Autonomous target asteroid search strategy using optical camera
[Objective]Asteroid research has become a focal point of scientific inquiry in recent years.These celestial bodies have drawn significant scientific and economic interest and pose a potential threat to the Earth's safety.This study addressed the challenges in tracking and analyzing small asteroids or those with limited observational data.These asteroids often have significant errors in their ephemeris information,which makes it difficult for impactors to capture them accurately using only these data.The challenge is compounded when the asteroid remains outside the camera's field of view after adjustments based on the ephemeris positions.Therefore,an efficient and rapid search strategy must be adopted to adjust the camera's direction,ensuring that the asteroid is viewed.[Methods]This research is based on China's inaugural asteroid impact mission.The focus is on the final-stage target search strategies for asteroids with small diameters but significant orbit determination errors,employing optical cameras.A critical challenge in this mission is the high relative speed between the impactor and the target asteroid.This speed necessitates the completion of the entire approach and final impact within approximately 4 000 s.Thus,the search strategy must be time-efficient to fit within these strict temporal constraints.Moreover,the camera used in this mission has certain operational limitations due to the parameters involved.For example,a camera cannot capture images during impactor maneuvering.Furthermore,the captured images must be processed autonomously by the impactor's onboard computer to facilitate autonomous navigation.The camera must operate under the principle of minimal imaging,constrained by the requirement of adequate coverage area to minimize the computational load on the onboard computer and reduce the overall search time.To address these operational challenges,a scanning search strategy is designed to maximize the area covered by each imaging instance.This strategy is developed by considering two critical constraints.First,the total search duration must be less than one-tenth of the entire approach phase,which translates to less than 400 s.Second,the imaging interval must be greater than 0.5 s.The proposed strategy can effectively cover target areas of varying sizes by adjusting the number of searches.This study provides a detailed analytical expression for the achievable area coverage with varying numbers of searches.In addition,a method for recursive calculation is proposed for different field-of-view positions.This methodology is crucial to ensure the adaptability and efficiency of the search strategy in real-time scenarios.Numerical simulation techniques are applied to validate the effectiveness of the proposed search strategy.These simulations are critical for testing the strategy under various conditions and assessing its feasibility and reliability.[Results]The results of these simulations were highly encouraging.The search strategy achieved a 100％success rate,with a maximum duration of 356.2 s and an average duration of 98.3 s.The shortest duration recorded for a single search was approximately 1.5 s.[Conclusions]These results are particularly noteworthy because they demonstrate the strategy's compatibility with the performance of the camera,the computational power of the onboard computer,and maneuvering time constraints.
asteroid explorationasteroid impactoptical searcharea search
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