Real-time online rescheduling for multiple agile satellites with emergent tasks

The emergent task is a kind of uncertain event that satellite systems often encounter in the application process. In this paper, the multi-satellite distributed coordinating and scheduling problem considering emergent tasks is studied. Due to the limitation of onboard computational resources and time, common online onboard rescheduling methods for such problems usually adopt simple greedy methods, sacrificing the solution quality to deliver timely solutions. To better solve the problem, a new multi-satellite onboard scheduling and coordinating framework based on multi-solution integration is proposed. This method uses high computational power on the ground and generates multiple solutions, changing the complex onboard rescheduling problem to a solution selection problem. With this method, it is possible that little time is used to generate a solution that is as good as the solutions on the ground. We further propose several multi-satellite coordination methods based on the multi-agent Markov decision process (MMDP) and mixed-integer programming (MIP). These methods enable the satellite to make independent decisions and produce high-quality solutions. Compared with the traditional centralized scheduling method, the proposed distributed method reduces the cost of satellite communication and increases the response speed for emergent tasks. Extensive experiments show that the proposed multi-solution integration framework and the distributed coordinating strategies are efficient and effective for onboard scheduling considering emergent tasks.