Satellite Scheduling Using Directed Acyclic Graphs
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Solution Overview
Problem
Current scheduling systems for imaging satellites face challenges in rapidly updating schedules to respond to changing image acquisition requests and efficiently utilizing resources, particularly in near real-time, while ensuring constraint violations are identified and avoided.
Innovation Solution
The implementation of a system that uses directed acyclic graphs to generate near-optimal schedules for imaging satellites, incorporating crowd-sourced data to identify events of interest and prioritize image acquisition tasks, allowing for automatic generation and updating of schedules without human intervention, and utilizing a machine-to-machine interface to communicate these tasks directly to the scheduling system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual updates are used for satellite scheduling, then schedule accuracy can be maintained, but response time to changing image acquisition requests becomes too slow
Solution Approach 1:
The scheduling system automatically detects constraint violations and removes violating events without human intervention. The system monitors its own schedule, identifies conflicts between cumulative and pair-wise constraints, and self-corrects by removing problematic events, enabling rapid automated response to changing image acquisition requests while maintaining schedule accuracy.
2Reliability
If comprehensive constraint checking is performed after schedule generation, then constraint violations are detected, but scheduling efficiency decreases due to time-consuming verification
Solution Approach 1:
The system performs preliminary constraint checking during the schedule generation process itself rather than as a separate post-processing step. By integrating constraint validation into the creation phase, the system ensures constraint satisfaction while maintaining scheduling efficiency, as violations are identified and resolved during event insertion rather than requiring comprehensive post-generation verification.
3Loss of time
If rapid schedule updates are implemented to respond to changing requests, then response time improves, but schedule optimality deteriorates
Solution Approach 1:
The scheduling system processes image acquisition requests as individual discrete events rather than redesigning entire schedules. When a new request arrives, the system segments the update process by evaluating only the specific new event against existing constraints and schedule, removing only the violating event if necessary. This localized approach enables rapid response while preserving overall schedule optimality by minimizing disruptions to the existing optimized schedule.
4Productivity
If automated scheduling systems are used to improve response time, then productivity increases, but system complexity increases
Solution Approach 1:
The system extracts and separately manages two distinct types of constraints - cumulative constraints (affecting multiple events) and pair-wise constraints (affecting adjacent events). By identifying and removing only the specific constraint type being violated, the system simplifies the automated decision-making process while maintaining comprehensive constraint satisfaction, reducing the complexity of the automated scheduling logic.
Data Source
AI summary
Systems and methods are provided for scheduling objects having pair-wise and cumulative constraints. The systems and methods presented can utilize a directed acyclic graph to increase or maximize a utilization function. Violation of cumulative constraints can be identified at the moment of constraint violation such that events resulting in constraint violations can be removed from the schedule while the schedule is being determined. By removing the events triggering constraint violations at the point of constraint violation, the systems and methods provided can determine optimal or near-optimal schedules in a relatively quick and efficient manner compared to systems and methods that check for violations of cumulative constraints after determining a schedule. The objects can comprise satellites in a constellation of satellites. In some implementations, the satellites are imaging satellites, and the systems and methods for scheduling can use crowd-sourced data to determine events of interest for acquisition of images.