A Novel Three-Observation-Link Satellite Formation for Enhanced Temporal Gravity Field Recovery

Summary

Satellite formation configuration plays a crucial role in formulating the next generation gravity mission aiming at improving the accuracy and spatiotemporal resolution of Earth’s gravity field modeling. For the proposed GRACE-Pendulum (GRACE-P) formation, technical challenges and limited accuracy gains from the third observation link led to the adoption of only two baselines, without incorporating the third link perpendicular to the GRACE-type baseline, resulting in potential limitations in modeling accuracy. With future technological advancements overcoming these constraints, this study first proposes a complete triangular GRACE-Pendulum-full (GRACE-PF) formation, which includes the omitted third link, to explore the upper limit of accuracy achievable with this formation geometry. Building on this, we further introduce a novel satellite formation, namely the Three-Observation-Link (Three-OL) formation, inspired by the Chinese TianQin gravitational wave detection project. While geometrically similar to GRACE-PF, Three-OL does not include a GRACE-type baseline. To systematically evaluate the performance of these formations, a closed-loop simulation experiment was conducted, followed by a comparative analysis of GRACE-P, GRACE-PF, and Three-OL formations in the spectral-spatial domain. Specifically, spatial-domain results show that GRACE-PF outperforms GRACE-P by 28.7 per cent globally, confirming the accuracy contribution of the third link. Three-OL exhibits superior performance to GRACE-PF, with higher accuracy for mid-high degree signals in the spectral domain, and an 11.3 per cent accuracy improvement over land areas in the spatial domain. Furthermore, compared with the mainstream Bender and GRACE formations, Three-OL reduces the residual RMS over land areas by 28.4 per cent and 75.9 per cent, respectively, while also demonstrating improved capability for recovering sub-monthly gravity signals. In summary, this study reveals the accuracy potential of the complete GRACE-P configuration and proposes a novel formation capable of supporting high-precision temporal gravity field modeling. This work provides a feasible and efficient formation design for gravity satellite missions dedicated to Earth’s gravity field detection.