The Autonomous Coordinated Operations Response Network (ACORN) is a state-based approach to FDIR built atop advanced sequencing capabilities currently available in the marketplace. ACORN offers a standardized method for designing, implementing, and running fault protection across disparate spacecraft. The approach uses graphical representations of state machines which manage various subsystems of the spacecraft. The runtime version of state machines coordinate together using guard conditions on transitions. These state machines identify and respond to faults at the component, intermediate, and system levels. Identification of fault conditions is based on telemetry values and sequence global variable values written to by flight software during runtime.
The state-based design of ACORN enforces flight rules and other requirements, operating the spacecraft in a constraint-oriented manner. Responses take the form of spacecraft commands and sequence block invocations, which are implementations found on all spacecraft. Since ACORN runs onboard the spacecraft, it has immediate access to all of the telemetry necessary to detect faults.
ACORN specifications are mission-independent. If a mission lacks a sufficiently powerful sequencing capability to implement the specification, the ACORN process is still extremely useful as a high-level design specification for custom components to be implemented, and allows a standardized capability to be used. Should the target mission feature a sequencing capability with an ACORN translation tool, the specification is automatically translated into an executable set of sequencing components that fully implement the desired detections and capabilities.
4. efficient specification
4. fast response times (on board)
6. emergent behavior
7. low cost
9. layered interfaces
10. iterative process
ACORN is applicable to any space mission performing on-board fault protection. The potential for standardized, inexpensive, extensible, transparent fault protection system using a graphical notation can be targeted at the whole range of LEO, GEO, and interplanetary missions, large and small.
Human spaceflight could utilize ACORN for on-board spacecraft FDIR, allowing the system to autonomously determine faults and issue corrections without the time-consuming intervention of the crew.
ACORN works with any flight software core. It could be applied to non-NASA spacecraft: DoD, NOAA, and ESA missions are prime candidates. Small commercial missions could reduce costs by reducing expensive fault protection personnel time.