of the processing strategies that are used for this assessment is the so-called space-wise approach, which is mainly based on a least-squares collocation scheme passing through the estimation of gridded values to adapt the noise filtering level to the local characteristics of the static and time-variable gravity field. This approach is naturally used for local/regional solutions, but it can be also applied for global modelling by patching overlapped regional solutions all over the world and then performing a spherical harmonic analysis. In this work, the space-wise approach is used to assess the performances of different mission scenarios of future missions having on board purely quantum or quantum-electrostatic hybrid accelerometers. The focus is both on the estimation of the total water storage and on the comparison of the information retrieved from global and local solutions.