Designing a Disruption Tolerant Network for Reactive Spacecraft Constellations

Abstract:

Small spacecraft can now support operational agility due to cognitive payloads, tunable duty cycles, and precise attitude control systems that can re-orient the spacecraft and capture images within short notice. When combined with onboard processing and autonomous scheduling software, this agility can significantly increase response rate, revisit time and coverage. In prior work, we have demonstrated an algorithmic framework that combines orbital mechanics, attitude control, scheduling optimization and some preliminary inter-spacecraft communications to plan the time-varying, full-body orientation of agile, small spacecraft in a constellation. The proposed schedule optimization can run autonomously onboard the spacecraft without ground control, or at the ground station with resultant schedules uplinked to the spacecraft for execution. This paper describes the design of the communication module, which is based on Delay/Disruption Tolerant Networking (DTN) for onboard data management and routing among the satellites. The combined framework been applied to representative constellations making targeted measurements of episodic precipitation events and subsequent urban floods. Results on a 24-satellite constellation observing 5 global regions show appropriately low latency in information exchange (average within 1/3rd available time for implicit consensus), enabling the onboard scheduler to observe ~7% more flood magnitude than a ground-based implementation. Both onboard and offline versions performed ~98% better than constellations without agility