Simulation-based evaluation of a cold atom interferometry gradiometer concept for gravity field recovery

Karim Douch,Hu Wu,Christian Schubert,Jürgen Müller,Franck Pereira Dos Santos

doi:10.1016/j.asr.2017.12.005

Abstract

The prospects of future satellite gravimetry missions to sustain a continuous and improved observation of the gravitational field have stimulated studies of new concepts of space inertial sensors with potentially improved precision and stability. This is in particular the case for cold-atom interferometry (CAI) gradiometry which is the object of this paper. The performance of a specific CAI gradiometer design is studied here in terms of quality of the recovered gravity field through a closed-loop numerical simulation of the measurement and processing workflow. First we show that mapping the time-variable field on a monthly basis would require a noise level below 5mE/Hz. The mission scenarios are therefore focused on the static field, like GOCE. Second, the stringent requirement on the angular velocity of a one-arm gradiometer, which must not exceed 10-6 rad/s, leads to two possible modes of operation of the CAI gradiometer: the nadir and the quasi-inertial mode. In the nadir mode, which corresponds to the usual Earth-pointing satellite attitude, only the gradient Vyy, along the cross-track direction, is measured. In the quasi-inertial mode, the satellite attitude is approximately constant in the inertial reference frame and the 3 diagonal gradients Vxx,Vyy and Vzz are measured. Both modes are successively simulated for a 239 km altitude orbit and the error on the recovered gravity models eventually compared to GOCE solutions. We conclude that for the specific CAI gradiometer design assumed in this paper, only the quasi-inertial mode scenario would be able to significantly outperform GOCE results at the cost of technically challenging requirements on the orbit and attitude control.

Highlights

The GOCE (Rummel et al, 2011) and GRACE (Tapley et al, 2004) missions have provided unprecedented insights in the static and time-variable gravitational field of the Earth and proved to be very useful in numerous fields, from unification of height systems to the determination of global mass distribution and mass transport in the Earth system (Kusche et al, 2012).The two satellites of the gravimetry mission GRACE (Gravity Recovery and Climate Experiment) are orbiting the Earth since 2002
As expected, √the gravity field model derived from observations with a noise of √7.0 mE/ Hz performs worst while the model derived for a noise of 2.5 mE/ Hz performs best
Vxx w/o emp compute a gravity model based on the three diagonal gravitational gradients of the whole GOCE mission period (November 2009 - October 2013, about 47 months)

Summary

Introduction

The GOCE (Rummel et al, 2011) and GRACE (Tapley et al, 2004) missions have provided unprecedented insights in the static and time-variable gravitational field of the Earth and proved to be very useful in numerous fields, from unification of height systems to the determination of global mass distribution and mass transport in the Earth system (Kusche et al, 2012).The two satellites of the gravimetry mission GRACE (Gravity Recovery and Climate Experiment) are orbiting the Earth since 2002. The GOCE (Gravity field and steadystate Ocean Circulation Explorer) mission delivered data between 2009 and 2013, which allowed to determine the geoid (Torge and Muller, 2012) with an accuracy of about 1 to 2 cm for a spatial resolution of 100 km on the Earth surface. This provided the basis to establish global physical height systems (i.e. those related to the gravity field) and - combined with altimetric measurements of the mean sea surface - to estimate global ocean currents. The core of the GOCE gradiometer consists of 3 pairs of electrostatic accelerometers measuring the differential gravitational accelerations on its sensitive axis with a

Objectives

Results

Conclusion