| 10 Feb 2026
HUST-Grace2026s: A high-resolution static gravity field product from GRACE and GRACE-FO observations (2002–2025)
Abstract. HUST-Grace2026s is a GRACE-only static gravity field determined by HUST (Huazhong University of Science and Technology). It’s determined based on more than 20 years’ observation data from GRACE (Gravity Recovery and Climate Experiment) and its successor GRACE-FO. The model provides high spatial resolution (up to degree/order 180) for mass distribution monitoring, complementing temporal series like HUST-Grace2024.
This study presents the motivation and key outcomes behind our new static gravity field model, HUST-Grace2026s: (1) Merely adding current GRACE-FO observations offers limited improvement to existing GRACE-only models, due to GRACE-FO’s current orbital altitude. (2) The application of stochastic model based on postfit residual significantly enhances accuracy, reducing cumulative geoid error by up to 66 % at degree 180 compared to the nominal strategy. (3) The benefit of LRI data on static gravity field determination is strongly tied to the strategy for estimating rate terms. (4) Comprehensive internal and external validation confirms that HUST-Grace2026s achieves higher spatial resolution than unregularized solutions and improves accuracy by over 50 % compared to its predecessor, HUST-Grace2016s. This product serves as a benchmark for long-term mass change studies.
The primary model data consisting of potential coefficients representing Earth’s static gravity field, together with secular and annual variations. This data set is identified with the following DOI: https://doi.org/10.5880/icgem.2026.001 (Zhou et al, 2026).
This paper showcases the latest progress of the HUST team in the field of gravity field modeling. HUST-Grace 2026s successfully integrates 23 years of GRACE and GRACE-FO observation data spanning from 2002 to 2025. Both the accuracy and reliability of the model have been significantly enhanced. Incorporating LRI1B data into the static field determination framework is a major highlight of this study, providing a valuable reference for the establishment of cross generational satellite gravity benchmarks.
There may still be room for further exploration regarding the analysis of the LRI contribution. Utilizing the resolution matrix is an effective way to understand the relative contribution of each observation component within the entire solution system. According to the results in Fig. 11, GRACE KBR plays a more dominant role compared to GRACE-FO KBR/LRI for the HUST-Grace 2026s model. This is likely due to the fact that the GRACE KBR data spans 15 years while the GRACE-FO data covers only about 6 years within the timeframe. However, this could easily lead readers to the misconception that the data of GRACE KBR is superior to that of GRACE-FO KBR/LRI. I believe this point needs to be clarified in the text to distinguish between data quantity and data quality. Additionally, I am curious to know what the relative contributions of GRACE-FO KBR and LRI to the static field would be if the calculation timeframe were restricted to the GRACE-FO mission period alone, for example, from January 2019 to June 2023.