Simulation of gravity field estimation of Phobos for Martian Moon eXploration (MMX)

Abstract To study the origin and evolutionary process of the Martian moon Phobos, understanding its internal structure is important. In this study, we simulate the dynamic orbit and gravity field estimation using Doppler, image landmarks, and LIght Detection And Ranging (LIDAR) data based on a mission plan of Martian Moon eXploration (MMX) and investigate whether the differences in the internal density structure of Phobos can be detected through this mission. Degree 2 Stokes coefficients of the Phobos gravity field, C20 and C22, which are necessary to obtain the moment of inertia by combining with the libration amplitude, could be determined at an accuracy of the order 0.1% using datasets from two-dimensional (2D) quasi satellite orbits (QSOs). If observations from 3D QSO could be realized at low altitude, coefficients up to degree and order 5 could be estimated, which could be used to detect regional density anomalies. Moreover, the observation data from the ascending trajectory after landing on the Phobos surface can be used to detect local density anomalies around the landing site, which could help interpret the origin of the samples.