Abstract: Autonomous optical navigation (OpNav) is expected to play a crucial role to aid in the in-situ determination of spacecraft trajectory. For asteroid missions, the high communication latency with Earth makes feedback guidance intractable and limited in capabilities. The situation becomes worse in the case of constrained uplink bandwidth and unknown physical properties of the target body. Therefore, the significance of an onboard target-relative navigation system is axiomatic. In this work, a novel and feasible framework of visual imagery-based measurements is proposed in support of the upcoming planetary missions. The framework consists of two segments: ground support system (GSS) and onboard feature recognition system (OFRS). In GSS, structure from motion and stereophotoclinometry are integrated for developing topographic models of both entire body and surface areas as navigation features at different image resolutions. OFRS works by rendering the expected appearance of the uploaded feature catalog, which is registered to the onboard collected image. The corrected bearing measurement can then be fed to navigation filter to update the onboard spacecraft knowledge. The application of ICQ model is first proposed for on-orbit extended-body centroid tracking. The amount of data uploaded is only 20% of the conventional model, and the pointing measurement accuracy of 3% of the target diameter in pixels can be achieved. The masked NCC technique was first applied to implement on-orbit feature recognition. It is demonstrated that the computation of masked NCC registration is as accurate as that of the standard NCC registration, while the efficiency can be improved by about 1 order of magnitude. This work describes the principle and performance of the framework, with examples from the previous small body asteroid mission and simulations. The proposed framework enables autonomous and efficient localization of spacecraft. 

Key words: structure from motion, stereophotoclinometry, autonomous optical navigation, asteroid, guidance, navigation and control