Initial Results from ACCESS: An Autonomous CubeSat Constellation Scheduling System for Earth Observation

We present ACCESS, the Autonomous CubeSat Constellation Earth-observing Scheduling System, which plans constellation operations using both onboard and ground-based algorithms. We discuss the system’s software architecture, which is oriented towards more scalability to constellations of tens to hundreds of satellites and for better performance of data routing to ground. We describe the progress made on an initial version of a greedy data routing algorithm that incorporates crosslink usage. We present results from data routing simulations over a 24 hour planning window with X-band downlinks and optical crosslinks, multiple constellation orbit geometries, and multiple ground station networks. The results show that average data routing latency is improved significantly in most cases when downlinks and crosslinks are used versus only downlinks. A Walker geometry was found to perform best overall in latency, with a reduction from 213 to 23 minutes when using crosslinks for a ground network with 9 stations. We examined latency for urgent, preemptive observations and found that when using crosslinks average latency was reduced to 16 from 25 minutes for Walker. We also examined execution time and found that the algorithm schedules successfully within about 13 real-world minutes for a 100 satellite Walker constellation with crosslinks, demonstrating scalability.