Optical orbit determination for asteroid approach with vision-based range information

Optical measurements are widely used in orbit determination (OD) during the approach phase of an asteroid exploration mission. Optical-only OD suffers from range ambiguity, leading to poor OD performance. This paper proposes a method to improve optical-only OD performance using vision-based range (VBR) measurements. The proposed method doesn’t rely on prior knowledge about the shape or size of the asteroid. The proposed method first calculates the asteroid’s area projected on the image, with which the ratios of ranges from spacecraft to asteroid between different epochs are obtained. Then, VBR measurements are constructed by multiplying the range ratios and the previous range estimations. A linear programming algorithm is developed to filter noises and improve the accuracy of VBR measurements. Additionally, as the VBR measurement relies on both current and previous states, expressions of the covariance are derived to handle the time-series dependency of VBR measurements, which can improve the accuracy and uncertainty quantification capacity. Finally, optimal estimations are obtained using both the angle and VBR measurements in a Kalman filter framework. The proposed method’s performance is validated in the approach phase of the Bennu asteroid. Numerical simulations show that the estimation accuracy and convergence are improved by approximately 37%.