Beyond MAGIC: Evaluation of Novel Sensors and Satellite Formation Flights for Future Gravimetry Missions

Kurzfassung

For more than two decades, satellite gravimetry missions have provided unique data about mass redistribution processes in the Earth system. Ongoing climate change underlines the urgent need to continue uninterruptedly this kind of measurements with enhanced concepts and sensors. Here we focus on performance evaluation of novel accelerometers (ACC) and satellite formation flights. Only electrostatic accelerometers (EA) were utilized in satellite gravimetry missions at Low Earth Orbit (LEO) so far. EAs are one of the limiting factors in current space gravimetry dominating the error contribution at low frequencies, mostly because of the polarization wire that connects the Test Mass (TM) with the electrode housing. One focus of this study is modelling wireless enhanced EAs with laser-interferometric readout, so called "optical accelerometers" and evaluating their performance at LEOs. 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. Optical accelerometry is based on promising results of LISA-Pathfinder which demonstrated the benefit of using optical ACC and UV TM discharge. This allows to sense the non-gravitational accelerations several orders of magnitude more accurate than it is realized in current gravimetry missions. Contrary to electrostatic or optical accelerometry, in Cold Atom Interferometry (CAI), atom clouds act as test masses. The unknown acceleration is calculated from the phase shift of two interfering atomic states of an atom cloud which is manipulated with pulses of two counter propagating laser beams. We model the full circle of gravimetry missions using various software parts: an orbital dynamics software, a software module, mainly developed by IGP, for modelling novel electrostatic and optical accelerometers including the major noise sources, and a software package for gravity field recovery developed at IfE. CAI and hybridized (EA+CAI) ACCs performance analyses were also carried out at IfE. In this presentation, we compare the performance of different novel accelerometers and gradiometers, i.e. enhanced electrostatic, optical, CAI and hybridized (EA+CAI), as well as demonstrate and evaluate alternative satellite formation flights and combination concepts, such as pendulum, Bender and ll-sst with cross-track gradiometry. Improved results of the recovered gravity fields, including the effect of insufficiently known background models for high-frequency mass variations, will be shown for various mission scenarios and sensors.