Irregular Asteroid Gravity Field Measurement Based on Visual Navigation

In this paper, a gravity field measurement method based on visual navigation is proposed within the problem of determining the gravity field of weakly gravitating irregular asteroids without flying around orbit. The optical navigation camera on the spacecraft is used to measure three noncollinear feature points of known positions at intervals to obtain the image information. Then the measured data under different flight trajectories of the spacecraft are processed by the weighted least squares batch processing algorithm to estimate the asteroid gravity constant and spherical harmonic coefficients, and simultaneous estimation is required when the asteroid physical parameters of spin axis direction and angular velocity magnitude are uncertain. The simulation results show that the method has high accuracy and the error of the gravity constant estimation does not exceed 0.2%, which is applicable to the density inhomogeneous objects and can provide reliable gravity field data for asteroid exploration missions.