Evaluating the Contributions of Tianwen-1 Orbiter Tracking Data to the Mars Gravity Field Modeling

Abstract Mars gravity field models are critical data sets for studying the planet’s internal structure. Currently, Mars gravity field determination is primarily based on modeling of tracking data from spacecraft such as Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Global Surveyor. The Tianwen-1 mission has now been operational in orbit for over 3 yr. In this study, we construct a degree and order 120 gravity field model using Tianwen-1 spacecraft tracking data from 2021 June to 2024 October and perform a data fusion with the MRO120D gravity field model. Thereafter, we evaluate the contribution of Tianwen-1 tracking data to the improvement of the Martian gravity field modeling. Results indicate that the tracking data from Tianwen-1 provide limited enhancement to the low-degree terms of the gravity field. The relative errors in low-degree terms up to degree 10 of the fused model range from 10 −6 to 10 −4 , and the formal uncertainties up to degree 6 are consistent with those of MRO120F model. The maximum difference in gravity anomalies at the Mars surface reaches 4.5 mGal, while the maximum discrepancy in gravity anomaly errors is approximately 0.65 mGal. The orbit determination performance for the Tianwen-1 spacecraft remains consistent between the two models. Currently, the accuracy improvement in the Martian static gravity field modeling achieved through Earth-based tracking data is relatively modest. Future significant advancements in Martian static gravity field modeling should focus on novel measurement techniques, such as satellite-to-satellite tracking, gravity gradiometry, and an accelerometer on board the spacecraft.