JIT planning: an approach to autonomous scheduling for space missions

The purpose of this paper is to report the results of a one-year project aimed at demonstrating the concept of “Just-In-Time” (JIT) Planning. The project is based on existing JPL software: Apgen (a resource-based activity planner), Spice (a library for accessing and processing trajectory information), and DARTS Shell (a Spacecraft attitude control and simulation package). The distinguishing feature of our approach is that planning is done in real time, concurrently with execution. In this way, the planner has access to up-to-date information and is able to accommodate unforeseen variations in Spacecraft, or external conditions. By inserting small amounts of “software glue” between these three components, we achieved a smooth transition from deterministic execution of a time-ordered command sequence to an adaptive system that responds in closed-loop fashion to events predicted by the simulator. The main benefit of this approach is to provide an adjustable level of autonomy, ranging from conventional commanding to full autonomy. A significant by-product of the JIT approach is that it can eliminate the need for detailed Spacecraft models, which are replaced by actual or simulated real-time data