Performance evaluation of the optical navigation electronics of HAYABUSA2

Digital Electronics and Optical Navigation Camera (DE-ONC) is an edge computing node of the asteroid probe HAYABUSA2. DE-ONC was developed to provide real-time image recognition performance for optical navigation. Lightweight, low power consumption and miniaturization are realized to overcome resource restrictions. It also satisfies high reliability and safety requirements of HAYABUSA2 missions. There are static and dynamic requirements for reliability and safety. The former increases reliability by adding redundancy combining the concept of functional distribution and time-division redundancy to meet resource constraints. Functional distribution mode, standby redundancy mode and hot redundancy mode were realized with the same device configuration. The real-time performance of optical navigation exploiting image recognition functions of the unit was demonstrated through the interplanetary cruising phase, as well as touch down to and taking off from the asteroid Ryugu. DE-ONC is always required to operate in the critical operation phase. In addition to that, it must always satisfy latency requirements to complete processing within a predetermined duration and to guarantee hard real-time performance. In order to satisfy these requirements, the image processing unit of DE-ONC adopts a unified language processing system and a distributed memory model with reference to a parallel inference machine, which is a so-called the second generation artificial intelligence technology. Its image processing module integrates a radiation hardened micro-controller unit (MCU) and field programmable gate arrays (FPGAs) with the language processing system and the distributed object model. We report the evaluation result of reliability and safety with real-time performance of the unit's architecture.