A path towards effective exploitation of quantum sensors in future satellite gravity missions

Abstract

Mapping the Earth’s gravity field from space provides valuable insights into climate change, the evolution of the hydro- and biosphere, and seismic activity. Current satellite gravimetry missions have demonstrated the utility of gravity data in understanding global mass transport phenomena, climate dynamics, and geological processes. However, state-of-the-art measurement techniques face limitations due to noise and long-term drift, which propagate into the recovery of Earth’s time-varying gravity field. Quantum sensors, particularly Cold Atom Interferometry (CAI), offer promise for improving the accuracy and stability of space-based gravity measurements. Therefore, CAI has emerged as a promising measurement technique for future gravimetric satellite missions due to its potential for measuring gravitational forces and gradients with high precision and accuracy, particularly at low frequencies (sub-mHz). This study examines the sensitivity of CAI accelerometers and gradiometers to errors in measuring the satellite’s attitude and compares it to that of state-of-the-art traditional electrostatic accelerometers. We explore the low-low satellite-to-satellite and gravity gradiometry concepts and build the respective analytical models of measurements and associated errors. We selected an ambitious scenario for CAI parameters that illustrates a potential path for increasing the accuracy of this type of instrument and its related capabilities for space gravimetry. Two operational modes, concurrent (where a new cloud is generated while another is moved to the interferometric chamber) and sequential (where cloud generation and interferometry happen in the same place), are compared to mitigate the effects of inaccurately known attitude rates on Coriolis accelerations. The sequential mode shows potential to reduce these effects, as the atom cloud initially has zero velocity. Otherwise, the Coriolis effects are dominant in the concurrent operational mode. We additionally consider the impact on attitude uncertainty in the context of errors related to the reference frame rotation from the body to the Earth’s co-rotating frames. In addition to the accuracy of attitude measurement, this aspect also highlights the need for drag-free compensation due to the interplay between imperfect frame rotations and the amplitude of the non-gravitational signal. The CAI configuration considered in this study enables the observation of the time-variable gravity signal in the case of low-low Satellite-to-Satellite Tracking missions. Still, it is insufficient for gravity gradient missions because of the reduced signal amplitude. We find it essential to understand and navigate the inherent technical challenges associated with quantum sensors in order to secure an efficient path towards exploiting this technology to monitor changes in the gravity field.