Design consideration of a regional enhanced Bender-type formation scenario for Next Generation Gravity Mission

The aliasing error from poor orbital configuration is the major error source under the single polar-pair satellite formation represented by Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) missions. To improve the accuracy and resolution of the current global gravity field models, the optimal Bender-type formation on a global scale for Next Generation Gravity Mission (NGGM) was submitted in 2014, named e2.motion, with a combined inclination of 89°/70°. However, this combined inclination cannot achieve the best quality of regional gravity field in China. Hence, to enhance dataset quality at regional scale, we attempt to propose an optimized Bender-type formation scenario in China through a closed-loop simulation work as follows: (1) Keeping the inclination of the polar pair satellites (ipolar) as 89° to ensure the global observations. (2) Several representative Bender-type formation scenarios are designed, and the combined inclination as 89°/55.7° is considered for the optimized scenario in China via estimating performances of different scenarios in gravity retrieval. (3) Making assessments of the 5-yr monthly gravity field models derived from the scenarios [89°/55.7°], [89°/70°], and [89°] (GRACE-type), respectively. The results show that: (1) The noise reductions of [89°/55.7°] in China are about 42.9%, 47.4%, and 85.1% relative to scenario [89°/70°] and [89°] (with and without Gaussian filter), respectively. (2) The 3-d and 7-d solutions derived from [89°/55.7°] perform better than those of [89°/70°] both in magnitude and distribution, indicating that [89°/55.7°] outperforms [89°/70°] in the short-time interval gravity retrieval. Relative to the GRACE-FO mission or even the planned Mass Change and Geoscience International Constellation (MAGIC) mission, our study reveals that the [89°/55.7°] scenario designed for regional enhancement is able to provide a gravity dataset with higher accuracy and resolution for the low- and mid-latitude regions encompassing China, which will provide a valuable data foundation for future geoscience research.