Evaluation of optical accelerometry for future gravimetry missions

Abstract

More than 20 years of satellite gravimetry missions have provided unique data about mass redistribution processes in the Earth system. Ongoing climate change underlines the urgent need to continue this kind of measurements with enhanced concepts and sensors. Here, we focus on accelerometers (ACC). Drifts of the electrostatic accelerometers (EA) are one of the limiting factors in the current space gravimetry missions dominating the error contribution at low frequencies. The focus of this study is on the modelling of enhanced EAs with laser-interferometric readout, so called 'optical accelerometers' and evaluating their performance at Low Earth Orbit (LEO). Contrary to present-day EAs, which measure capacitively the TM displacement and actuate it electrostatically, optical ACC, beside a similar actuation scheme, track the TM with laser interferometry. Our research is based on promising results of the mission LISA-Pathfinder which demonstrated the benefit of using a drag-free system in combination with optical accelerometry and UV TM discharge which allowed sensing of non-gravitational accelerations several orders of magnitude more accurate than it is realized in current gravity missions. In this presentation, we now introduce a framework for modeling novel EA with laser-interferometric readout mainly developed by IGP including major noise sources, like actuation noise, capacitive sensing, etc. Also, parametrization of the developed ACC model will be discussed including different TM weights and TM-electrode housing gaps. Finally, improved results of the recovered gravity field will be shown for various mission scenarios applying optical accelerometry and gradiometry. This project is funded by: Deutsche Forschungsgemeinschaft (DFG) - Project-ID 434617780-SFB 1464.