The Habitat Demonstration Unit Core Avionics Software (HDU-CAS) is designed to provide the required functionality for an engineering prototype of a highly autonomous space habitat element, and to provide an opportunity for new software technologies to be tested in an environment that provides that functionality. The HDU itself must provide basic environmental and infrastructure services, while also supporting a variety of integrated subsystems that aid in the fulfillment of space mission operations. The HDU-CAS must then provide complete command and data handling, and intelligent autonomous operations functions of these needed subsystems in all appropriate circumstances (nominal and off-nominal).

The HDU-CAS was designed and implemented using a mixture of open-standard communication products, commercial subsystem diagnostic modeling software, specialized procedural automation scripting software, and a hierarchical structure. The overall design modeled a structure generally compatible with the ARINC 653 Safety Critical Software Specification to ease later integration into a deployed space vehicle compliant with that specification.

The structure of the HDU-CAS consists of a hierarchical arrangement of hardware interface components [called remote interface units (RIUs)], subsystem-specific controllers, and system management components. The overall component connectivity in the distributed computer network is provided by a message-handling middleware between computer assets and a shared memory component with any particular computer. The functional operation of the HDU-CAS consists in the use of the data acquisition, logging, message-handling, and controller components to monitor telemetry and provide manual and automated command paths for subsystem operations. The system management components use the collected data and controller observations to manage habitat-wide operations involving the concurrent control multiple subsystems. Specifically, they identify subsystem faults, isolate the diagnosis to problem components, and execute recovery actions either automatically or under the direction of crew/HDU operators via the crew display and interface.

The HDU-CAS architecture was designed for the highly intelligent autonomous control of spacecraft habitat systems. Many of the subsystems under HDU-CAS control have strong similarity to controlled subsystems common to military systems, autonomous ground vehicles, robots, and process control subsystems encountered in chemical and nuclear plants. Thus, the HDU-CAS architecture and algorithmic approach to structure and autonomy has potential commercial application in a wide variety of process control situations common to large, safety-critical processing operations.

This work was done by Dennis Lawler and Lui Wang of Johnson Space Center. MSC-25087-1