Review of Autonomous Optical Navigation for Deep Space Exploration

Traditional radio-based navigation methods rely on communication with ground tracking networks to achieve deep space navigation. However, as deep space exploration continues to advance, the increasing communication distance leads to increased communication delays, which subsequently diminish the real-time capability and accuracy of the navigation. Furthermore, factors such as obstructions by celestial bodies exacerbate the inadequacy of radio navigation for the navigational demands of deep space exploration. The autonomous optical navigation technology, which primarily employs optical navigation sensors as the core navigation equipment, can obtain navigation information of the current carrier independently of ground tracking networks. It has demonstrated significant advantages in terms of autonomy, real-time capability, reliability, accuracy, and cost-effectiveness, making it an indispensable key navigation technology for deep space exploration. This article initially reviews the fundamental navigation principles applicable to different observation targets and the primary methods for determining navigation states during deep space exploration. It then systematically analyzes the characteristics of optical navigation for the four phases of deep space exploration, namely, transfer, capture, orbital, and landing phases. Finally, using typical missions as examples, this article focuses on the study of optical navigation sensors and algorithms for different phases. The review reveals that optical navigation sensors exhibit distinct characteristics across mission phases. Sensors in the transfer phase typically feature the narrowest field of view with the longest focal lengths and the largest apertures, while those used during the landing phase employ the opposite attributes. For the capture and orbital phases, sensors strike a balance between these extremes. Moreover, the spectrum range predominantly falls within the visible light band. In terms of optical navigation algorithms, various approaches are employed during different phases. Line-of-sight (LOS) navigation is most commonly used in the transfer phase. Compared with the transfer phase, the capture and orbital phases incorporate celestial surface feature navigation, and the landing phase primarily adopts terrain relative navigation (TRN). This article would serve as a valuable reference for promoting the development of autonomous optical navigation technology for deep space exploration.