Impact of Earth’s Mean Time-Variable Gravity Field Models on Precise Orbits of Altimetry Satellites

Abstract Gravitational forces are the major forces acting on near-Earth orbiting (e.g., altimetry) satellites. We perform a review of Earth’s mean time-variable gravity (TVG) field models developed in the past 23 years (2000–2023). This includes the models developed using CHAMP, GRACE, GRACE-FO, GOCE, SLR (Satellite Laser Ranging), and DORIS measurements. Some of these models contain just secular terms, while more recent models include also periodic (annual and semi-annual) variations of the Earth’s gravity. We show the impact of these models on precise orbit determination (POD) of selected altimetry satellites, namely TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3 at the time interval from 1992 to 2023. The impact of these models is assessed for different orbit parameters as well as the root-mean-square (RMS) and mean values of SLR observation residuals and orbit differences. Furthermore, the impact of these models on altimetry (single- and multi-satellite) sea surface height crossover differences, radial errors, geographically correlated mean errors, and their trends is analyzed. We have found that the CNES RL05MF model derived using data of 1985–2022 performs best among the models tested in this study, particularly for the Jason-3 time span (2016–2023). Using this model reduces the RMS values of SLR observation residuals from 2.56 cm (for pre-CHAMP model GRIM5-C1) to 1.48 cm for this satellite. The RMS values of orbit differences in the radial direction fit within 0.7–0.8 cm for most recent TVG models, while using old GRIM5-C1 would result in 1.9 cm differences. It is important to reprocess regularly Earth’s TVG data covering the longest time span to minimize extrapolation errors of the models.