Recovery of the Earth’s gravity field from formation-flying satellites: Temporal aliasing issues

Abstract

Temporal and mean gravity field models derived from the twin-satellite, leader–follower mission GRACE have provided a new type of information for Earth sciences. In this contribution, we study the potential of various alternative satellite formations for gravity field determination in the post-GRACE era in a simulation environment. In particular, the effects of spherical harmonic truncation and of temporal aliasing in the processing of gravity products from such future formations are investigated.Temporal aliasing is studied based on simulated observations of satellite formation flight (SFF) configurations and simulated errors in short-term background models for the non-tidal atmosphere, ocean masses and the continental water storage. We study the potential improvement of SFF gravity field solutions in terms of spherical harmonics truncation of up to degree/order 100. Furthermore, we simulate the recovery of the hydrological signal from various SFF configurations with and without the contamination of the aliasing errors, which were derived from model differences.We implement full-scale simulations for all scenarios to assess the quality of future gravity products in the form of spherical harmonic models. To this end, we create simulated measurements for four satellite configurations (known as pendulum, the radial Cartwheel, the LISA and the pendulum-3S) besides the GRACE-type configuration as a reference. All simulations are restricted to a time span of one month to limit computation costs.As expected, the gravity field products derived from future SFF configurations may surpass those obtained from GRACE in terms of isotropy of the gravity field. Our study provides detailed results for many scenarios ranging in terms of spherical harmonic truncation to up to 100 for mean and temporal solutions. Furthermore, we show that specific SFF configurations involving radial and cross-track information strengthen the recovery of the gravitational signal; in addition they are able to significantly reduce the aliasing errors appearing in the temporal GRACE gravity field monthly solutions. Following this, we suggest to fly a future mission in pendulum configuration.