Optical and radio data fusion for spacecraft navigation and geophysical investigations

Interplanetary spacecraft navigation has been mainly accomplished through radio-tracking-based systems that en able the acquisition of precise position and velocity measurements of interplanetary spacecraft with respect to Earth’s ground stations. While effective, during deep space operations near celestial bodies, onboard instruments, including optical cameras, can provide key information for high-precision navigation relative to the surface of the central body. The synergic combination of deep-space radiometric measurements with auxiliary datasets is essential to enhance the spacecraft navigation capabilities and support thorough scientific investigations, addressing the challenging tasks of future planetary missions. Optical measurements constrain the state of the spacecraft relative to surface features on the orbited body, such as craters, which are detected in the images, thereby improving the accuracy of the spacecraft orbit. Radiometric measurements provide constraints along the line-of-sight between the spacecraft and the ground stations. The software developed in this study enables precise processing of optical images by using a machine-learning crater detection algorithm, which identifies the centroid of the observed features. The optical data analysis pipeline includes a crater-matching algorithm that establishes correspondences between the detected craters and those stored in an onboard catalogue, which are projected on the image plane according to a preliminary estimate of the spacecraft position and attitude. The joint processing of radio tracking and optical data in a least-squares batch filter provides robust support for the reconstruction of the spacecraft trajectory. This study presents the outcomes obtained by applying our novel method to combine radio and optical measurements of the Mars Reconnaissance Orbiter mission.